The reason for this is that particles would slide over each other at greater slopes. As a consequence of this phenomenon many countries in deltas of large rivers are very flat. It has also caused the failure of dams and embankments all over the world, sometimes with very serious consequences for the local population. Especially dangerous is that in very fine materials, such as clay, a steep slope is often possible for some time, due to capillary pressures in the water, but after some time these capillary pressures may vanish perhaps because of rain , and the slope will fail.
Dilatancy Shear deformations of soils often are accompanied by volume changes. Loose sand has a tendency to contract to a smaller volume, and densely packed sand can practically deform only when the volume expands somewhat, making the sand looser. This is called dilatancy, a phenomenon discovered by Reynolds, in This property causes the soil around a human foot on the beach near the water line to be drawn dry during walking.
The densely packed sand is loaded by the weight of the foot, which causes a shear deformation, which in turn causes a volume expansion, which sucks in some water from the surrounding soil. Creep The deformations of a soil often depend upon time, even under a constant load. This is called creep. Clay and peat exhibit this phenomenon. It causes structures founded on soft soils to show ever increasing settlements.
A new road, built on a soft soil, will continue to settle for many years. For buildings such settlements are particular damaging when they are not uniform, as this may lead to cracks in the building.
Groundwater A special characteristic of soil is that water may be present in the pores of the soil. This water contributes to the stress transfer in the soil. It may also be flowing with respect to the granular particles, which creates friction stresses between the fluid and the solid material. As it takes some time before water can be expelled from a soil mass, the presence of water usually prevents rapid volume changes.
Unknown initial stresses Soil is a natural material, created in historical times by various geological processes. Therefore the initial state of stress is often not uniform, and often even partly unknown. Because of the non-linear behavior of the material, mentioned above, the initial stresses in the soil are of great importance for the determination of soil behavior under additional loads.
These initial stresses depend upon geological history, which is never exactly known, and this causes considerable uncertainty. In particular, the initial horizontal stresses in a soil mass are usually unknown. The initial vertical stresses may be determined by the weight of the overlying layers.
This means that the stresses increase with depth, and therefore stiffness and strength also increase with depth. The horizontal stresses, however, usually remain largely unknown. Variability The creation of soil by ancient geological processes also means that soil properties may be rather different on different locations. Even in two very close locations the soil properties may be completely different, for instance when an ancient river channel has been filled with sand deposits.
Sometimes the course of an ancient river can be traced on the surface of a soil, but often it cannot be seen at the surface. When an embankment is built on such a soil, it can be expected that the settlements will vary, depending upon the local material in the subsoil. The variability of soil properties may also be the result of a heavy local load in the past.
Grain size Soils are usually classified into various types. In many cases these various types also have different mechanical properties. A simple subdivision of soils is on the basis of the grain size of the particles that constitute the soil. Coarse granular material is often denoted as gravel and finer material as sand. In order to have a uniformly applicable terminology it has been agreed internationally to consider particles larger than 2 mm, but smaller than 63 mm as gravel.
Larger particles are denoted as stones. Sand is the material consisting of particles smaller than 2 mm, but larger than 0. Particles smaller than 0. Soil consisting of even smaller particles, smaller than 0.
Table 1: Grain sizes The grain size may be useful as a first distinguishing property of soils, but it is not very useful for the mechanical properties. Soils of the same grain size may have different mechanical properties. Sand consisting of round particles, for instance, can have a strength that is much smaller than sand consisting of particles with sharp points.
Also, a soil sample consisting of a mixture of various grain sizes can have a very small permeability if the small particles just fit in the pores between the larger particles. The size of the particles in a certain soil can be represented graphically in a grain size diagram, see Figure 5. Such a diagram indicates the percentage of the particles smaller than a certain diameter, measured as a percentage of the mass or weight. A steep slope of the curve in the diagram indicates a uniform soil; a shallow slope of the diagram indicates that the soil contains particles of strongly different grain sizes.
For rather coarse particles, say larger than 0. Figure 5: Grain size diagram. Chemical composition Besides the difference in grain size, the chemical composition of soil can also be helpful in distinguishing between various types of soils. Sand and gravel usually consist of the same minerals as the original rock from which they were created by the erosion process.
This can be quartz, feldspar or glimmer. In Western Europe sand usually consists mainly of quartz. The chemical formula of this mineral is SiO2. Fine-grained soils may contain the same minerals, but they also contain the so-called clay minerals, which have been created by chemical erosion. Consistency limits For very fine soils, such as silt and clay, the consistency is an important property. It determines whether the soil can easily be handled, by soil moving equipment, or by hand.
