A Gold Shaking Table are basically low-capacity machines used as last step in the gold upgrading process. Theshakingtable is a thin film, shear flow process equipment, that separatesparticlegrains of its feed material based on thedifferences in their specific gravity, density, size and shape. Mineral rich particles, from light to heavy and fine to coarse will be sorted by net effective weight. Finely crushed or ground ore material goes as feed mixed with water to form a pulp (mud) andfed as slurry of an average about 2025% of solids by weight onto the highest point of the table deck. The gold tables deck hasa reciprocal movement along its main axis that is given using a vibrator or an eccentric head motion. The table surface is manufactured and fitted with several tapered strips called riffles or grooves, often made with of yellow pine (way back in time that is), low-density polythene or aluminum surfacing.Shaking tables and other thin film separating plant recover finely divided gold under conditions of subcritical laminar and supercritical laminar regimes of flow, which may occur only where there is a very thin depth of fluid.
Agold shaking tables riffles taper downwards in elevation in the direction the gold (and all heavies), precious metals concentrate discharge end of the table. This facilitates the ease with which mineral particles can move transversal to the tables axis or shaker-line, therefore helpingseparation over the complete tablelength. Riffle heights and pattern designs are selected based on the desired and required duty/function expected.
Preparing several size fractions for tabling is usually achieved in a hydrosizer. Ifgold is present in both coarse and finely divided sizings at least three, or perhapsfour separate size fractions must be treated, each under a different set of operatingconditions. Tables operate most efficiently with a closely sized feed. The slurry fansout across a smooth section of the surface until it reaches the riffles. The lighterand very fine particles are washed over the riffles and moved along the riffles by thereciprocating motion imparted to the deck while the heavier particles are held back. The concentrates of heavy mineral and gold are discharged over the end of thedeck. Tailings are washed over the lower edge and a middlings fraction is taken offbetween the lower edge of the concentrate strip and the higher edge of the tailingstrip.
Wash water usage is dependent upon the particle diameter and varies from aslow as 0.7 m/t/h of solids for slime decks, up to 56 m/t/h for coarse solidsseparation. Coarse fractions are usually treated at feed rates of up to 1 t/h using approximately 15 to 20 mm stroke lengths at around 280 rpm (Wilfley table data). Thestroke lengths of finer fractions are reduced to 915 mm with increased speeds ofup to 325 rpm but, because of the corresponding lower film, thickness capacitiesmay fall to around 0.25 t/h. The inclination of the deck is adjusted during operationusing a hand-operated tilting device. It is important following each adjustment toallow the table operation to settle down before making a fresh adjustment. The correct inclination is reached when the ribbon of concentrates is clearly defined andremains steady.
The extreme sensitivity of water depths and corresponding current depths to obtain F = 1, and the use of stationary tables as primary concentrating units, was probably the main reason for the consistently low (R.E. 6065%) gold recoveries of early dredgers. For such table types, the fluid forces are applied to the stream-beds as a whole and ripples form, which keep the sand in orbital motion and provide for the denser particles to sink to the bed. Deposition is most favoured by anti-dune conditions produced by free-surface flow at or near the supercritical state. Such bed forms are in phase with the water surface and are produced in the rapid flow conditions of Froude Number F = 1. In this state of flow, the bed forms of the upper flow regime are stable. Below F = 1 the flow is tranquil and shear forces are reduced. In reviewing recovery distributions of certaindredgers it wasnoted that some coarse gold reported with the tailing after passing through two stages of tabling and that fine gold did not concentrate noticeably down the line.
I consider the gold shaker table to be a shaking sluice box OR self cleaning sluice as they both essentially are classifiers used as heavy gold concentrating devices. Apart from nuggets; generally the valuable minerals like heavy precious metals like platinumandpalladium thatcan berecovered by tables and sluices, are found in one size range (generally the finest) and the waste minerals in another. On agold sluice, large particles (gravel) travel by sliding and rolling over the riffles, with finer particles travelling by saltation. Sand travels by a combination of modes described earlier with some saltation over the riffles.Very fine particles are maintained in suspension by turbulent and inter-particle collision.
Riffles function properly only if in the space between them and the slurry is sufficiently live (turbulent) to reject the lighter particles, but not so lively that the gold cannot settle. On a gold shaker table, those particles are allowed to settle as they will get transported to the other end by the vibrating/shaking back-and-forth motion. Lower grade, light pieces, will be able to escape the table a the riffles becomes shorter along the tables length.Once the particle has started to move, the coefficient of friction changes to a dynamic coefficient of friction. In fact, because the fluid push on the particles is larger at the top of the particle than at the bottom, the particle rolls, largely according to the shape of the particle and according to the speed. At low speeds, the effective friction is the relatively large coefficient of dynamic sliding friction, and at high speeds it is the lower coefficient of rolling friction. The change probably takes place partly continuously and partly discontinuously. As a first approximation, the dynamic coefficient of friction may, however, be regarded as constant.
In a sluice box, the settling of heavy minerals between the riffles requires frequent stirring to prevent the riffle spaces from blinding. This also disturbs the gold, which then moves progressively down-sluice. Frequent clean-ups are needed to avoid excessive loss. Boxes may be used in parallel to avoid loss of production time. One box is kept in operation while cleaning up in the other.
Effect of Deck Roughness: The foregoing analysis is based on the postulate that the deck is perfectly smooth. If the deck is rough, i.e., if it has at its surface some recesses capable of partly shielding fine particles from the rub of the fluid, the slope required to move the particles by either rolling or sliding will be increased. At the same time such an effect, while present also for large particles, may be so much smaller for them as to be imperceptible. The relationship of critical angle to size obtained above will therefore not hold for rough surfaces. The problem is analytically complex and it is nevertheless a problem that might well be explored further if a full insight is desired into the mechanism of flowing-film concentration.
Adjustments are provided in all tables for the amount of wash water, the cross tilt, the speed, and the length of the stroke. The speed of the table ranges usually from 180 to 270 strokes per minute, and the strokes are from 1/2 to 1 1/2 long.
Variations in character of feed require variations in operation. The operators duty is to take care of them by adjusting the tilt, the wash water, and the position of the splitters that control discharge of table into concentrate, middling, and tailing launders. One man may look after 10 to 100 tables, depending upon the regularity of the feed and the difficulty of the task assigned to the table.
A coarse feed can be treated in larger amounts than a fine feed. It would seem that the treatable tonnage increases at least as the square of the average size (theory indicates that it increases as the cube of the particle size).
A roughing operation is preferably conducted on a fully riffled deck. These decks have a greater capacity because the particles are treated throughout the deck in the form of a teetering suspension many particles deep instead of as a restive layer one particle deep. Such decks do not provide flowing-film concentration but some sort of jigging. On the other hand, a cleaning operation is preferably performed on a partly riffled deck.
It is clear that minerals of different specific gravity must be present the greater the spread in specific gravity between minerals, the greater the capacity since that sort of condition permits crowding without considerable penalty.
The effect of locked particles on capacity of tables should also be recognized. These particles behave in a fashion intermediate between that of pure particles of their constituent minerals. It is as if a three-product separation were sought in which one of the products would guide-in specific gravity between the two other.
Table capacity may be as high as 200 tons per 24 hr. on a fully riffled deck 4 by 12 ft. treating minus 3-mm. sulphide ore having a specific gravity of about 3.0 (roughing duty), or 500 tons per 24 hr. But table capacity may be as low as 5 tons per 24 hr., or even less, for fine ore (minus 0.3 mm.) if there is only a small specific-gravity differential between minerals.
Operating a shaking table is cheap as power requirement per table are typically low. Most of the energy is expended to move the deck, which must therefore be as light as is consistent with rigidity. Laboratory gold shaking table testingreport.
There are a few steps that need to be taken in order to get yourgold shaker table to work efficiently. The first step that aspiring gold miners must take would be to make sure that all four corners of the table are level from forward to back. It is very important to anchor the bolts so that the shaking of the gold goes to the table and not through the frame. After you begin running your table, you may need to adjust your table from side to side to maintain an even flow of materials on both sides of the table.
A gold shaker table contains a water access point where you can fill it with clean water, which can be seen right under the control area. Alternatively you can directly fill the tank of the shaker table with clean water. The water access point allows you to connect a clean water system through a garden hose. The valve that is right behind the tank is then turned off and the pump system is not running during the process of running fresh water. When clean washing water is distributed at the top of the table at right angles, particles are moved diagonally across the deck and separate from each other according to their size and density. During the fast shaking process, you will gradually begin to see the separation of materials. For example, when you have dirt and rocks that contain materials like lead, sulfides and gold, because of the varying weights of these different materials, you will see these materials venture off in different directions on the shaker table. The lead and the sulfides will be carried over to the right side of the table while the pure gold will be carried over to the far left side of the table.
There is one term to remember when professional gold miners describe the actions of a gold shaker table. When professional gold miners say that small particles of gold are being carried through the grooves, they are referring to the ripples that you can plainly see on the shaker table. When they say that there is an overflow of materials like Black Pyrrhotite, White Quartz, silver and gold on the grooves, then this is a good thing.
When materials are washed by the clean water they are supposed to drop into 3 hoppers/launders underneath the table. There is a centre launderthat will gather the purest portions of gold while the two outside launders will gather some gold, though not as much.
It is crucial to remember to plug the cable of your shaker table into a GFCI (Ground Fault Circuit Interrupter) outlet. Most shaker tables will not work if they are plugged into any other kind of outlet.
