Calculation The coefficient of permeability can be expressed by the relation. Proctor developed a laboratory compaction test procedure to determine the maximum dry unit weight of compaction of soils which can be used for specification of field compaction.
This test is referred to as the' standard Proctor compaction test and is based on the compaction of the soil fraction passing No, 4 U. Compaction mold 2. Standard Proctor hammer 5.
Large flat pan 7. Jack 8. Steel straight edge 9. Moisture cans Drying oven Equipment for Proctor compaction test. Proctor Compaction Mold and Hammer A schematic diagram of the Proctor compaction mold, which is 4 in.
There is a base plate and an extension. The inside of the mold is Iho ft3 ;9 cm3. Figure b shows the schematic diagram of a standard Proctor hammer. The hammer can be lifted and dropped through a vertical distance of 12 in. Obtain about 10 lb 4. Break all the soil lumps. Sieve the soil on a No. Collect all of the minus-4 material in a large pan. This should be about 6lb 2. Now attach the extension to the top of the mold.
Each layer should be com- pacted uniformly by the standard Proctor hammer 25 times before the next layer of loose soil is poured into the mold. Standard Proctor mold and hammer. Note: The layers of loose soil that are being poured into the mold should be such that, at the end ofthe three-layer compaction, the soil should extend slightly above the top of the rim of the compaction mold.
Remove the top attachment from the mold. Be careful not to break off any of the compacted soil inside the mold while removing the top attachment. Now the top of the compacted soil will be even with the top of the mold.
Remove the base plate from the mold. Take a moisture can and determine its mass, W3 g. Place the moisture can with the moist soil in the oven to dry to a constant weight. Break the rest ofthe compacted soil to No. Excess soil being trimmed Step 8. Repeat Steps 6 through Continue the test until at least two successive down readings are obtained. Soil Mechanics Laboratory Manual This can be given by Table shows the calculations for Yzav for the soil tested and re- ported in Table Also dete.
Figure shows the results of calculations made in Tables and Weight of mold, WI lb Weight of moist soil, W2 - WI 3. Moisture can number 6. Mass of moisture can, W3 g I Plot of Vd VS. For further discussion on this topic, refer to Das However, ASTM and AASHTO have four different methods for the standard Proctor com- paction test that reflect the size of the mold, the number of blows per layer, and the maximum particle size in a soil used for testing.
Summaries of these methods are given in Table Because of this, in the initial stages of com- paction, the dry unit weight of compaction increases. However another factor that will control the dry unit weight of compaction of a soil at a given moisture content is the energy of com-paction. The hammer used for this test weighs 10 lb and drops through a vertical distance of 18 in. Figure 13'-1 shows the standard and modified Proctor test hammers side by side.
The compaction mold used in this test is the same as described in Chapter 12 i. Comparison of the standard and modified Proctor compaction hammer. Note: The left-side hammer is for the modified Proctor compaction test.
Procedure The procedure is the same as described in Chapter 12, except for Item 6. The moist soil has to be poured into the mold in five equal layers. Each layer has to be compacted by the modi- fied Proctor hammer with 25 blows per layer.
Soil Mechanics Laboratory Manual 91 Comparison of standard and modified, Proctor compaction test results for the soil reported in Tables and General Comments 1. The modified Proctor compaction test results for the same soil as reported in Tables and and Fig. A comparison ofy dVs. However, for a given void ratio, an increase in the angularity of the soil particles will give a higher value of the soil friction angle.
The general range of the angle of friction of sand with relative density is shown in Fig. Direct shear test machine strain controlled 2.
Large porcelain evaporating dish 4. Tamper for compacting sand in the direct shear box " 5. Spoon Figure shows a direct shear test machine. It consists primarily of a direct shear box, which is split into two halves top and bottom and which holds the soil specimen; a proving ring to measure the horizontal load applied to the specimen; two dial gauges one horizontal and one vertical to measure the deformation of the soil during the test; and a yoke by which a vertical load can be applied to the soil specimen.
A horizontal load to the top half of the shear box is applied by a motor and gear arrangement. In a strain-controlled unit, the rate of movement of the top half of the shear box can be controlled. General range of the variation of angle of friction of sand with relative density of compaction. Figure shows a direct shear test machine.