The consistency is often very much dependent on the amount of water in the soil. This is expressed by the water content w. It is then said to be in the solid state. In order to distinguish between these states solid, plastic and liquid two standard tests have been agreed upon, that indicate the consistency limits.
When the porosity is small the soil is called densely packed, when the porosity is large it is loosely packed. It may be interesting to calculate the porosities for two particular cases.
The first case is a very loose packing of spherical particles, in which the contacts between the spheres occur in three mutually orthogonal directions only. This is called a cubic array of particles, see Figure 6. This is the loosest packing of spherical particles that seems possible. Of course, it is not stable: any small disturbance will make the assembly collapse.
Figure 6: Cubic array Figure 7: Densest array Degree of saturation The pores of a soil may contain water and air. Density For the description of the density and the volumetric weight of a soil, the densities of the various components are needed.
The density of a substance is the mass per unit volume of that substance. Small deviations from this value may occur due to temperature differences or variations in salt content. Soils, however, have a number of properties that distinguish it from other materials. Firstly, a special property is that soils can only transfer compressive normal stresses, and no tensile stresses. Secondly, shear stresses can only be transmitted if they are relatively small compared to the normal stresses.
Furthermore it is characteristic of soils that part of the stresses is transferred by the water in the pores. Figure 8: Stresses Because the normal stresses in soils usually are compressive stresses only, it is standard practice to use a sign convention for the stresses that is just opposite to the sign convention of classical continuum mechanics, namely such that compressive stresses are considered positive, and tensile stresses are negative.
The sign convention for the stress components is illustrated in Figure 8. Its formal definition is that a stress component is positive when it acts in positive coordinate direction on a plane with its outward normal in negative coordinate direction, or when it acts in negative direction on a plane with its outward normal in positive direction. This means that the sign of all stress components is just opposite to the sign that they would have in most books on continuum mechanics or applied mechanics.
If such a soil does not carry a local surface load, and if the groundwater is at rest, the vertical stresses can be determined directly from a consideration of vertical equilibrium. A simple case is homogeneous layers, completely saturated with water, see Figure 9. The pressure in the water is determined by the location of the phreatic surface. This is defined as the plane where the pressure in the groundwater is equal to the atmospheric pressure.
If there are no capillary effects in the soil, this is also the upper boundary of the water, which is denoted as the groundwater table.
In the example it is assumed that the phreatic surface coincides with the soil surface, see Figure 9. It has been assumed that there are no shear stresses on the vertical planes bounding the column in horizontal direction. Figure 9: Stresses in a homogeneous layer That seems to be a reasonable assumption if the terrain is homogeneous and very large, with a single geological history.
Often this is assumed, even when there are no data. Because the groundwater is at rest, the pressures in the water will be hydrostatic. The soil can be considered to be a container of water of very complex shape, bounded by all the particles, but that is irrelevant for the actual pressure in the water. That is a consequence of the linear distribution of the total stresses and the pore pressures, with both of them being zero at the same level, the soil surface.
It should be noted that the vertical stress components, both the total stress and the pore pressures, with both of them being zero at the same level, the soil surface.
Pore pressures Soil is a porous material, consisting of particles that together constitute the grain skeleton. In the pores of the grain skeleton a fluid may be present: usually water. The pore structure of all normal soils is such that the pores are mutually connected.
The water fills a space of very complex form, but it constitutes a single continuous body. In this water body a pressure may be transmitted, and the water may also flow through the pores. The pressure in the pore water is denoted as the pore pressure.
Residual and Transported Soils Soils which are formed by weathering of rocks may remain in position at the place of region. These may get transported from the place of origin by various agencies such as wind, water, ice, gravity, etc. Residual soils differ very much from transported soils in their characteristics and engineering behaviour.
The degree of disintegration may vary greatly throughout a residual soil mass and hence, only a gradual transition into rock is to be expected. An important characteristic of these soils is that the sizes of grains are not definite because of the partially disintegrated condition. The grains may break into smaller grains with the application of a little pressure.
Residual soils tend to be more abundant in humid and warm zones where conditions are favourable to chemical weathering of rocks and have sufficient vegetation to keep the products of weathering from being easily transported as sediments. Residual soils have not received much attention from geotechnical engineers because these are located primarily in undeveloped areas.