In aPercussion Gold Shaker Table,the work of keeping the pulp in a state of agitation, done by the rakes or brushes in the German and Cornish buddies described above, is affected by sudden blows or bumps imparted sideways or endways to the table. The table is made of wood or sheet metal, the surface being either smooth or riffled.
End-bump tables are hung by chains or in some similar manner, so as to be capable of limited movement, and receive a number of blows delivered on the upper end. These blows are given by cams acting through rods, or else the table is pushed forward against the action of strong springs by cams on a revolving shaft, and then being suddenly released is thrown back violently by the springs against a fixed horizontal beam. The movement of the pulp depends on the inertia of the particles, which are thrown backward up the inclined table by the blow given to the table, the amount of movement varying with their mass, and depending, therefore, both on their size and density. The vibrations produced by the percussion also perform the work of the rakes in destroying the cohesion between the particles, and a stream of water washes them down. The result is that the larger and heavier particles may be made to travel up the table in the direction in which theyare thrown by the blow, by regulating the quantity of water, while the smaller and lighter particles are carried down. These machines yield only two classes of material, headings and tailings. One such machine, the Gilpin County Gilt Edge Concentrator was devised in Colorado, and has displaced the blanket sluices atalmost all the mills at Blackhawk. It consists (Fig. 46) essentially of a cast-iron or copper table, 7 feet long and 3 feet wide, divided into two equal sections by a 4-inch square bumping-beam. The table has raised edges, and its inclination is about 4 inches in 5 feet at its lower end, the remaining 1 feet at the head having a somewhat steeper grade. The table is hung by iron rods to an iron frame, the length of the rods being altered by screw threads, so as to regulate the inclination to the required amount. A shaft with double cams, A, making 65 revolutions per minute, enables 130 blows per minute to be given to the table in the following manner; onbeing released by the cam, the table is forced forward by the strong spring, B, so that its head strikes against the solid beam,C, which is firmly united to the rest of the frame.
The pulp coming from the copper plates is fed on to the table near its upper end by a distributing box, D, and is spread out and kept in agitation by the rapid blows. Thesulphides settle to the bottom of the pulp, and are thrown forward by the shock, and eventually discharged over the head of the table at the left hand of the figure, while the gangue is carried down by the water and discharged at the other end. One machine is enough to concentrate the pulp from five stamps. If the table consists of amalgamated copper plates, it is of some use for catching free gold also, treating about 8 cwts. of ore per hour. This machine is not so effective in saving slimed pyrites as the Wilfley table or the vanners.
Gold shaker tables are environmentally friendly (chemical free) for recovering pure gold as they can play an important part in reducing the use of mercury by gold miners. With gold shaker tables miners dont need to resort to mercury amalgamation or cyanide to recover gold. The filter will constantly need to be removed and cleaned as it will get dirty even after using the table a few times.
Miners can design and construct a basic shaking table out of cheap materials that are affordable in local stores, including a drive mechanism that contains bicycle gears, chains and rubber bands that are made from car tire inner tubes. The drive mechanism for a gold shaker table can be a hand crank or it can contain parts of a motorcycle frame and engine. If one prefers to use a motor for his or her table, either an electric motor or a motor that runs on diesel fuel would be the ideal options.
It is important to keep in mind that there is no one specific way to create your own gold shaker table system. Many professional gold mining organizations will create tables of different shapes and sizes to cater to the needs of their customers. Some shaker table systems will feature machines that can crush hard rocks, which are referred to as jaw crushers. The speeds of shaker table systems will vary as they can shake from hundreds to thousands of pounds of materials per hour.
The RP-4 shaker table is the most widely used and most successful gold gravity shaking concentrating table worldwide, used by small and large mining operations and the hobbyist. The patented RP-4 is designed for separation of heavy mineral and gemstone concentrate. The RP-4 table can process up to 600 (typically 400) lbs. per hour of black sand magnetite or pulverised rock with little to no losses. The RP-4 uses a unique reverse polarity of rare earth magnets, which will cause the magnetite to rise and be washed off into the tails. This allows the micron gold to be released from the magnetite, letting the gold travelling to the catch. The RP-4 is compact and weighs 60 lbs. With a small generator and water tank, no location is too remote for its use. The RP-4 is a complete, ready to go gold recovery machine. THERE ARE NO SCREEN INCLUDED with the small shaking table. Use was reservoirsgreater than 250 gallon and recycle all your water. Only 400 Watt of power drawn by typical pump. The small RP4 gold shaking has a mini deck of 13wide x 36 long = 3.25 square feet of tabling area. The RP-4 is the best and longest selling small miner shaker table still on the market today. With many 1000s of units sold during the last 10 years! Review the RP-4 Operating Manual and Installation Guide lower on this page.
The RP-4 uses a unique reverse polarity of rare earth magnets which will cause the magnetite to rise and be washed off into the tails and allowing the micron gold to be released from the magnetite leaving the gold travelling to the catch.
When assembling the RP-4, it is very important to set it up correctly to get the best recovery. The unit needs to be bolted preferably to a concrete pad or bedrock when in the field. It can be weighted down with seven or eight large sandbags. Wooden stands will set up harmonics and vibrations in the unit. Vibrations will create a negative effect on the concentrating action of the deck and create a scattering effect on the gold. We would strongly advise getting the optional stand to mount it. See a detailed RP4 Shaker Table review.
Once you have the RP-4 mounted or weighted down, you will want to level it, place a level under the machine on the bar running attached to the two mounting legs. Use washers to get a precise level adjustment. Once mounted and leveled, use the adjustment screw to adjust the horizontal slope of the deck. It took me about 10 minutes of playing with the adjustment till you are satisfied the slope angle was where it needed to be. A general rule for good recovery is less grade for the table deck and as much water as possible without scouring off the fine gold particles.
When the table is set, wet down your black sand concentrates with water and a couple drops of Jet-Dry to help keep any fine gold from floating off the table. You are now ready to start feeding the RP-4.
DO NOT dump material into the feed tray. You want a nice steady feed without overloading the table. Use a scoop and feed it steadily. Watch the back where the small gold should concentrate. If you see fine gold towards the middle, adjust your table angle just a bit at a time till it is where it needs to be.
Run a few buckets of black sand tailings that already panned out just in case there might have been some gold left behind. Its a good thing, too, because I pulled almost three pennyweights of gold out of my waste materials. Thats a pennyweight per bucket!
You could run all of you concentrates over this awesome little RP-4 Gravity Shaker Table. Some ran bottles No. 1 and No. 2 over the table a second time and cleaned it up some more, getting out almost all of the sand in No. 1 and removing more than half the sand from No. 2. It was amazing to see a nice line of fine gold just dancin down the table into the bottle. And, to think you were was about to throw away all of that black sand that still had color in it! This machine is small enough for the prospector and small-scale miner who, like me, wants all of the gold for his or her hard work. The 911MPE-RP-4 Gravity Shaker Table is also big enough to clean up bucket after bucket of concentrates from a big operation! The RP4 people came up with the solution for getting all of the gold!
All RP4 shaker tables operate best when firmly secured to a dense solid mounting base. Wooden stands will set up harmonics and vibrations. Dense concrete or solid bedrock is preferred or a heavy braced steel table sitting on concrete. Mount shaker table to solid bed rock if possible when operating in the field. When that is not an option, six or seven sand bags may also be used if concrete or bedrock is not available for mounting.
Place a level on top of the steel bar that extends between the two bolts down mounting feet.Use flat washers installed under either end of the mounting feet for precise level adjustment in the long axis.
At no time should sand or slime be re-circulated back with mill water. Large, calm, surface areas are required to settle slimes. Buckets, barrels or any deep containers with turbulent water will not allow slimes to settle. Tailings should discharge into a tails pond or into a primary holding vessel before entering slime settling ponds. Surface area is more important than depth. A small 10 x 20 ft. settling pond can be installed in about 30 minutes. Shovel a 6 high retainer wall of earth and remove all gravel. Lay a soft bed of sand in the bottom. A small raised wall area (with the top approximately 2 blow water level) should be placed around the pump area. Roll out plastic liner and fill with water. Desert areas require a plastic cover to retard evaporation. Use a 24 wood across pond and lay plastic.
As with ponds, at no time should sand or slime be re-circulated back with mill water. A calm surface is needed in the final two barrels to settle slimes. (In lieu of the last two barrels, the discharge from barrel two may be directed to a settling pond as outlined above.)Turbulent water will not allow slimes to settle. Tailings are discharged into the first container.
A small compact tailings thickener introduces tailings feed at a controlled velocity in a horizontal feed design that eliminates the conventional free settling zone. The feed particles quickly contact previously formed agglomerates. This action promotes further agglomeration and compacting of the solids. Slowly rotating rakes aid in compacting the solids and moving them along to the discharge pipe, these solids are eventually discharged at the bottom of the unit. Under flow from the thickener 60-65% solids are processed through a vacuum filter and a90-95% solids is sent to the tailings area. Tailings thickeners are compact and will replace ponds. A 23 ft. diameter will process flow rates at 800 gpm or 50 tph.
Pine oils and vegetation oils regularly coat the surface of placer gold. Sometimes up to 50% of the smaller gold will float to the surface and into the tails. The pine oil flotation method for floating gold is still in use today. A good wetting agent will aid in the settling and recovery of oil coated gold.