It consists primarily of a direct shear box, which is split into two halves top and bottom and which holds the soil specimen; a proving ring to measure the horizontal load applied to a specimen; two dial gauges one horizontal and one vertical to measure the deformation of the soil during the test; and a yoke by which a vertical load can be applied to the soil specimen. In a strain-controlled unit, the rate of movement on the top half of the shear box can be controlled. Figure shows the schematic diagram of the shear box.
The shear box is split into two halves-top and bottom. The top and bottom halves of the shear box can be held together by two vertical pins. There is a loading head which can be slipped from the top of the shear box to rest on the soil specimen inside the box. There are also three vertical screws and two horizontal screws on the top half of the shear box. Remove the shear box assembly.
Back off the thrt;e vertical and two horizontal screws. Remove the loading head. Insert the two vertical pins to keep the two halves of the shear box together. Weigh some dry sand in a large porcelain dish, WI' Fill the shear box with sand in small layers. A tamper may be used to compact the sand layers. The top of the compacted specimen should be about Y. Level the surface of the sand specimen. A direct shear test machine.
Determine the dimensions of the soil specimen i. Slip the loading head down from the top of the shear box to rest on the soil specimen. Put the shear box assembly in place in the direct shear machine.
N, on the specimen. This can be done by hanging dead weights to the vertical load yoke. The top crossbars will rest on the loading head of the specimen which, in tum, rests onthe soil specimen. Remove the two vertical pines which were inserted in Step 1 to keep the two halves ofthe shear box together.
Advance the three vertical screws that are located on the side walls of the top half of the shear box. This is done to separate the two halves of the box. Schematic diagram of a direct shear test box. Set the loading head by tightening the two horizontal screws located at the top half of the shear box.
Now back off the three vertical screws. After doing this, there will be no connection between the two halves of the shear box except the soil. Attach the horizontal and vertical dial gauges 0. Apply horizontal load, S, to the top half of the shear box.
The rate of shear displace- ment should be between 0. For every tenth small division displacement in the horizontal dial gauge, record the readings of the vertical dial gauge and the proving ring gauge which measures horizontal load, 8. Continue this until after a the proving ring dial gauge reading reaches a maximum and then falls, or b the proving ring dial gauge reading reaches a maximum and then remains constant. Soil Mechanics Laboratory Manual Table Specimen length, L in.
Specimen width, B in: 2 3. Specimen height, H in. Dry unit weight of specime. Specific gravity of soil solids, Gs 2.
Plot of shear stress and vertical displacement vs. Plot of s vs. Note: The results for tests with 0. The unconfined compression test is a quick method of determining the value of Cu for a clayey soil.
The unconfined strength is given by the relation [for further discussion see any soil mechanics text, e. The unconfined compressiou strength is determined by applying an axial stress to a cylin- drical soil specimen with no confining pressure and observing the axial strains corresponding to various. The stress at which failure in the soil specimen occurs is referred to as the unconfined compression strength Figure For saturated clay specimens, the unconfined compression strength decreases with the increase in moisture content.
Unconfined compression strength-definition Equipment 1. Unconfined compression testing device 2. Specimen trimmer and accessories if undisturbed field specimen is used 3. Harvard miniature compaction device and accessories if a specimen is to be molded for classroom work 4.
Scale 5. Porcelain evaporating dish Unconfined Compression Test Machine An unconfined compression test machine in which strain-controiled tests can be performed is shown in Fig. The machine essentially consists of a top and a bottom loading plate. The bottom of a proving ring is attached to the top loading plate. The top of the proving ring is attached to a cross-bar which, in tum, is fixed to two metal posts. The bottom loading plate can be moved up or down. Obtain a soil specimen for the test.
If it is an undisturbed specimen, it has to be trimmed to the proper size by using the specimen trimmer. The cylindrical soil specimen should have a height-to-diameter LID ratio of be- tween 2 and 3. In many instances, specimens with diameters of 1. Soil Mechanics Laboratory Manual Figure An unconfined compression testing machine.
Measure the diameter D and length L of the specimen and detennine the mass of the specimen. Place the specimen centrally between the two loading plates of the unconfined com- pression testing machine. Move the top loading plate very carefully just to touch the top of the specimen. Set the proving ring dial gauge t. A dial gauge [each small division of the gauge should be equal to 0. Set this dial gauge to zero. Turn the machine on. Record loads i. At the initial stage of the test, readings are usually taken every 0.
How- ever,. Continue taking readings until a. A soil specimen after failure b. Load reaches a maximum value and remains approximately constant thereafter take about 5 readings after it reaches the peak value ; or c.