Soils transported by rivers and streams: Sedimentary clays. Soils transported by wind: loess. Soils transported by glaciers: Glacial till. Soils deposited in lake beds: Lacustrine silts and lacustrine clays. Soils deposited in sea beds: Marine silts and marine clays. Broad classification of soils may be: 1. Coarse-grained soils, with average grain-size greater than 0. Fine-grained soils, with average grain-size less than 0. These exhibit different properties and behaviour but certain general conclusions are possible even with this categorisation.
In a broader sense, consideration of mineralogical composition, electrical properties, orientation and shape of soil grains, nature and properties of soil water and the interaction of soil water and soil grains, also may be included in the study of soil structure, which is typical for transported or sediments soils.
Structural composition of sedimented soils influences, many of their important engineering properties such as permeability, compressibility and shear strength.
Hence, a study of the structure of soils is important. Various national and international Standards specify a range of procedures and equipment necessary to ensure representative sampling. With the use of simple hand tools, it is often possible to obtain detailed information regarding the sub-surface structure and hence the likely engineering characteristics of the area under investigation.
Soil Colour Charts A standard identification of colour is an essential component of a soil-profile description. Soil colour charts are widely used by civil engineers, agronomists, soil scientists, geologists and archaeologists as a means of providing a standard colour reference. The following ranges of mixers provide an efficient means of mixing samples.
Hand Boring and Sampling The items listed provide the engineer with an economic range of equipment for field survey work. Using this equipment it is possible to obtain disturbed or undisturbed samples at reasonable depths, subject to ground conditions. Most items may be inter-connected. Soil and Gravel Auger Heads These auger heads are suitable for boring in cohesive soils or sands and gravels.
The soil augers are constructed of heavy duty steel plates forming an open tube partly interlocked at the cutting end. Gravel augers comprise a one piece steel casting with a spiral point and two plates designed to close when lifting samples from the borehole.
The Dutch Auger is of similar construction to the Soil Augers and is particularly useful in very fine silt-clay sands. Large Sample Splitter This splitter is designed for the reduction of test samples which are too large in volume to be conveniently handled. It divides samples so that half is representative of the original total sample and handles material up to 6 inches in particle size. The lever-actuated unit is constructed of heavy gauge welded steel with a hopper which holds up to 1 ft3.
The single splitter chute provides wide flexibility in sizes of opening and adjustment is provided for chutes of 0. Overall height approximately is 1 metre. Hopper size mm long x mm wide approx. For most purposes crushing of individual particles must be avoided. This reduction process is best achieved using a porcelain mortar and rubber headed pestle.
Moisture Content The new range of Speedy Moisture testers now includes an electronic balance and a heavy duty plastic case. Designed for the most demanding on-site conditions, the new waterproof and durable case offers high levels of protection. The new model comprises: Speedy Moisture tester, electronic balance, beaker, cleaning cloth, cap, washer, scoop, steel pulverizing balls, and cleaning brushes.
Soil Index Properties Soil index properties are used extensively by engineers to discriminate between the different kinds of soil within a broad category, e. Classification tests to determine index properties will provide engineers with valuable information when the results are compared against empirical data relative to the index properties determined. Determination of Liquid Limit The condition of a soil can be altered by changing the moisture content.
The liquid limit is the empirically established moisture content at which a soil passes from the plastic to the liquid state. Knowledge of the liquid limit allows the engineer to correlate several engineering properties with the soil.
Two main types of test are used. The cam mechanism and cup suspension assembly have been designed to withstand constant use with minimum readjustment. The test is based on the relationship between moisture content and the penetration of a cone into the soil sample under controlled conditions.
Determination of Plastic Limit The plastic limit is defined as the lowest moisture content of a soil that will permit a sample to be rolled into threads of 3 mm diameter without the threads breaking. The apparatus required is simple yet effective. The majority of the apparatus required for this test is standard laboratory equipment. For full details see the Laboratory equipment section of the catalogue Determination of Shrinkage Characteristics When the water content of a fine-grained soil is reduced below the plastic limit, shrinkage of the soil mass continues until the shrinkage limit is reached.
Shrinkage can be significant in clays but less so in silts and sands. The equipment listed below enables the engineer to determine a number of important parameters, including shrinkage ratio, volumetric shrinkage and linear shrinkage. The density of a mass of soil is of interest to the engineer for a variety of reasons including the design of earthworks and foundations and in slope stability analysis.
Particle density or specific gravity is a measure of the actual particles which make up the soil mass and is defined as the ratio of the mass of the particles to the mass of the water they displace. Knowledge of the particle density is essential in relation to other soil tests. It is used when calculating porosity and voids ratio and is particularly important when compaction and consolidation properties are being investigated. The majority of apparatus used for the various tests is general laboratory equipment.