Separation of concentrate from tails Minerals or substances that differ in specific gravity of2.5 or to an appreciable extent, can be separated on shaker tables with substantially complete recovery. A difference in the shape of particles will aid concentration in some instances and losses in others. Generally speaking, flat particles rise to the surface of the feed material while in the presence of rounded particles of the same specific gravity. Particles of the same specific gravity but varying in particle size, can be separated to a certain extent, varying in particle size, can be separated to a certain extent, removing the larger from the smaller, such as washing slime from granular products.
Mill practice has found it advantageous in having the concentrate particles smaller than the tailing product. Small heavy magnetite particles will crowd out larger particles of flat gold making a good concentrate almost impossible with standard gravity concentrating devices. The RP-4 table, using rare earth reverse polarity magnets, overcame this problem by lifting the magnetite out and above the concentrate material thus allowing the magnetite to be washed into the tails. This leaves the non-magnetics in place to separate normally.
No established mathematical relationship exists for the determination of the smallest size of concentrate particle and the largest size of tailing particle that can be treated together. Other factors, such as character of feed material, shape of particles, difference in specific gravity, slope or grade of table dock and volume of cross flow wash water will alter the final concentrate.
Size of feed material will determine the table settings. Pulverized rod mill pulps for gravity recovery tables should not exceed 65-minus to 100-minus 95% except where specific gravity, size, and shape will allow good recovery. Recovery of precious metals can be made when processing slime size particles down to 500-minus, if the accompanying gangue is not so coarse as to require excessive wash water or excessive grade to remove the gangue, (pronounced gang), to the tails. Wetting agents must be used for settling small micron sized gold particles. Once settled, 400-minus to 500 minus gold particles are readily moved and saved by the RP-4shaker table head motion. Oversized feed material will require excess grade to remove the large sized gangue,thus forcing large pieces of gold further down slope and into the middling. Too much grade and the fine gold will lift off the deck and wash into the tailings. Close screening of the concentrate into several sizes requires less grade to remove the gangue and will produce a cleaner product. A more economical method is to screen the head ore to window screen size (16-minus) or smaller and re-run the middling and cons to recover the larger gold. This concept can be used on the RP-4 shaker tables and will recover all the gold with no extra screens. A general rule for good recovery is less grade for the table deck and as much was water as possible without scouring off the fine gold. Re-processing on two tables will yield a clean concentrate without excess screening. Oversized gold that will not pass through window screen size mounted on RP-4 shaker tables, will be saved in the nugget trap. Bending a small 1/4 screen lip at the discharge end of the screen will trap and save the large gold on the screen for hand removal.
On the first run, at least one inch or more of the black concentrate line should be split out and saved into the #2 concentrate bin. This concentrate will be re-run and the clean gold saved into the #1 concentrate pocket. Argentite silver will be gray to dull black in color and many times this product would be lost in the middling if too close of a split is made.
The riffled portion of the RP-4 shaker table separates coarse non-sized feed material better than the un-riffled cleaning portion. Upon entering the non-riffled cleaning plane, small gangue material will crowd out and force the larger pieces of gold further down slope into the middling. Screen or to classify.
The largest feed particles should not exceed 1/16 in size. It is recommended that a 16-minus or smaller screen be used before concentrating on the RP-4 shaker table, eliminating the need for separate screening devices. Perfect screen sizing of feed material is un-economical, almost impossible, and is not recommended below 65-minus.
A classified feed is recommended for maximum recovery, (dredge concentrates, jig concentrates, etc.) The weight of mill opinion is overwhelmingly in favor of classified feed material for close work. Dredge concentrates are rough classified and limiting the upper size of table feed by means of a submerged deck screen or amechanical classifier is all that is necessary. A separate screen for the sand underflow is used for improved recovery when using tables.
Head feed capacity on the RP-4 tables will differ depending on the feed size, pulp mixture and other conditions. Generally speaking, more head feed material may be processed when feeding unclassified, larger screened sized material and correspondingly, less material may be processed when feeding smaller sized classified rod or ball mill pulps. Smaller classified feed material will yield a cleaner concentrate. Ultimately, the shape of the feed material particles and a quick trial test will determine the maximum upper size.
The width between the riffles of the RP-4 table is small and any particle over 1/8 may cause clogging of the bedding material. A few placer operators will pass 1/8 or larger feed material across the RP-4 table, without a screen, with the intent of making a rough concentrate for final clean up at a later date. This method will work, but excess horizontal slope/grade of the table deck must not be used as some losses of the precious metals will occur. Magnetite black sands feed material, passing a 16-minus screen (window screen size if 16-minus + or -) will separate without losses and make a good concentrate at approximately 500 to 600lbs feed per hour for the RP-4. Head feed material must flow onto the RP-4 screen, at a constant even feed rate. An excess of head feed material placed onthe table and screen at a given time will cause some gold to discharge into the tailings nugget trap. Head feed material should be fed at the end of the water bar into the pre-treatment feed sluice. Do not allow dry head feed material to form thick solids. The wash water will not wash and dilate the head feed material properly, thus allowing fine gold to wash into the tails.
Feed material should disperse quickly and wash down slope at a steady rate, covering all the riffles at the head end,washing and spilling over into the tails trough. A mechanical or wet slurry pump feeder (75% water slurry) is recommended for providing a good steady flow of feed material. This will relieve the mill operator of a tedious chore of a constantly changing concentrate line when hand feeding.
Eight gallons of water per minute is considered minimum for black sands separation/concentration on the RP-4 shaker table. 15 gallons of water per minute is consideredoptimum and will change according to feed material size, feed volume and table grade. A 1 inch hose will pass up to 15 gpm, for good recovery, wash water must completely cover the feed material 1/4 or more on the screen.
The PVC water distribution bar is pre-drilled with individual water volume outlets, supplying a precision water flow. Water volume adjustment can be accomplished by installing a 1 mechanical PVC ball valve for restricting the flow of water to the water distributing holes. Said valve may be attached between the garden hose attachment and water distributing bar.
More water at the head end and less water at the concentrate end is the general rule for precise water flow. More feed material will occupy the head end of the RP-4 shaker table deck in deep troughs and less material will occupy the concentrate end on the cleaning plane. A normal water flow will completely cover the feed material over the entire table and flow with no water turbulence.
A rubber wave cloth is installed to create a water interface and to smooth out all water turbulence. This cloth is installed with holes. Holes allow water to run underneath and over the top of the cloth and upon exiting will create a water interface smoothing out all the water turbulence. Bottom of water cloth must contact the deck.
Avoid excessive slope and shallow turbulent water.For new installations, all horizontal grade/slope adjustments should be calculated measuring from the concentrate end of the steel frame to the mounting base. For fine gold, the deck should be adjusted almost flat.
All head feed must be fed as a 75% water pulp. Clean classified sand size magnetite will feed without too much problem when fed dry. Ground rod or ball mill feed material 65-minus or smaller must be fed wet, (75% water slurry by weight or more) and evenly at a constant rate, spilling over into the tails drain troughat the head end of the table. Feed material without sufficient water will not dilute quickly andwill carry concentrate too far down slope or into the tails. A good wet pulp with a deflocculant and a wetting agent will aid the precious metals to sink and trap within the first riffles, thus moving onto the cleaning plane for film sizing. Round particles of gold will sink instantly and trap within the first riffles. The smaller flat gold particles will be carried further down slope to be trapped in the mid riffles. Potential losses of gold can occur if the table deck is overloaded by force feeding at a faster rate than the smaller flat gold can settle out. Under-feeding will result in the magnetites inability to wash out of the riffles, thus leaving a small amount of magnetiteconcentrated with the gold. A small addition of clean quartz sand added to a black sand concentrate will force the magnetite to the surface and will aid in its removal. Slimes require a separate table operation.
In flotation, surface active substances which have the active constituent in the positive ion. Used to flocculate and to collect minerals that are not flocculated by the reagents, such as oleic acid or soaps, in which the surface active ingredient is the negative ion. Reagents used are chiefly the quaternary ammonium compounds, for example, cetyl trimethyl ammonium bromide.
A substance composed of extremely small particles, ranging from 0.2 micron to 0.005 micron, which when mixed with a liquid will not gravity separate or settle, but remain permanently suspended in solution.
A crusher is a machine designed to reduce large rocks into smaller rocks, gravel, or rock dust. Crushers may be used to reduce the size, or change the form, of waste materials so they can be more easily disposed of or recycled, or to reduce the size of a solid mix of raw materials (as in rock ore), so that pieces of different composition can be differentiated. Crushing is the process of transferring a force amplified by mechanical advantage through a material made of molecules that bond together more strongly, and resist deformation more, than those in the material being crushed do. Crushing devices hold material between two parallel ortangent solid surfaces, and apply sufficient force to bring the surfaces together togenerate enough energy within the material being crushed so that its molecules separate from (fracturing), or change alignment in relation to (deformation), each other. The earliest crushers were hand-held stones, where the weight of the stone provided a boost to muscle power, used against a stone anvil. Querns and mortars are types of these crushing devices.
A basic alkali material, such as sodium carbonate or sodium silicate, used as an electrolyte to disperse and separate non-metallic or metallic particles. Added to Slip to increase fluidity. Used to aid in the beneficiation of ores, to convert into individual very fine particles, creating a state of colloidal suspension in which the individual particles of gold will separate from clay or other particles. This condition being maintained by the attraction of the particles for the dispersing medium, water, purchase at any chemical house.