This may happen in the case of soft clays. Figure shows a soil specimen after failure. Unload the specimen by lowering the bottom loading plate. Remove the specimen from between the two loading plates. Draw a free-hand sketch of the specimen after failure. Show the nature of the failure.
Put the specimen in a porcelain evaporating dish and determine the moisture content after drying it in an oven to a constant weight. Calculation For each set of readings refer to Table : I. Calculate the vertical strain Column 2 M Column 3 x calibration factor Proving ring calibration factor: 1 div.
This is the unconfined compression strength, qu' of the specimen. In the detennination of unconfined compression strength, it is better to conduct tests on two to three identical specimens. The average value of qu is the representative value.
Based on the value of qu' the consistency of a cohesive soil is as follows,: Very soft Soft Medium Stiff stiff 3. For many naturally deposited clayey soils, the unconfined compression strength is greatly reduced when the soil is tested after remolding without any change in moisture content.
In this chapter, the procedure of a one-dimensional laboratory consolidation test will be described, aud the methods of calculation to obtain the void ratio- pressure curve e vs.
Consolidation test unit 2. Specimen trimming device 3. Wire saw 4. Balauce sensitive to 0. Stopwatch 6. Moisture cau 7. Oven Consolidation Test Unit The consolidation test unit consists of a consolidometeraud a loading device. The consolido- meter cau be either 1 a floating ring consolidometer Fig. The floating ring consolidometer usually consists of a brass ring in which the soil specimen is placed.
One porous stone is placed at the top ofthe specimen aud auother porous tone at the bottom. The soil speCimen in the ring with the two porous stones is placed on a base plate. A plastic ring surrounding the specimen fits into a groove on the base plate.
Load is applied through a loading head that is placed on the top porous stone. Schematic diagram of a floating ring consolidometer; b fixed ring consolidometer. The fixed ring consolidometer essentially consists of the same components, i. The ring surrounds the soil specimen. A stand pipe is attached to the side of the base plate. This can be used for permeability determination of soil.
In the fixed ring consolidometer, the compression of the specimen occurs from the top towards the bottom. The specifications for the loading devices of the consolidation test unit vary depending upon the manufacturer.
Figure shows one type ofloading device. During the consolidation test, when load is applied to the soil specimen, the nature of variation of side friction between the surrounding brass ring and the specimen are different for the fixed ring and the floating ring consolidometer, and this is shown in Fig. Prepare a soil specimen for the test.
The specimen is prepared by trimming an undis- turbed natural sample obtained in shelby tubes. The shelby tube sample should be about V. Soil Mechanics Laboratory Manual 11 9 Figure Consolidation load assembly. In this assembly, two specimens can be simultaneously tested.
Lever arm ratio for loading is Note: For classroom instruction purposes, a specimen coo be molded in the laboratory. Collect some excess soil that has been trimmed in a moisture can for moisture content determination. Collect some of the excess soil trimmed in Step I for determination of the specific gravity of soil solids, Gs' 4.
Determine the mass of the consolidation ring WI in grams. Place the soil specimen in the consolidation ring. Use the wire saw to trim the speci- men flush with the top and bottom of the consolidation ring. Record the size of the specimen, i. Nature of variation of soil-ring friction per unit contact areas in a fixed ring consolidometer; b floating ring consolidometer. Determine the mass of the consolidation ring and the specimen W2 in grams.
Saturated the lower porous stone on the base of the consolidometer. Place the soil specimen in the ring over the lower porous stone. Place the upper porous stone on the specimen in the ring. Attach the top ring to the base of the consolidometer. Add water to the consolidometer to submerge the soil and keep it saturated.
In the case of the fixed ring consolidometer, the outside ring which is attached to the top of the base and the stand pipe connection attached to the base should be kept full with water. This needs to be done for the entire period of the test. Place the consolidometer in the loading device. Attach the vertical deflection dial gauge to measure the compression of soil. It should be fixed in such as way that the dial is at the beginning of its release run.
Take the vertical deflection dial gauge readings at the following times, t, counted from the time of load application-O min. Soil Mechanics Laboratory Manual 1 21 Repeat Step 15 for soil pressure magnitudes of2 tonlft2 At the end of the test, remove the soil specimen and determine its moisture content.
S iii 0. Plot of dial reading vs. Determination of t 90 by square-root-of-time method. Calculation and Graph The calculation procedure for the test can be explained with reference to Tables and and Figs. Collect all of the time vs.