Particle Size Distribution and Sand Equivalent Value The analysis of soils by particle size provides a useful engineering classification system from which a considerable amount of empirical data can be obtained. Two separate and different procedures are used. Sieving is used for gravel and sand size particles and sedimentation procedures are used for the finer soils. For soil containing a range of coarse and fine particles it is usual to employ a composite test of sieving and sedimentation procedures.
The Sand Equivalent Test serves as a rapid field test to show the relative proportions of clay-like or plastic fines and dusts in granular soils and fine aggregates. Constant Temperature Bath Specially designed for the sedimentation testing of soils and other fine grained material, the bath is supplied with a false bottom to assist in circulation of the bath liquid. Will accommodate six Sedimentation Cylinders.
The test does not require the weighing accuracy necessary for pipette sedimentation and is suitable for use in site laboratories. Automatic Compaction of Soils The time and effort required preparing specimens for compaction studies and other test methods can often be costly and time-consuming. The height and weight of the rammer are adjustable to suit test requirements. An automatic blow pattern ensures optimum compaction for each layer of soil. The rammer travels across the mould and the table rotates the mould in equal steps on a base that is extremely stable.
The number of blows per layer can be set at the beginning of the test. However, there are numerous ways of preparing samples and in this respect American practice differs in detail from British practice. This test can be performed in the laboratory on prepared samples or on location. It is important to appreciate that this test, being of an empirical nature, is valid only for the application for which it was developed, i. Water Content Determination Purpose: This test is performed to determine the water moisture content of soils.
The consistency of a fine-grained soil largely depends on its water content. The water content is also used in expressing the phase relationships of air, water, and solids in a given volume of soil. Record the moisture can and lid number. Determine and record the mass of empty, clean, and dry moisture can with its lid MC 2. Place the moist soil in the moisture can and secure the lid. Determine and record the mass of the moisture can now containing the moist soil with the lid MCMS.
Leave it in the oven overnight. Remove the moisture can. Carefully but securely, replace the lid on the moisture can using gloves, and allow it to cool to room temperature. Determine and record the mass of the moisture can and lid containing the dry soil MCDS. Empty the moisture can and cleans the can and lid. Data Analysis: 1. Determine the mass of soil solids.
Determine the mass of pore water. Determine the water content. Organic Matter Determination Purpose: This test is performed to determine the organic content of soils. The organic content is the ratio, expressed as a percentage, of the mass of organic matter in a given mass of soil to the mass of the dry soil solids.
Some of the properties influenced by organic matter include soil structure, soil compressibility and shear strength.
In addition, it also affects the water holding capacity, nutrient contributions, biological activity, and water and air infiltration rates. Determine and record the mass of an empty, clean, and dry porcelain dish MP. Place a part of or the entire oven-dried test specimen from the moisture content experiment Expt. Place the dish in a muffle furnace. Gradually increase the temperature in the furnace to oC.
Leave the specimen in the furnace overnight. Remove carefully the porcelain dish using the tongs the dish is very hot , and allow it to cool to room temperature. Determine and record the mass of the dish containing the ash burned soil MPA. Empty the dish and clean it. Determine the mass of the dry soil. Determine the mass of the ashes burned soil. 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. The behavior of pavement may swell, shrink under the various condition of loading environmental effect which causes the failure of the transportation system. Hence, to this kind of problem, we must know of soil mechanics. Earth dams are a huge structure made of soil as a construction material built for creating water reservoirs. To construct it we must have knowledge of consolidation, slope stability, effects of seepage, and consequent settlement as well as compaction characteristics of the soil.
Failure of earth dam may cause a widespread catastrophe, it should be designed and constructed carefully with the help of soil mechanics. For temporary deep excavation, we need to support timbering or bracing. So, excavation requires the knowledge of slope stability analysis, the idea of soil elasticity, isotropic properties. Hence, to gain knowledge about these properties of soil knowledge of soil mechanics is must require.
Besides this, soil mechanics is required to solve the problem relatthe ed to the soil like soil heave, soil subsidence, frost heave, shrinkage, and swelling. Differences between compaction and consolidation process of Soil mass.
Relation between Discharge velocity and Seepage velocity in soil mass. Numerical to calculate the plastic limit of soil Plasticity index. Save my name, email, and website in this browser for the next time I comment. Notify me of follow-up comments by email.
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