Manner in which the intensity and direction of an electrical or magnetic field change as a function of time that results from the superposition of two alternating fields, (+/-) that differ in direction and in phase.
The smelting of metallic ores for the recovery of precious metals, requiring a furnace heat. Each milligram of recovered precious metal is gravimetric weighed and reported as one ounce pershort ton. Atomic Absorption (AA finish) is the preferred method for replacing the gravimetric weighing system.
A reagent added to a dispersion of solids in a liquid to bring together the fine particles to form flocs and which thereby promotes settling, especially in clays and soils. For example, lime alters the soil pH and acts as a flocculent in clay soils. Acid reagents and brine are also used as a flocculent.
The method of mineral separation in which a froth created in water with air and by a variety of reagents floats some finely crushed minerals, whereas other minerals sink. Separate concentrates are made possible by the use of suitable depressors and activators.
An igneous oxide of iron, with a specific gravity of 5.2 and having an iron content of 65-70% or more. Limonite crystals, sometimes mistaken for magnetite, occurs with the magnetite and sometimes may contain gold. Vinegar will remove gold locked in limonite coated magnetite.
In materials processing a grinder is a machine for producing fine particle size reduction through attrition and compressive forces at the grain size level. See also CRUSHER for mechanisms producing larger particles. Since the grinding process needs generally a lot of energy, an original experimental way to measure the energy used locally during milling with different machines was proposed recently.
A typical type of fine grinder is the ball mill. A slightly inclined or horizontal rotating cylinder is partially filled with balls, usually stone or metal, which grinds material to the necessary fineness by friction and impact with the tumbling balls. Ball mills normally operate with an approximate ball charge of 30%. Ball mills are characterized by their smaller (comparatively) diameter and longer length, and often have a length 1.5 to 2.5 times the diameter. The feed is at one end of the cylinder and the discharge is at the other. Ball mills are commonly used in the manufacture of Portland cement and finer grinding stages of mineral processing. Industrial ball mills can be as large as 8.5 m (28 ft) in diameter with a 22 MW motor, drawing approximately 0.0011% of the total worlds power. However, small versions of ball mills can be found in laboratories where they are used for grinding sample material for quality assurance.
A rotating drum causes friction and attrition between steel rods and ore particles. But note that the term rod mill is also used as a synonym for a slitting mill, which makes rods of iron or other metal. Rod mills are less common than ball mills for grinding minerals.
Screening is the separation of solid materials of different sizes by causing one component to remain on a surface provided with apertures through which the other component passes. Screen size is determined by the number of openings per running inch. Wire size will affect size of openings. -500=500 openings per inch is maximum for gravity operations due to having a solid disperse phase.
Long established in concentration of sands or finely crushed ores by gravity. Plane, rhombohedra deck is mounted horizontally and can be sloped about its axis by a tilting screw. Deck is molded of ABS plastic, and has longitudinal riffles dying a discharge end to a smooth cleaning area. An eccentric is used to create a gentle forward motion, compounded to full speed and a rapid return motion of table longitudinally. This instant reverse motion moves the sands along, while they are exposed to the sweeping and scouring action of a film of water flowingdown slope into a launder trough and concentrates are moved along to be discharged at the opposite end of the deck.
A material of extremely fine particle size encountered in ore treatment, containing valuable ore in particles so fine, as to be carried in suspension by water. De-slime in hydrocyclones before concentrating for maximum recovery of precious metals.
A mixture of finely divided, micron/colloidal particles in a liquid. The particles are so small that they do not settle, but are kept in suspension by the motion of molecules of the liquid. Not amenable to gravity separation. (Bureau of Mines)
Flotation process practiced on a shaking table. Pulverized ore is de-slimed, conditioned with flotation reagents and fed to table as a slurry. Air is introduced into the water system and floatable particles become glom rules, held together by minute air bubbles and positive charged edge adhesion. Generated froth can be discharged into the tailings launder trough or concentrates.
The parts, or a part of any incoherent or fluid material separated as refuse, or separately treated as inferior in quality or value. The gangue or valueless refuse material resulting from the washing, concentration or treatment of pulverized head ore. Tailings from metalliferous mines will appear as sandy soil and will contain no large rock, not to be confused with dumps.
A substance that lowers the surface tension of water and thus enables it to mix more readily with head ore. Foreign substances, such as natural occurring pine oils, vegetation oils and mill grease prevent surface wetting and cause gold to float. Addition agents, such as detergents, (dawn), wetting out is a preliminary step in deflocculating for retarding gold losses.
RP4 shaker table for sale mini gold shaker table RP4 shaker table instructions RP4 shaker table dimensions RP4 gold shaker table RP 4 gravity shaker table utech RP4 shaker table RP 4 gravity shaker table price used RP4 shaker table for sale
Global mining solutions warrants that all mining equipment manufactured will be as specified and will be free from defects in material and workmanship for a period of one year for the RP-4. Providing that the buyer heeds the cautions listed herein and does not alter, modify or disassemble the product, gms liability under this warranty shall be limited to the repair or replacement upon return to gms if found to be defective at any time during the warranty. In no event shall the warranty extend later than the date specified in the warranty from the date of shipment of product by GMS. Repair or replacement, less freight, shall be made by gms at the factory in Prineville, Oregon, USA.
All bearings are sealed and no grease maintenance is required. Do not use paint thinners, or ketones to clean your deck. A small amount of grease should be applied to the adjustable handle which is used for the changing the slope of the deck.
Do not allow the RP-4 to stand in direct sunlight without water. Always keep covered and out of the sun when not in use. Heat may cause the deck to warp. Do not lift or pull on the abs plastic top, always lift using the steel frame. Do not attach anything to the abs plastic top. Do not attach PVC pipe to concentrate discharge tubes, constant vibration from the excess weight will cause stress failure of the plastic.
Considering the increasing applications of micropile systems in seismically active areas, a better understanding of their seismic performance and the key controlling factors is of high significance. This paper presents experimental investigations of the seismic performance of a small-scale physical model of micropiles under seismic ground motions. Shaking table tests were performed on a 44 group of vertical micropiles embedded in loose sand. Horizontal acceleration time histories recorded from the 1940 El Centro earthquake and 1995 Kobe earthquake were applied to the base of the soil container. The response of the physical model was monitored in terms of horizontal accelerations at different levels and bending moments induced in the micropiles. The experimental results indicate that in all shaking events, the magnitudes of horizontal accelerations on the soil surface and the pile cap were amplified with respect to the input motion. Bending moments were induced in the micropiles and peaked at the mid-depth. It was also found that inclining the micropiles led to improvement in their seismic performance, reducing both the acceleration response on soil surface and pile cap, and the induced bending moments in the micropiles. Finite element simulations of shaking table tests have been performed, and the results are in reasonable agreement with observations from the experiments.