Draw a tangent AB to the initial consolidation curve. Measure the lengthBC. In Fig. This technique is referred to as the square-root-of-time fitting method Taylor, The procedure for this is shown in Fig.
Consolidation Test Time VS. Moisture Content: Beginning of test The point of intersection of these two lines is A. The vertical dial gauge corresponding to line BC ill d , i. Complete the experimental data in Columns 1, 2, 8 and 9 of Table Determine the height of solids Hs of the specimen in the mold as see top of Table -.
Determine the fmal specimen height, Ht f , at the end of consolidation due to a given load Column 4 in Table Determine the height of voids, Hv, in the specimen atthe end of consolidation due to a given loading, p, as see Column 5 in Table Calculate the coefficient of consolidation, Cv Column 10, Table , from Column 8 as Plot a semilogarithmic graph of pressure vs. Column 6, Table Pressure,p, is plotted on the log scale and the final void ratio on the linear scale.
As an example, the results of Table are plotted in Fig. Note: The plot has a curved upper portion and, after that, e vs. Calculate the compression index, Ce. This is the slope of the linear portion of the e vs. On the semilogarithmic graph Step 13 , using the same horizontal scale the scale for p , plot the values of C v Column 10 and II, Table Note: Cv is plotted on the linear scale corresponding to the average value of p, i.
Plot of void ratio and the coefficient of consolidation against pressure for the soil reported in Table For record Jow Pressure, ;. Let , and 4 correspond to the base and observation deck, respectively. When such a gage is altached to the closed water tank of Fig. What is the absolute air pressure in the tank?
What is the corresponding absolute pressure if the local at- mospheric pressure is kPa abs? Hg corresponds to what value of atmospheric pres- sure in psia, and in pascals? Calculate the heights including the effect of vapor pressure, and compare the results with those obtained neglecting vapor pressure. Do these results support the widespread use of mer- cury for barometers? Determine the reading on the pressure gage for a differential reading of 4 ft on the manometer. Express your answer in psi gage.
The liquid in the top part of the piping system has a specific gravity of 0. The air pres- sure in the tank is 0. The pressure at point A is 2. Determine: a the depth of oil, z, and b the differential reading, h, on the ma- nometer. The fluid in both pipes A and B is water, and the gage fluid in the manometer has a specific gravity of 2.
What is the pressure in pipe B corresponding to the dicferential reading shown? A U-tube manometer is connected to the pipe through pressure taps located 3 in.
Determine the differential reading of the manometer corre sponding to a pressure drop between the taps of 0. Let p and p be pressures at pressure taps. Write manometer eguetion between fp, and p,. This device con- sists of two large reservoirs each having a cross- sectional area, A,, which are filled with a liquid having a specific weight, y,, and connected by a U-tube of cross-sectional area, A,, containing a liquid of specific weight, y.
When a differential gas pressure, p, — p,, is applied a differential Teading, h, develops. It is desired to have this reading sufficiently large so that it can be easily read for small pressure differentials.
Ae a r and tf 4 Vs small Then abh co and Jast term in Eg. Can be heglectea. A mercury barometer lo- cated inside the shell reads mm Hg, and a mercury U-tube manometer designed to give the outside water pressure indicates a differential reading of mm Hg as illustrated. Based on these data what is the atmospheric pressure at the ocean surface?
When the valve at the top of the right leg is open the level of mercury below the valve is h,. After the valve is closed, air pressure is applied to the left leg. Determine the relationship between the differential reading on the manom- eter and the applied gage pressure, p,. Assume that the temperature of the trapped air remains constant.
One way to calibrate this type of gage is to use the arangemeni shown in Fig. The container is filled with a liquid and a weight, W, placed on one Bourdon Gage side with the gage on the other side. The weight acting on the g liquid through a 0. For a particular gage, some data are given below. Based on a plot of these data, determine the relationship between 6 and the pressure, p, where p is measured in psi? Pb psc 7. You can then remove your hand from the card and the card remains in place, holding the water in the glass.
Explain how this works. Each 4-ft-long ferm is held together by four ties—two atthe top and two at the bottom as indicated. A 2-m-diameter hatch is located in an inclined wall and hinged on one edge. Determine the minimum air pressure, p,, within the container to open the hatch. Neglect the weight of the hatch and friction in the hinge. If the seawater stands at a depth of 7 m, what depth of freshwater is required to give a zero resultant force on the wall?
