MOISTURE CONTENT DETERMINATION
Most laboratory tests in soil mechanics require the determination of water content. Water content is defined as Water content is usually expressed in percent. For better results, the minimum size of the most soil specimens should be approximately as given in Table. These values are consistent with ASTM Test Designation D-2216.
SPECIFIC GRAVITY DETERMINATION
The specific gravity of a given material is defined as the ratio of the weight of a given volume of the material to the weight of an equal volume of distilled water. In soil mechanics, the specific gravity of soil solids (which is often referred to as the specific gravity of soil) is an important parameter for calculation of the weight-volume relationship. ASTM D 854-02 (2004), “Standard Test Methods for Specific Gravity of Soil Solids by Water Pycnometer” is followed for this test.
GRAIN SIZE ANALYSIS
A basic element of a soil classification system is the determination of the amount and distribution of the particle sizes in the soil. The distribution of particle sizes larger than 0.075 mm (No. 200 sieve) is determined by sieving, while a sedimentation process (hydrometer test) is used to determine the distribution of particle sizes smaller than 0.075 mm. The laboratory test procedures for performing a sieve analysis are presented in ASTM D 422.
HYDROMETER TEST
A sedimentation process is used to determine the particle distribution for fines (i.e., silt and clay size particles finer than the No. 200 sieve). A hydrometer is used to obtain the necessary data during the sedimentation process. The hydrometer test is based on Stokes law, which relates the diameter of a single sphere to the time required for the sphere to fall a certain distance in a liquid of known viscosity. The laboratory test procedures for performing a sieve analysis are presented in ASTM D 422.
ATTERBERG LIMITS TESTS
The term plasticity is applied to silts and clays and indicates an ability to be rolled and molded without breaking apart. The Atterberg limits are defined as the water content corresponding to different behavior conditions of silts and clays. Although originally six limits were defined by Albert Atterberg (1911), in geotechnical engineering, the term Atterberg limits only refers to the liquid limit (LL), plastic limit (PL). ASTM D 4318 “Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils” is followed for this test.
DIRECT SHEAR TEST
A direct shear test is a laboratory or field test used by geotechnical engineers to measure the shear strength properties of soil material, or of discontinuities in soil or rock masses. The U.S. and U.K. standards defining how the test should be performed are ASTM D 3080 respectively.
UNCONFINED COMPRESSION STRENGTH TEST
The primary purpose of this test is to determine the unconfined compressive strength, which is then used to calculate the unconsolidated undrained shear strength of the clay under unconfined conditions. According to the ASTM standard D2166, the unconfined compressive strength is defined as the compressive stress at which an unconfined cylindrical specimen of soil will fail in a simple compression test. In addition, in this test method, the unconfined compressive strength is taken as the maximum load attained per unit area, or the load per unit area at 15% axial strain, whichever occurs first during the performance of a test.
CONSOLIDATION TEST
This test is performed to determine the magnitude and rate of volume decrease that a laterally confined soil specimen undergoes when subjected to different vertical pressures. From the measured data, the consolidation curve (pressure-void ratio relationship) can be plotted. This data is useful in determining the compression index, the recompression index and the pre-consolidation pressure (or maximum past pressure) of the soil. In addition, the data obtained can also be used to determine the coefficient of consolidation and the coefficient of secondary compression of the soil. ASTM D 2435 – Standard Test Method for One-Dimensional Consolidation Properties of Soils.