Alnuaim AM, El Naggar MH, El Naggar H (2015) Performance of micropiled raft in clay subjected to vertical concentrated load: centrifuge modeling. Can Geotech J 52(12):20172029. https://doi.org/10.1139/cgj-2014-0448
Bardet JP, Idriss IM, ORourke, Adachi N, Hamada M, Ishihara K (1996) North AmericaJapan workshop on the geotechnical aspects of the Kobe, Loma Prieta, and Northridge earthquake. Report No. 98-36 to National science foundation, air force office of scientific research and Japanese Geotechnical Society, Osaka, Japan
Benslimane A, Juran A, Hanna A, Drabkin S, Perlo S, Frank R (1998) Seismic retrofitting using micropile systems: centrifugal model studies. In: Proceedings of 4th international conference on case histories in geotechnical engineering, St. Louis, Missouri, pp 12601268
Brachman RWI, LeBlanc JM (2017) Short-term lateral response of a buried modular polymer stormwater collection structure to compaction and overburden pressure. J Geotech Geoenviron Eng 143(9):04017070. https://doi.org/10.1061/(ASCE)GT.1943-5606.0001762
Brachman RWI, Moore ID, Rowe RK (2000) The design of a laboratory facility for evaluating the structural response of small-diameter buried pipes. Can Geotech J 37(2):281295. https://doi.org/10.1139/t99-104
Chau KT, Shen CY, Guo X (2008) Nonlinear seismic soilpilestructure interactions: shaking table tests and FEM analyses. Soil Dyn Earthq Eng 29(2):300310. https://doi.org/10.1016/j.soildyn.2008.02.004
Ghorbani A, Hasanzadehshooiili H, Ghamari E (2014) Comprehensive three-dimensional finite element analysis, parametric study and sensitivity analysis on the seismic performance of soilmicropile-superstructure interaction. Soil Dyn Earthq Eng 58:2136. https://doi.org/10.1016/j.soildyn.2013.12.001
Giannakou A, Gerolymos N, Gazetas G, Tazoh T, Anastasopoulos I (2010) Seismic behavior of batter piles: elastic response. J Geotech Geoenviron Eng 136(9):11871199. https://doi.org/10.1061/(ASCE)GT.1943-5606.0000337
Itani M, Kawamura T, Onodera S, Oshita T (2000) Centrifugal model test on pile group effect of pile foundation reinforced by micropile. In: Proceedings of the 3rd international workshop on micropiles, Turku, Finland
Joshi P, Brachman RWI, Rowe RK (2017) Hydraulic performance of GCL seams without field-applied supplemental bentonite below a geomembrane wrinkle. J Geotech Geoenviron Eng 143(9):04017068. https://doi.org/10.1061/(ASCE)GT.1943-5606.0001756
Kampitsis AE, Sapountzakis EJ, Giannakos SK, Gerolymos NA (2013) Seismic soilpilestructure kinematic and inertial interactionA new beam approach. Soil Dyn Earthq Eng 55:211224. https://doi.org/10.1016/j.soildyn.2013.09.023
Komakpanah A, Jalilian Mashhoud H, Yin JH, Leung AYF (2017) Shaking table investigation of effect of inclination angle on seismic performance of micropiles. Int J Geomech. https://doi.org/10.1061/(ASCE)GM.1943-5622.0001236
Medina C, Padron LA, Maeso AZ (2015) Influence of pile inclination angle on the dynamic properties and seismic response of piled structures. Soil Dyn Earthq Eng 69:196206. https://doi.org/10.1016/j.soildyn.2014.10.027
Ni P, Mei G, Zhao Y (2017) Displacement-dependent earth pressures on rigid retaining walls with compressible geofoam inclusions: physical modeling and analytical solutions. Int J Geomech 17(6):04016132. https://doi.org/10.1061/(ASCE)GM.1943-5622.0000838
Ousta R, Shahrour I (2001) Three-dimensional analysis of the seismic behaviour of micropiles used in the reinforcement of saturated soil. Int J Numer Anal Methods Geomech 1(25):183196. https://doi.org/10.1002/nag.124
Shahrour I, Sadek M, Ousta R (2001) Seismic behavior of micropiles used as foundation support elements: three-dimensional finite element analysis. J Transp Res Board 1772:8490. https://doi.org/10.3141/1772-10
Sheikh MN, Tsang H, Yaghmaei-Sabegh S, Anbazhagan P (2013) Evaluation of damping modification factors for seismic response spectra. In: Anderson S (ed) Australian earthquake engineering society conference 2013. Australian Earthquake Engineering Society, Tasmania, pp 113
Tazoh T, Sato M, Jang J, Taji Y, Gazetas G, Anastopoulos I (2010) Kinematic response of batter pile foundation: centrifuge tests. In: Orense et al. (eds) Soil-foundation-structure interaction. CRC Press, Boca Raton
Yin JH, Komakpanah A, Jalilian Mashhoud H, Leung AYF (2017) Shaking table test study of dynamic behavior of micropiles in loose sand. Soil Dyn Earthq Eng 110:5369. https://doi.org/10.1016/j.soildyn.2018.03.008
This research project was financially supported by a research grant from Collaborative Research Fund (CRF) Project No. PolyU12/CRF/13E from the Research Grants Council (RGC) of the Government of Hong Kong Special Administrative Region of China, and a research grant (Project No. 2014CB047001) from Ministry of Science and Technology of the Peoples Republic of China. The authors wish to acknowledge the help of technical staff at laboratories of Structural Dynamics, Concrete Technology, Soil Mechanics, and Rock Mechanics in The Hong Kong Polytechnic University.
Jalilian Mashhoud, H., Yin, JH., Komak Panah, A. et al. A 1-g shaking table investigation on response of a micropile system to earthquake excitation. Acta Geotech. 15, 827846 (2020). https://doi.org/10.1007/s11440-018-0742-6
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Zuo-ju Wu, Zhi-jia Wang, Jun-wei Bi, Xiao Fu, Yong Yao, "Shaking Table Test on the Seismic Responses of a Slope Reinforced by Prestressed Anchor Cables and Double-Row Antisliding Piles", Shock and Vibration, vol. 2021, Article ID 9952380, 13 pages, 2021. https://doi.org/10.1155/2021/9952380
The combined retaining structure has gradually received considerable attention in the slope engineering, due to its good reinforcement effects. However, most of the published research studies were focused on the seismic responses of the single-formal supporting structure only. The investigations of dynamic responses of the combined retaining structures are scarce, and the current seismic design is conducted mainly based on experiences. In this work, a series of large-scale shaking table tests were conducted to investigate the seismic responses of the combined retaining structures (i.e., prestressed anchor cables and double-row antisliding piles) and the reinforced slope under seismic excitations, including amplification effect of internal and surface acceleration of the reinforced slope, distribution and change of prestress of the anchor cable, dynamic response of soil pressure behind the antislide pile, and horizontal displacement of the reinforced slope surface. Test results show that, supported by the reinforcement of composite support system, the slope with the multilayer weak sliding surface can experience strong ground motion of 0.9g. The load of the antisliding pile has reached 80% of its bearing capacity, and the load of the anchor cable has reached 75.0% of its bearing capacity. When the seismic intensity reaches 0.5g, the slope surface has an obvious downward trend, which will make the corresponding soil pressure suddenly increase after the antislide pile. At the potential sliding zone, the axial force of the anchor cable will increase suddenly under the action of earthquake; after the earthquake, the initial prestress of the anchor cable will be lost, with the loss range of 17.0%23.0%. These test results would provide an important reference for the further study of the seismic performance of such composite support structure.
There are many mountains in Southwest China, so there are many slopes. Particularly, most slope projects in Sichuan Province are located in the areas with high seismic intensity. When strong earthquakes occur, these supporting structures (such as anchor cables and antisliding piles) are often damaged . Therefore, the seismic research of the slope-supporting structure is of great significance.
As an important mean to study the seismic performance of supporting structures, the shaking table test has been developing rapidly in the past decade. Lai et al.  conducted shaking table tests to research the seismic responses of a slope reinforced by double-row antisliding piles, which indicates that the double-row antisliding piles could effectively resist the combination of tension and shear during earthquake. Jiang et al.  performed a series of shaking table model tests of the slope supported by anchor cables to deeply study the responses and characteristics of the reinforced slope under earthquake action. Ye et al.  investigated the seismic behavior of a slope reinforced by prestressed anchor cables through the shaking table test, in which the antislip mechanism of the prestressed anchor cables is well analyzed. Lin et al.  conducted experimental and numerical investigations and researched the seismic behavior of an anchoring frame beam under earthquakes. Through model tests, Zheng et al.  investigated the seismic-induced damage and deformation patterns of a rock slope reinforced by prestressed cables. Xu et al.  conducted a shaking table test to determine the load transfer mechanism and dynamic response characteristics of a slope supported by adaptive anchor cables. Ma et al.  used the shaking table test to study the distribution and variation of the dynamic soil pressures acting on supporting structures, including the antisliding pile and the prestressed anchor slab-pile wall. Through a series of shaking table tests, Ding et al.  investigated the seismic behavior and performance of the slopes reinforced by concrete-canvas and composite reinforcement. Zhou et al.  analyzed the seismic damages of road slopes in Wenchuan earthquake and pointed out that the prestressed anchor cable and antisliding pile have good earthquake resistance performance. Currently, the combined retaining structures are more and more widely applied, especially for large-scale slope and landslide projects. Lin et al.  performed shaking table tests and investigated the dynamic responses of a slope which is reinforced by prestressed anchor cables and single-row antisliding piles. More recently, Fan et al.  conducted experimental investigations to study the dynamic behavior of a slope reinforced by double-row antisliding piles and prestressed anchor cables under Wenchuan seismic excitations.
The above studies mainly focus on the seismic response of the single-formal support structure. However, the dynamic response of the slope reinforced by the composite support structure under earthquake action is very limited. Moreover, investigations related to the seismic responses of the slope reinforced by prestressed anchor cables and double-row antisliding piles are rather scarce, and the corresponding design method for such combined retaining structure is still unclear. Therefore, further in-depth study on the dynamic responses of prestressed anchor cables and double-row antisliding piles under the earthquake loadings must be available to improve the current seismic design.
To address these issues, a series of large-scale shaking table tests were conducted to investigate the seismic responses of a slope reinforced by prestressed anchor cables and double-row antisliding piles. Some meaningful conclusions and recommendations are obtained based on the analysis of test results.
Figure 1 shows the prototype slope that is located in Sichuan, China. The height and width of the slope are about 150.00m and 325.00m, respectively, and the elevation of the slope toe is 606.00m. A typical cross section for the shaking table test is selected, as shown in Figure 2. According to the site exploration, the slip bed of the prototype slope mainly formed in intact celadon shale, and the sliding mass mainly consists of the highly weathered shale and Quaternary alluvial deposit. There are two slip surfaces inside the slope, which the potential sliding zones consist of the silty clay with minor gravels. The parameters of the prototype slope are listed in Table 1. In reference to Seismic Ground Motion Parameters Zonation Map of China , the seismic design intensity of the prototype site is 7.00. Therefore, taking consideration of the significance of the prototype slope, the effects of seismic loadings should not be neglected. According to the results of stability analyses, the safety factor of the prototype slope under earthquakes is 1.03, and the value of which under the pseudostatic conditions is 0.90. The peak ground acceleration and seismic influence coefficient in the horizontal direction are 0.15g and 0.24, respectively. The calculations show that the residual sliding force of prototype slopes is extremely large; thus, the original design of single-row antisliding piles and prestressed anchor cables could not meet the needs of stability. Therefore, the slope is designed to be reinforced by prestressed anchor cables and double-row antisliding piles.
The shaking table facility used for the tests allows input of three directions of earthquake records with independent control. The shaking table has 6 degrees of freedom, including 3 degrees of translation and 3 degrees of rotation, and the dimensions of which are 6.0m by 6.0m. At full load, the maximum acceleration could reach 1.0g in the horizontal direction and 0.8g in the vertical direction. The maximum displacements of the shaking table in the horizontal and vertical direction are 150.0mm and 100.0mm, respectively, and the loading frequency range of which is 0.1Hz80.0Hz. Additionally, a data acquisition system with 128 channels is adopted, which the maximum error can be controlled within 5.0%.