When the resultant force is zero will the moment due to the fluid forces be zero? For Foy this distance 1s af Lim 1. The serees are not tollnear. The circtlar-plate valve fitted in the short ts discharge pipe on the tank pivots about its diameter A-A and is held shut against the water pressure by a latch at B.
Show that the force on the latch is independent of the supply pressure, p, and the Pressure P height of the tank, h. Water acts against the gate which is hinged at point A. Friction in the hinge is negligible. Determine the tension in the cable. The base of the triangle is horizontal and the vertex is above the base. Determine the resultant force the fluid ex- erts on the area when the fluid depth is 20 ft above the base of the triangular area. Show, with the aid of a sketch, where the center of pressure is located.
Determine the magnitude of the resultant force acting on one side of the area as a result of the oil. The gate is hhinged at its bottom and held closed by a horizontal force, Fi, located at the center of the gate, The maximum value for Fyyis KN.
Explain your answer. Determine the horizontal re- Hines action that is developed on the gate at C. Itis held in place by the Ib counterweight, W. Determine the water depth, h. As the bottom of the brace is moved to the right, the water level remains at the top of the gate. The line of action of the force that the brace exerts on the gate is along the brace. Comment on the results as Thus, Eg. Cun be used determine Fy fr 4 given 8. A rectangular gate that is 4m high and 2 m wide and hinged at one end is located in the partition.
Water is slowly added to the empty side of the tank. At what depth, h, will the gate start to open? A fr," Too As, 4. Since, a ae ie a dm Cm? The horizontal portion of the gate covers a 1-ft- diameter drain pipe which contains air at atmospheric pressure.
Determine the minimum water depth, h, at which the gate will pivot to allow water to flow into the pipe. Determine the magnitude and location of the resultant fluid force acting on one end of the tank. By means 08 The depth of fluid in the tank is 3. One side of the vessel contains a spout that is closed by a 6-in. The hor- izontal axis of the hinge is located 10 ft below the Piel aeene water surface. Determine the minimum torque 3 that must be applied at the hinge to hold the gate ay shut.
Neglect the weight of the gate and friction at the hinge. For the dam widths specified, The maximum water depths ave givin below. That is, when the water depth exceeds 4 m, the gate opens slightly and lets the water flow under it, Determine the weight of the gate per meter of length.
Consider the free body diagram: of the gate and a portion of the water asshown. Thus, 0. The trace of the surface is a parabola as illustrated. Determine the moment of the fluid force per unit length with respect to an axis through the toe point A. A ver- tical, 0. The tank and the pipe are filled with ethyl alcohol to a level of 1.
Determine the resultant force of the alcohol on one end of the tank and show where it acts. Thus, the resultant force has a magnitude of Base your analysis on a I-ft length of the bulge. The force of the gate against the block for gate b is R.
Determine in terms of R the force against the blocks for the other two gates. Determine the specific weight of the log. The barge is 28 ft wide and 90 ft long. When unloaded its draft depth of submergence is 5 ft, and with the load of grain the draft is 7 ft.
De- termine: a the unloaded weight of the barge, and b the weight of the grain. It was found that even after 15 years un- derwater the trees were perfectly preserved and underwater log- ging was started.
During the logging process a tree is selected, trimmed, and anchored with ropes to prevent it from shooting to the surface like a missile when cut, Assume that a typical large tree can be approximated as a truncated cone with a base diameter of 8 ft, a top diameter of 2 ft, and a height of ft. Determine the resul:ant vertical force that the ropes must resist when the completely submerged tree is cut. The specific grav- ity of the wood is approximately 0. The amount of air in the tube has been adjusted 50 that it just floats.
The bottle cap is securely fastened. A slight squeezing of the plastic bottle will cause the test tube to sink to the bottom of the bottle. Explain this phenomenon, Whea the test tube is Floating the weight of The tube, I, is balanced by the bueyent Are Fy, 25s shown sr The figure. The bisyent force 13 due te The displaced volume of water 43 shown. This displaced volume is due ts the air pressure, p, trapped si The tube Where pe Br, 4.
Determine the density of the material. Determine the required value for M. Neglect friction at the gate hinge and the pulley. If the water is replaced with a liquid having a specific gravity of 1.
The hydrometer weighs 0. To obtan This difference the change in length, Af a ZF 0. With the new Igual the stem Would Protrude Bis in. What percent of the volume of the iceberg is under water? Determine the organic matter content. Density Unit Weight Determination Purpose: This lab is performed to determine the in-place density of undisturbed soil obtained by pushing or drilling a thin-walled cylinder.
The bulk density is the ratio of mass of moist soil to the volume of the soil sample, and the dry density is the ratio of the mass of the dry soil to the volume the soil sample.
This test can also be used to determine density of compacted soils used in the construction of structural fills, highway embankments, or earth dams. This method is not recommended for organic or friable soils. Extrude the soil sample from the cylinder using the extruder. Cut a representative soil specimen from the extruded sample.
Determine and record the length L , diameter D and mass Mt of the soil specimen. Determine and record the moisture content of the soil w. See Experiment 1 5. Note: If the soil is sandy or loose, weigh the cylinder and soil sample together. Measure dimensions of the soil sample within the cylinder.
Specific Gravity Determination Purpose: This lab is performed to determine the specific gravity of soil by using a pycnometer. Specific gravity is the ratio of the mass of unit volume of soil at a stated temperature to the mass of the same volume of gas-free distilled water at a stated temperature. Determine and record the weight of the empty clean and dry pycnometer, WP. Place 10g of a dry soil sample passed through the sieve No.
Determine and record the weight of the pycnometer containing the dry soil, WPS. Add distilled water to fill about half to three-fourth of the pycnometer. Soak the sample for 10 minutes. Apply a partial vacuum to the contents for 10 minutes, to remove the entrapped air. Stop the vacuum and carefully remove the vacuum line from pycnometer. Fill the pycnometer with distilled water to the mark , clean the exterior surface of the pycnometer with a clean, dry cloth.
Determine the weight of the pycnometer and contents, WB. Empty the pycnometer and clean it. Then fill it with distilled water only to the mark. Clean the exterior surface of the pycnometer with a clean, dry cloth. Determine the weight of the pycnometer and distilled water, WA. Relative Density Determination Purpose: This lab is performed to determine the relative density of cohesionless, free-draining soils using a vibrating table. The relative density of a soil is the ratio, expressed as a percentage, of the difference between the maximum index void ratio and the field void ratio of a cohesionless, free-draining soil; to the difference between its maximum and minimum index void ratios.
The engineering properties, such as shear strength, compressibility, and permeability, of a given soil depend on the level of compaction. Fill the mold with the soil approximately 0.
Spiraling motion should be just sufficient to minimize particle segregation. Trim off the excess soil level with the top by carefully trimming the soil surface with a straightedge.
Determine and record the mass of the mold and soil. Then empty the mold M1. Again fill the mold with soil do not use the same soil used in step 1 and level the surface of the soil by using a scoop or pouring device funnel in order to minimize the soil segregation. The sides of the mold may be struck a few times using a metal bar or rubber hammer to settle the soil so that the surcharge base-plate can be easily placed into position and there is no surge of air from the mold when vibration is initiated.
Place the surcharge base plate on the surface of the soil and twist it slightly several times so that it is placed firmly and uniformly in contact with the surface of the soil. Remove the surcharge base-plate handle. Attach the mold to the vibrating table. Determine the initial dial reading by inserting the dial indicator gauge holder in each of the guide brackets with the dial gage stem in contact with the rim of the mold at its center on the both sides of the guide brackets.
Obtain six sets of dial indicator readings, three on each side of each guide bracket. The average of these twelve readings is the initial dial gage reading, Ri. Record Ri to the nearest 0. Firmly attach the guide sleeve to the mold and lower the appropriate surcharge weight onto the surcharge base-plate.
Vibrate the mold assembly and soil specimen for 8 min. Determine and record the dial indicator gage readings as in step 7. The average of these readings is the final dial gage reading, Rf. Remove the surcharge base-plate from the mold and detach the mold from the vibrating table. Determine and record the mass of the mold and soil M2 Empty the mold and determine the weight of the mold. Determine and record the dimensions of the mold i.
Also, determine the thickness of the surcharge base-plate, Tp. Analysis: 1. Atterberg Limits Purpose: This lab is performed to determine the plastic and liquid limits of a fine grained soil. The plastic limit PL is the water content, in percent, at which a soil can no longer be deformed by rolling into 3.