According to the scaling laws, three controlling parameters were selected, which are the dimension L, density , and acceleration a, respectively. Limited by the dimensions and bearing capacity of the shaking table facility, the similar constants of dimension (CL), density (C), and acceleration (Ca) were set to be CL=100.0, C=1.0, and Ca=1.0 for this shaking table test, leading to the model slope height of 200.0cm. Based on the Buckingham theorem , the similarity ratios of other parameters for this model test could be obtained, as illustrated in Table 2, and the detailed derivation of which could be found in Ref. .
The slope model was placed in a rigid box container with waterproof treatment which fixed on the shaking table, and the dimensions of the box are 325.0cm150.0cm250.0cm (lengthwidthheight), as shown in Figure 3. The slope model was built layer by layer, in which the height of each layer is 20.0cm. Based on the required thickness and density of each layer, similar materials with a certain quality would be placed into the model box and then compacted to the desired thickness. After each layer was compacted, the cutting ring method was applied to ensure whether the unit weight meets the requirements or not. For the potential sliding zones, the similar materials were obtained from the prototype slope and remodeled for the shaking table tests. After the test model was built, the slope model is saturated through the pipes preinstalled in the model slope. Additionally, for each component of the model slope, samples were collected, and soil mechanics tests (i.e., cutting ring method, resonant column test, direct shear test, uniaxial compression test, and triaxial test) were performed to obtain the physical parameters. The mechanical parameters of the test model are presented in Table 3.
After the model slope was completed, the prestressed anchor cables and double-row antisliding piles were used to reinforce the slope through the reserved holes. Considered to be rigid, the antisliding piles were made of concrete with a section of 2.0cm by 3.0cm, and the bending deformation of which were ignored in this work. As shown in Figure 4, a row of antisliding piles labeled the Pile A were installed at the waist of the model slope, and the other row of piles named the Pile B were located at the slope toe. The height of the Pile A and B are 20.0cm and 16.0cm, respectively. Due to the limitation of the model size, it is difficult to install too many rows of prestressed anchor cables in the mode slope. It should be pointed out, in this work, the adjacent six rows of prestressed anchor cables are merged to be one row. Therefore, three rows of prestressed anchor cables numbered 1#, 2#, and 3# were installed above the Pile A, as can be seen in Figure 4; the other four rows were installed between the Pile A and B, which were numbered with 4#, 5#, 6#, and 7#.
For the prestressed anchor cables, as presented in Figure 5(a), the construction holes were reserved using PVC pipes with diameter of 8.0cm. The prefabricated anchor cables were inserted into the reserved holes. Then, with pulling the PVC pipes out, the reserved holes were filled with sand simultaneously. The depth of sand was determined by the designed length of the anchorage segment of the anchor cable. In this shaking table test, the length of the anchorage segment is 8.0cm. The cable material is steel with the diameter of 2.0cm. The inclined angle of the prestressed anchor cable is set to 20.0. According to the designed pulling resistance and the similarity ratio, the filled sand in reserved holes was manually compacted for a given number of times, which was determined by the previous compaction test in the laboratory, as presented in Figure 5(d). The prestress of the anchor cable was applied by rotating the nut on the screw which was fixed on the lattice beam, and the applied prestress was close to real-time values measured by the axial force monitoring. It should be noted that utilizing the sand to fill the reserved holes does not seem to match the in situ field situation. However, by controlling and monitoring the prestress strictly, the specific physical significance of anchor cables in this shaking table test agrees well with that in the in situ field situation. In addition, to attenuate the wave reflection from the steel box during shaking, the expanded polystyrene boards with a thickness of 10.0cm were placed between the slope model and test box [18, 19].
As shown in Figure 4, a total of 14 three-dimensional accelerometers were installed inside the model slope and on the slope surface to measure accelerations in the horizontal and vertical directions. For the horizontal direction, the sensitivity of accelerometers is 173.46mv/g, which is 192.08mv/g in the vertical direction. To measure the displacements on the slope surface, six laser displacement meters with the range of 30.00cm were installed at different locations throughout the slope height, and the sensitivity of which was 33.33mv/mm. For the prestressed anchor cables, as shown in Figure 5(b), axial force sensors installed at the tension segment were employed to measure the axial force. The sensitivity of the axial force sensor was 1.50mv/v. Additionally, the dynamic earth pressure acting on the back of antisliding piles was measured by the earth pressure cells with the measuring range of 0.00MPa0.80MPa. As illustrated in Figure 5(c), five earth pressure cells were installed on the Pile B and numbered with 1#5#; the other five ones for the Pile A were numbered with 6#10#.
All the abovementioned sensors are new, and calibration of which was conducted before the shaking table test. Moreover, to attenuate the boundary effect on the test results, all the earth pressure cells and axial force sensors were installed on the middle column of antisliding piles and prestressed anchor cables, and all the accelerometers and laser displacement meters were also installed in the middle section.
The seismic loading used in this shaking table test was the El Centro earthquake record which has been widely used in the earthquake engineering. Two simultaneous loading directions of seismic excitations were applied in this shaking table test, namely, the X and Z direction, for which the corresponding time histories of the input seismic motions can be seen in Figure 6. Based on the similarity criteria, the input earthquake records were compressed in the time axis with a compression ratio of 10.00 (the similarity ratio of Time t). Six different horizontal peak accelerations of the input seismic loadings (i.e., 0.15g, 0.30g, 0.40g, 0.50g, 0.70g, and 0.90g) were selected. As highlighted in Refs. , the vertical peak acceleration is generally two-thirds of the horizontal peak acceleration. Additionally, before the excitation of the El Centro earthquake record, the model was scanned by the 0.05g white noise. The loading sequence of the shaking table tests is listed in Table 4.
The slope would have obvious nonlinear responses under strong seismic motions . According to Ref. , the acceleration amplification behavior of the prototype slope could be well revealed by the shaking table test. In this study, the baseline corrected and band-pass filtered are adopted to the measured signals before calculating amplification factors. The peak values of horizontal accelerations are obtained by taking the maximum absolute values from the acceleration time histories.
In this section, the ratio of the peak horizontal acceleration obtained on the slope surface or inside the slope to that collected by A14 is defined as the amplification factor. Figure 7 presents the variations of the amplification factor of horizontal acceleration on the slope surface and inside the slope. As shown in Figure 7(a), comparing with the slope mass above the Pile A, the amplification factors on the slope surface between the Pile A and B are smaller. This indicates that the existence of the Pile A weakens the seismic responses of the slope effectively. However, for the slope mass above 1# anchor cable, the acceleration amplification factor increases rapidly along the slope height because of the reason that this part of the slope is not reinforced by any supporting structures. Based on the above analysis, the prestressed anchor cables and double-row antisliding piles could effectively reduce the dynamic responses of the slope surface under earthquakes. It can be seen from Figure 7(b) that the amplification factor of horizontal acceleration inside the slope increases generally with the slope height, whereas the acceleration amplification factor decreases when the seismic waves pass through the potential sliding zone from the bottom to the top. It indicates that some of the energy carried by earthquake waves could be dissipated by the potential sliding zone.
To research the seismic responses of prestressed anchor cables, the axial force of each anchor cable was measured, and the initial values of which before each excitation are listed in Table 5. For 2# prestressed anchor cable, the time histories of the axial force under the El Centro seismic loading with different amplitudes are plotted in Figure 8. From the figure, the variations of axial forces are similar to the time history of the input excitation (in Figure 6). The peak values of axial force occur at around the same time for that of the input earthquake motion. In this work, to well discuss the seismic responses of the prestressed anchor cables, the peak values and residual values of the axial force are analyzed separately.
Figure 9 shows that the peak values of the axial force of prestressed anchor cables increase with the amplitudes of the input seismic loadings, especially when the input amplitude is larger than 0.5g. It indicates that the performance of the anchor cable is taken full advantage when the amplitude of excitation is greater than 0.5g. As presented in Figure 4, seven rows of prestressed anchor cables can be divided into two parts by the Pile A. The maximum increment of the axial force occurs in 2# prestressed anchor cable. The increment of the peak axial force of 1# anchor cable is larger than that of 3# anchor cable, especially when the input amplitude of seismic motion is larger than 0.4g. It indicates that stronger dynamic responses occur on the upper part of the slope. Under earthquake loadings, the sliding force is firstly undertaken by the anchor cables located in the upper part of the slope, and the rest of which is undertaken by other anchor cables. For the prestressed anchor cables located between the Pile A and B, the increment of the peak axial force increases generally with the slope height. However, the increment of the peak axial force in 7# anchor cable is larger than 5# and 6# anchor cables and smaller than 4# anchor cable. This is due to that, with a shorter free segment, the seismic responses of the axial force of 7# anchor cable are mainly influenced by the anchor cable length.
To further reveal the relationship between the initial axial force and the variation of axial force during shaking, the notation is defined in this section as the increase rate of axial force, which is expressed as follows:where A1 is the initial axial force of the anchor cable and A2 denotes the peak value of axial force during earthquake loadings.