A third limit, called the shrinkage limit, is used occasionally. The Atterberg limits are based on the moisture content of the soil. The plastic limit is the moisture content that defines where the soil changes from a semi-solid to a plastic flexible state. The liquid limit is the moisture content that defines where the soil changes from a plastic to a viscous fluid state. The shrinkage limit is the moisture content that defines where the soil volume will not reduce further if the moisture content is reduced.
A wide variety of soil engineering properties have been correlated to the liquid and plastic limits, and these Atterberg limits are also used to classify a fine-grained soil according to the Unified Soil Classification system or AASHTO system. Assume that the soil was previously passed through a No. Thoroughly mix the soil with a small amount of distilled water until it appears as a smooth uniform paste.
Cover the dish with cellophane to prevent moisture from escaping. Weigh four of the empty moisture cans with their lids, and record the respective weights and can numbers on the data sheet. Adjust the liquid limit apparatus by checking the height of drop of the cup. The point on the cup that comes in contact with the base should rise to a height of 10 mm. The block on the end of the grooving tool is 10 mm high and should be used as a gage.
Practice using the cup and determine the correct rate to rotate the crank so that the cup drops approximately two times per second. Place a portion of the previously mixed soil into the cup of the liquid limit apparatus at the point where the cup rests on the base.
Squeeze the soil down to eliminate air pockets and spread it into the cup to a depth of about 10 mm at its deepest point. The soil pat should form an approximately horizontal surface See Photo B. Use the grooving tool carefully cut a clean straight groove down the center of the cup.
The tool should remain perpendicular to the surface of the cup as groove is being made. Use extreme care to prevent sliding the soil relative to the surface of the cup See Photo C. Make sure that the base of the apparatus below the cup and the underside of the cup is clean of soil. See Photo D. If the number of drops exceeds 50, then go directly to step eight and do not record the number of drops, otherwise, record the number of drops on the data sheet.
Take a sample, using the spatula, from edge to edge of the soil pat. The sample should include the soil on both sides of where the groove came into contact. Place the soil into a moisture can cover it. Immediately weigh the moisture can containing the soil, record its mass, remove the lid, and place the can into the oven. Leave the moisture can in the oven for at least 16 hours. Place the soil remaining in the cup into the porcelain dish.
Clean and dry the cup on the apparatus and the grooving tool. Remix the entire soil specimen in the porcelain dish. Add a small amount of distilled water to increase the water content so that the number of drops required closing the groove decrease. Repeat steps six, seven, and eight for at least two additional trials producing successively lower numbers of drops to close the groove.
One of the trials shall be for a closure requiring 25 to 35 drops, one for closure between 20 and 30 drops, and one trial for a closure requiring 15 to 25 drops. Determine the water content from each trial by using the same method used in the first laboratory. Remember to use the same balance for all weighing.
Weigh the remaining empty moisture cans with their lids, and record the respective weights and can numbers on the data sheet. Form the soil into an ellipsoidal mass See Photo F. Roll the mass between the palm or the fingers and the glass plate See Photo G. Use sufficient pressure to roll the mass into a thread of uniform diameter by using about 90 strokes per minute.
A stroke is one complete motion of the hand forward and back to the starting position. The thread shall be deformed so that its diameter reaches 3. When the diameter of the thread reaches the correct diameter, break the thread into several pieces. Knead and reform the pieces into ellipsoidal masses and re-roll them.
Continue this alternate rolling, gathering together, kneading and re-rolling until the thread crumbles under the pressure required for rolling and can no longer be rolled into a 3. Gather the portions of the crumbled thread together and place the soil into moisture can, and then cover it.
If the can does not contain at least 6. Repeat steps three, four, and five at least two more times. Analysis: Liquid Limit: 1. Calculate the water content of each of the liquid limit moisture cans after they have been in the oven for at least 16 hours. Plot the number of drops, N, on the log scale versus the water content w. Draw the best- fit straight line through the plotted points and determine the liquid limit LL as the water content at 25 drops.
Plastic Limit: 1. Calculate the water content of each of the plastic limit moisture cans after they have been in the oven for at least 16 hours. Compute the average of the water contents to determine the plastic limit, PL. Check to see if the difference between the water contents is greater than the acceptable range of two results 2.
Report the liquid limit, plastic limit, and plasticity index to the nearest whole number, omitting the percent designation. Grain Size Distribution Sieve Analysis and Hydrometer Analysis Purpose: This test is performed to determine the percentage of different grain sizes contained within a soil. The mechanical or sieve analysis is performed to determine the distribution of the coarser, larger-sized particles, and the hydrometer method is used to determine the distribution of the finer particles.