The increase rates of the axial force of anchor cables under the El Centro earthquake motions with different amplitudes are depicted in Figure 10. It can be seen from the figure that, under 0.50g, 0.70g, and 0.90g seismic excitations, the increase rates of axial force for 2# anchor cable are 2.49, 4.22, and 6.79, respectively, which is the maximum among the prestressed anchor cables. For the other anchor cables, the increase rates are smaller than 2.00 when the amplitude of earthquake loading is not larger than 0.70g, and in the range of 0.833.30 under 0.90g seismic motions. In reference to the current seismic design method, the safety factor of the calculation of the section area for the prestressed anchor cable is 2.20, in which only static condition is considered. It can be highlighted that the performance of the prestressed anchor cable under dynamic conditions should be taken into consideration in the seismic design.
The occurrence time of the peak axial force for seven prestressed anchor cables under different excitations is shown in Figure 11. To ensure the integrity of the data collected in the shaking table tests, the data acquisition starts some time before the input of each excitation. Therefore, it is meaningless to compare the occurrence time of the peak axial force with time history of the input El Centro seismic motion, and the comparison of the occurrence time of peak axial force between different prestressed anchor cables would be discussed in this work. It can be seen from Figure 11 that the most anchor cables get their peak vibration values almost at the same time under each seismic excitation, which indicates that all the prestressed anchor cables work together during shaking. However, under 0.15g earthquake motion, the occurrence time of the peak axial force for the anchor cables located in the upper part of the slope is somewhat earlier than those in the lower part. This is mainly because that the slope mass is compacted during the seismic excitations, which affects the propagation of the earthquake wave in the slope.
For the seismic design of the prestressed anchor cable, the prestress loss and the residual value of axial force after earthquake are of great significance. In this work, the notation is defined as the changing rate of axial force, which is expressed asin which A1 is the initial axial force of the anchor cable and A3 denotes the residual value of axial force after each seismic excitation.
The changing rates of axial force for each anchor cable under seismic excitations are presented in Figure 12. When subjected to 0.15g seismic motions, the loss of prestress for 1#, 2#, and 3# anchor cables are 11.00%, 16.00%, and 22.00%, respectively. Under the excitations with amplitudes in the range of 0.30g0.70g, the prestress of 1# anchor cable is lost by 4.00% approximately, and by 21.00% under 0.90g seismic motion. Both for 2# and 3# anchor cables, the prestress increases under 0.30g0.90g seismic excitations. The maximum increment of prestress in 2# anchor cable is about 10.00%, which is greater than that in 3# anchor cable. The loss of prestress for 4#, 5#, and 6# anchor cables are 21.00%, 23.00%, and 19.00% under 0.15g earthquake excitation, whereas there is almost no prestress loss in 7# anchor cable. When subjected to 0.30g excitation, the residual axial forces of prestressed anchor cables between the Pile A and B are mainly identical with the initial values. In addition, under the seismic motions with other amplitudes, the prestress of these four anchor cables increases about 10.00%. According to the analysis above, since the maximum of prestress loss is about 23.00% in this test, it is suggested that the initial axial force of the prestressed anchor cable could be raised by 1.201.30 times in the seismic design.
The test results show that the axial forces of the prestressed anchor cables in different slope areas are significantly different. It indicates that, for the current seismic design method, all the prestressed anchor cables are assumed to sustain the same load is inaccurate and uneconomic. In practice, the failure of one anchor cable can cause the failures of adjacent ones because of the chain reaction, which could lead to the slope failure. Therefore, the seismic response differences between anchor cables located in different areas should be fully taken into consideration in the seismic design. Additionally, to ensure the reliability of the prestressed anchor cables and the slope stability, specific design considerations should be adopted in the areas with different geological conditions.
The lateral earth pressures acting on the back of the antisliding Pile A and B under the excitations of El Centro earthquakes are shown in Figure 13. It should be noted that the lateral earth pressure plotted in Figure 13 is the dynamic earth, and the static pressure is not considered in this section. Both for the Pile A and B, the lateral earth pressure increases with the increasing input amplitude. Comparing with the Pile A, the lateral earth pressure acting on the back of the Pile B is much greater, especially for the location with relative height of 0.17 and 0.50. Under the excitations with the amplitude of 0.15g and 0.30g, the distribution curves of earth pressure acting on the Pile A are similar to the Pile B. However, when the input amplitude becomes larger than 0.50g, the lateral earth pressure acting on the Pile A decreases first and then increases along the height, and the minimum of which occurs near the location with relative height of 0.67. It can be seen from Figure 14(b), for the Pile A, the earth pressure acting on the pile toe is larger than that acting on the pile top. As highlighted in Reference , the earth pressure measured behind the piles can be equivalent to the earth pressure used in the traditional pseudostatic design, due to the piles are assumed to be rigid. Hence, the major cause of this phenomenon is that the plastic strain happens in the surrounding soil near the top and toe of the pile under strong earthquake motions. Note that, comparing with the soils, the model piles in this test are of infinite strength and stiffness, leading to rigid rotation and translation of piles during seismic loading. In addition, the difference of the distribution of earth pressure between the Pile A and B is mainly contributed that the Pile B is embedded much deeper than the Pile A and behaving nearly as a fixed pile.
For the seismic responses of double-row antisliding piles, few studies were related to the load-sharing ratio. The ratios between the peak lateral earth pressure acting on the back of the Pile B and A are depicted in Figure 14. It can be seen from the figure that the ratios change mainly in the range of 2.05.0, implying that there is a large difference on the load-sharing ratios between the Pile A and B. The earth pressure acting on the back of the Pile B is much larger than that of the Pile A. As highlighted in Refs. [15, 26], the seismic design intensity scale of most areas in China is not larger than 9.0, and the corresponding design acceleration of which is smaller than 0.4g. The test results in this work have an important practical significance for China and also can provide a reference for other countries and regions in the world.
The horizontal displacements on the slope surface were measured by the laser displacement meters located at different locations throughout the slope height. In this work, the horizontal displacement towards the slope is defined as negative and that away from the slope is defined as positive. In Figure 15, the peak horizontal displacements during seismic excitations and the postearthquake permanent displacements are presented. The figure shows that, when the input amplitude is not larger than 0.50g, the permanent lateral displacements on the slope surface are small which indicates that the reinforced slope is of good overall stability. The peak displacement and permanent displacement on the slope surface increase with the increasing amplitude of the input seismic motions. The slope could be divided into two parts by the Pile A, and the horizontal displacements on the slope surface both for the upper and lower parts of the slope increase with the elevation. Additionally, it should be noted that the negative permanent displacements on the slope surface occur under 0.15g El Centro earthquake motion. It is mainly because of that the slope mass is compacted somewhat under the dual actions of seismic motion and retaining structures, and this phenomenon is in accordance with the prestress loss of anchor cables under 0.15g seismic motion.
According to the test results, several conclusions can be drawn:(1)Comparing with the unreinforced part of the slope, the value and the increase rate of the acceleration amplification factor can be effectively controlled by the reinforcements of prestressed anchor cables and double-row antisliding piles, especially for the slope mass between the Pile A and B.(2)The maximum of prestress loss is 23.00%. When subjected 0.30g0.90g excitations, the maximum increment of axial force is 15.00%. It can be highlighted that the initial prestress of the anchor cable is suggested to be raised by 1.201.30 times in the seismic design for the slope with high requirements of deformation control.(3)The lateral earth pressures acting on the back of the Pile A and B increase with the increasing amplitude of the input seismic motions. Comparing with the Pile B located at the slope toe, the earthquake loading undertaken by the Pile A located at the slope waist is obviously smaller, and the load-sharing ratios between the Pile A and B mainly changed in the range of 2.05.0.(4)Under the seismic excitations, especially the input amplitude not larger than 0.5g, the lateral displacements on the slope surface can be controlled by the combined retaining structures well. It can be concluded that, reinforced by prestressed anchor cables and double-row antisliding piles, the slope would have a good overall stability.
This work was supported by the National Natural Science Foundation of China (Grant no. 51808466) and Young Talents Science and Technology Innovation Project of Hainan Association for Science and Technology (QCXM201807).
Copyright 2021 Zuo-ju Wu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Inclined pile foundations are widely used in civil engineering by virtue of sufficient horizontal stiffness, but few studies have touched upon the seismic performance of inclined piles in liquefiable soil. To better understand the performance of the inclined piles in liquefiable soil under earthquake conditions, a series of 1g shaking table tests of inclined and vertical piles in liquefiable soil were performed. Superstructure-pile-soil dynamic interaction was considered while three types of earthquake waves with different characteristics were selected as the applied earthquake motions. The horizontal acceleration of the superstructure and the pile cap, the rotational acceleration of the pile cap, the total base shear force, and the bending moment of two types of physical models were monitored and analyzed. The results show that inclined piles in liquefiable soil can effectively reduce the horizontal vibration of the superstructure and the pile cap, and the acceleration reduction of the pile cap is about 2.5 times larger than that of the superstructure. Meanwhile, inclined piles can also reduce the total base shear force, and the extent of reduction depends on the input earthquake wave. Besides, the results suggest that the maximum bending moment of inclined piles is located at the pile head, and its value is positively correlated with the amplitude of the earthquake wave, and is affected by the type of the input earthquake wave. Overall, inclined pile foundations show satisfactory seismic performance for a superstructure-foundation-liquefiable soil system, and this study, with a rich amount of data, can serve as an important reference for the seismic design of inclined piles in liquefiable soil.
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Gerolymos N, Giannakou A, Anastasopoulos I, Gazetas G (2008) Evidence of beneficial role of inclined piles: observations and summary of numerical analyses. Bull Earthq Eng 6:705722. https://doi.org/10.1007/s10518-008-9085-2
Giannakou A, Gerolymos N, Gazetas G, Tazoh T, Anastasopoulos I (2010) Seismic behavior of batter piles: elastic response. J Geotech Geoenviron Eng 136:11871199. https://doi.org/10.1061/(ASCE)GT.1943-5606.0000337
Harn RE (2004) Have batter piles gotten a bad rap in seismic zones (or everything you wanted to know about batter piles but were afraid to ask). In: Ports 2004: port development in the changing world, pp 110. https://doi.org/10.1061/40727(2004)13
Ling XZ, Wang C, Wang C (2004) Scaling modeling method of shaking table test of dynamic interaction of pile-soil-bridge structure in ground of soil liquefaction. Chin J Rock Mech Eng 23:450456. https://doi.org/10.3321/j.issn:1000-6915.2004.03.017
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The research was supported by the National Key R & D Program of China (Grant no. 2016YFC0802203) and Science and Technology Research and Development Program of China Railway Corporation (Grant no. 2013G001-A-2).
Chen, W., Ma, J., Cao, S. et al. Shaking table test study on seismic performance of inclined pile foundations in liquefiable soil. Environ Earth Sci 79, 398 (2020). https://doi.org/10.1007/s12665-020-09139-4
Want to know one of the sexiest cues of all? The seated parallel legs cue. This is when a woman crosses her legs and relaxes one leg on top of the other, highlighting that calf muscle and giving the appearance of higher muscle tone. Alternatively, the legs might be placed to one side and uncrossed.
In the movie, The Wolf of Wall Street, Jordan Belfort and Donnie Azoff can be seen spreading their legs wide as they slouch on the couch. What does this cue mean?a) Angerb) Dominancec) Stressd) Interest
Theres also a reason behind all the spreadingThe Economonitor reported that the average male has shoulders 28% wider than his hips, while women have shoulders only 3% wider than the hips. Because of this, men tend to spread their legs wider to incorporate this ratio.
You may even observe one man after another all manspreading next to each otherwhat gives!? It turns out if one man spreads his legs, other men around him will usually mirror to maintain status unless they are submissive1.
What it Means: This posture means confidence. Just as the name implies, the seated-readiness position means someone is ready to take action! Whether its to get up and leave or to make an important decision, this cue is important especially in negotiations.
How to Use it: Take this position at the end of a long meeting or when you want to end a conversation early. This can make you appear action-oriented and enthusiastic, but depending on the context can also make you appear impatient or impolite.
What it Means: People usually tuck their legs in when theyre feeling comfortable. But pay close attention to the knee that is folded underneath. Where its pointing is likely the person they are most interested in or have the most chemistry with!
What it Means: This cue implies an ultra-relaxed attitude and is often used by professionals like accountants, lawyers, and sales managers. Catapulting takes up a huge amount of space (just like the name suggests), and signals high dominance and confidence.
In a study of one insurance company, the Peases found that 27 out of 30 of the male sales managers used the Catapult position regularly around other salespeople or subordinates, but rarely when around superiors. With their superiors, they were likely to use submissive and subordinate cues instead.
In most late-night talk shows, such as Jimmy Kimmel Live! Or Late Night with Conan OBrien, women guests will often cross their legs like this:SrcWhat does this cue indicate?1. Convenience2. Comfort3. Chemistry4. All of the Above
The answer is d) all of the above! Women who do this often wear skirts, so they cross their legs to protect their vulnerable bits. Theyll also cross because its naturally comfortable, and their knee will usually point towards the host, signalling mutual chemistry.
Comfort: We tend to cross our legs when we feel comfortable, confident, and relaxed. For some people this is a naturally comfortable posture, and women who wear short skirts will often cross their legs. Others will cross to shift their weight if their legs are feeling tired.
Threats: On the downside, if someone we dont like suddenly appears, we might immediately uncross our legs and sit more upright3. For example, if we are alone in an elevator with our legs crossed and a stranger suddenly comes in, well likely uncross our legs. This is because crossed legs decreases our balance, and we want to be ready when a threat appears.
Dislike: Gerard I. Nierenberg and Henry H. Calero, authors of How to Read a Person Like a Book, studied over 2,000 negotiations and found that none of the negotiators had their legs crossed when a deal was made. This is because crossing legs can be a closed-off cue. This body language is also common when someone is new to a group of people. If you see a person standing or sitting with legs crossed, theres a chance theyre feeling submissive or defensive.
How to Use it: Since people cross for a variety of reasons, the key to reading this cue is to take other body language cues into context. If a person is crossed but smiling with their arms to their side, they may be relaxed. But if theyre crossing legs, crossing their arms, and looking down, they might be feeling negative.
What it Means: The figure 4 isnt just a sitting position. Its one of the most dominant sitting positions you can do while also remaining subtle. This is the position Western cowboys sat in. It also displays the family jewels openly and takes up more physical space than sitting in a neutral position or a closed cross, which is a way to claim territory.
We were all shocked to find out that Lance Armstrong had been involved with illegal substances throughout his seven Tour De France wins. His interview with Oprah, however, showed more anger, pride and defiance than sadness and regret.
How to Use it: Prop your leg up in the figure 4 if you want to close down or create a barrier between you and the other person. Be careful to do this in parts of the Middle East or Asia, however, as showing the dirty soles of your shoes can be insulting!
Otherwise, keep your feet grounded. Studies show that people make most of their final decisions when both feet are on the ground1. Therefore, the figure 4 is not helpful when trying to make a decision.
As a variation of the Figure 4, the Leg Clamp happens when someone grabs their bent leg, forming a more structured barrier between them and everyone else. This is a very stubborn and competitive gesture that should only be used to shut people down.
The next time you see an argument (or are in one yourself!), observe the legs. Chances are, if a persons legs were close together, they are now far apart. And the further apart they get, the more increasingly unhappy they become.
Its such a dominant move that Navarro even tells law enforcement and executives to avoid using this move if they want to build trust. Even psychopaths have been known to use the battle stance along with eye gaze to control others.
It can also be a very neutral stance for some people. In this case, they may also have neutral feelings and have no commitment to stay or go during a conversation1. Youll often see women using the solider stance more in female-male interactions as a no comment signal.
In other cases, people who stiffen up suddenly may feel hesitant or nervous, and not in control of a situation. If thats the case, pay attention to a persons eyes to see if they widen and watch their mouth to see if it slightly opens. This may indicate theyre feeling scared during a situation.
Excess Energy: Shaking legs signals excess energy and a desire to release that energy somewhere. Most people dont release by screaming or flailing about wildly, so their extra energy manifests itself in the leg shake.
Boredom: Did you know leg shaking can increase concentration? Studies show that some children with ADHD perform repetitive movements like leg shaking to help ease boredom so they can concentrate better.
What it Means: Leg cleansing is a very significant cue that occurs quickly in reaction to a negative event4.Navarro observed this cue for years whenever suspects are presented with conclusive evidence.
Sometimes the leg cleanse is only done once. But it can also be done repeatedly when someone needs extra reassurance, and also increases in intensity when stress increases.. Whenever we cleanse, it serves 2 purposes:
When you see leg touching repeatedly, such as self-massaging the legs or repeating the same gesture, this can indicate high stress. We often massage ourselves or provide repetitive stimulation in order to calm our nerves down.
Have you ever seen someone scratch their ankles? I remember one time I saw a business partner giving updates about her potential lead. She ankle scratched, and needless to say wasnt too happy with the outcome.
But sometimes our ankles just get itchy. And conveniently enough, researchers found out that the ankle scratch is the King of all scratches. In other words, scratching the ankle gives the most pleasure when compared to scratching the forearm or back.
What it Means: This is NOT a great posture to use, especially on stage. In my past trainings, Ive seen this cue used many times. But the thing is it strips women of their confidence! Not only are they not firmly planted on the floor, the wobbliness of this posture makes their words sound less powerful.
What it Means: The Buttress stance, according to Elizabeth Kuhnke, indicates that a person is ready to leave. The shift to the back of their leg is opposite of the forward lean and signals they want an exit to the conversation.
Have you heard about the new photogenic pose thats going viral? Its called Jazz Legs. This pose is similar to the Buttress Stance, with the weight shifted to the back leg. Except the back leg is bent and the front leg is kept straight.
Side Note: As much as possible we tried to use academic research or expert opinion for this master body language guide. Occasionally, when we could not find research we include anecdotes that are helpful. As more research comes out on nonverbal behavior we will be sure to add it!
Vanessa Van Edwards is a national best selling author & founder at Science of People. Her groundbreaking book, Captivate: The Science of Succeeding with People has been translated into more than 16 languages. As a recovering awkward person, Vanessa helps millions find their inner charisma. She regularly leads innovative corporate workshops and helps thousands of individual professionals in her online program People School. Vanessa works with entrepreneurs, growing businesses, and trillion dollar companies; and has been featured on CNN, BBC, CBS, Fast Company, Inc., Entrepreneur Magazine, USA Today, the Today Show and many more.
This is typically a relaxed posture and it could mean they are simply resting their upper torso by leaning their arms on their legs. If they are leaning forward, it could mean they are in a ready position and want to leave. The key here is paying attention to the rest of their body to see what theyre really feeling! Hope this helps. Rob | Science of People Team