Grain size analysis provides the grain size distribution, and it is required in classifying the soil. Write down the weight of each sieve as well as the bottom pan to be used in the analysis. Record the weight of the given dry soil sample. Make sure that all the sieves are clean, and assemble them in the ascending order of sieve numbers 4 sieves at top and sieves at bottom.
Place the pan below sieves. Carefully pour the soil sample into the top sieve and place the cap over it. Place the sieve stack in the mechanical shaker and shake for 10 minutes. Remove the stack from the shaker and carefully weigh and record the weight of each sieve with its retained soil.
In addition, remember to weigh and record the weight of the bottom pan with its retained fine soil. Hydrometer Analysis: 1. Stir the mixture until the soil is thoroughly wet. Let the soil soak for at least ten minutes. While the soil is soaking, add mL of dispersing agent into the control cylinder and fill it with distilled water to the mark.
Take the reading at the top of the meniscus formed by the hydrometer stem and the control solution. This reading is called the zero correction. Shake the control cylinder in such a way that the contents are mixed thoroughly.
Insert the hydrometer and thermometer into the control cylinder and note the zero correction and temperature respectively. Transfer the soil slurry into a mixer by adding more distilled water, if necessary, until mixing cup is at least half full. Then mix the solution for a period of two minutes.
Immediately transfer the soil slurry into the empty sedimentation cylinder. Add distilled water up to the mark. Cover the open end of the cylinder with a stopper and secure it with the palm of your hand. Then turn the cylinder upside down and back upright for a period of one minute.
The cylinder should be inverted approximately 30 times during the minute. Set the cylinder down and record the time. Remove the stopper from the cylinder.
After an elapsed time of one minute and forty seconds, very slowly and carefully insert the hydrometer for the first reading. Note: It should take about ten seconds to insert or remove the hydrometer to minimize any disturbance, and the release of the hydrometer should be made as close to the reading depth as possible to avoid excessive bobbing.
The reading is taken by observing the top of the meniscus formed by the suspension and the hydrometer stem. The hydrometer is removed slowly and placed back into the control cylinder.
Very gently spin it in control cylinder to remove any particles that may have adhered. Take hydrometer readings after elapsed time of 2 and 5, 8, 15, 30, 60 minutes and 24 hours. Data Analysis: Sieve Analysis: 1. The sum of these retained masses should be approximately equals the initial mass of the soil sample. A loss of more than two percent is unsatisfactory. Calculate the percent retained on each sieve by dividing the weight retained on each sieve by the original sample mass.
Calculate the percent passing or percent finer by starting with percent and subtracting the percent retained on each sieve as a cumulative procedure.
For the No. For No. Make a semilogarithmic plot of grain size vs. Compute Cc and Cu for the soil. Apply meniscus correction to the actual hydrometer reading. From Table 1, obtain the effective hydrometer depth L in cm for meniscus corrected reading. For known Gs of the soil if not known, assume 2. Calculate the equivalent particle diameter by using the following formula: Where t is in minutes, and D is given in mm. Determine the temperature correction CT from Table 3.
Calculate percent finer as follows: Where WS is the weight of the soil sample in grams 9. Plot the grain size curve D versus the adjusted percent finer on the semilogarithmic sheet. Visual Classification Purpose: Visually classify the soils.
For example, as soon as a ground is identified as gravel, engineer can immediately form some ideas on the nature of problems that might be encountered in a tunneling project. In contrast, a soft clay ground is expected to lead to other types of design and construction considerations. Therefore, it is useful to have a systematic procedure for identification of soils even in the planning stages of a project. Soils can be classified into two general categories: 1 coarse grained soils and 2 fine grained soils.
Examples of coarse-grained soils are gravels and sands. Examples of fine-grained soils are silts and clays. Procedures for visually identifying these two general types of soils are described in the following sections. Equipment: Magnifying glass optional Identification Procedure: a. Identify the color e. If the major soil constituent is sand or gravel: Identify particle distribution.
Describe as well graded or poorly graded. Well-graded soil consists of particle sizes over a wide range. Poorly graded soil consists of particles which are all about the same size. Identify particle shape angular, sub-angular, rounded, sub-rounded using Figure 1 and Table 2. Is our service is satisfied, Anything want to say? Cancel reply. Please enter your comment! Please enter your name here. You have entered an incorrect email address! Leave this field empty. Trending Today.
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