GEOLOGY LABORATORY
Geology laboratory maintains the ability to serve our client’s needs related to geotechnical engineering. Significant contributions to testing in recent year have been follow from International Standards (BS 1377: 1990).
 
Geology Laboratory has been associated and committed to supplying quality complying with test specifications. The satisfactory solution of problem with required the use of standard method by trained and qualified engineers and technicians.
GEOLOGY LABORATORY
SOIL INVESTIGATION
INSTRUMENTATION & MONITORING SECTION
 
   
 
MOISTURE CONTENT

A sample of soil is dried to constant dry weight at a temperature of 105 degrees centigrade and the moisture content determined.

SPECIFIC GRAVITY

The ratio of the unit weight of a material to the unit weight of distilled water at 4°C is a common definition of specific gravity. Soil specific gravities, however, are normally referred to the weight of water at 20°C. In itself, the specific gravity is not an index property of a soil. It is, however, required for determination of the unit weight of a soil and in many computations.

ATTERBERG LIMIT TESTS

This is a valuable classification test in which an arbitrary procedure is used to determine the moisture contents at which a soil changes from a liquid through a plastic to a solid state and gives an indication of the clay quantities present in the soil. The results are used to assess soil properties, swelling and shrinkage potential, frost succeptability and earthwork suitability.

PARTICLE SIZE ANALYSIS (SEIVE & HYDROMETER)

In this test a riffled sample of soil is washed over a series of sieves and the percentages passing each sieve are determined and shown graphically on grading charts. This provides a method of determining the proportions of coarse, medium and fine silt and clay in a soil sample. The rate of fall of particles in water are proportional to their diameters, and their specific gravity. The time intervals are selected such that all particles of a specified size (eg silt size) have fallen past the sampling depth. The mass of suspended matter in the samples is determined by weighing and is used to determine the percentage of soil in the specimen which is finer than the specified size. In this way, the percentage of silt and clay fractions is calculated.

 
 
 
CONSOLIDATION TEST

In this test a sample of 75 mm diameter and 20 mm thickness is subjected to a uniform load over its surface and the rate and amount of movement recorded. When movement has ceased, the load is increased and similar recordings are taken for a number of loads. The results are used in the estimation of magnitude and rate of settlement. Fine-grained soil is tested in long-term compression over two weeks to determine volume change behavior under load.

Over time, water pressure decreases and load is carried by the soil structure itself. When a saturated soil mass is subjected to an increase in load (such as a new building), it is carried initially by in creased pore water pressure. The resulting "excess hydro static pressure" causes water to drain from the soil pores, shifting the load to the soil structure.
   
 

The volume of the soil also decreases (equivalent to the volume of water drained) causing settlement. The process is known as consolidation. Three important soil properties found using a consolidation test are: The coefficient of consolidation, CV, obtained from deformation-time curve data and an equation. It indicates the rate of compression under a load increment. The pre-consolidation stress, s'p, obtained graphically from a log stress-void ratio curve. It indicates the maximum past effective stress the soil has been subjected to. The compression index, Cc, also obtained graphically from the log stress-void ratio curve. It indicates the compressibility of the specimen.

 

 
 

TRIAXIAL COMPRESSION TEST (UU)

The objective of the unconfined compression test is to determine the UU (unconsolidated, undrained) strength of a cohesive soil in an inexpensive manner. Shear characteristics of the soil are obtained by the undrained triaxial test. In this test, 38 mm diameter or 100 mm diameter samples were tested in compression under a series of varied lateral pressures, and the angle of shearing resistance and apparent cohesion obtained.

   
 


CONSOLIDATED UNDRAINED TRIAXIAL TEST

Fine-grained soil is tested in compression. Undisturbed specimens cut from tube samples and disturbed specimens are loaded in compression, recording load and deflection measurements. In this test a set of three 38 mm diameter samples are consolidated under the proposed cell pressure, with back pressure applied to ensure the samples are fully saturated.

 
               
 

SMALL SHEAR BOX TEST (DIRECT SHEAR TEST)

In this test normal stress is applied to a soil sample 60 x 60 x 20 mm in thickness and the sample is then sheared under a lateral stress. During the test the volume change occurring during shear, the peak shear stress, and the normal stress are obtained. Three tests are carried out, each under a different normal stress, and the failure envelope and shear strength parameters are determined.

   
     
   
   

POINT LOAD TEST

This test is an indirect method to determine compressive strength of a sample. The point load strength index, Is (50) by using correlation UCS = 20 X Is (50) to determine compressive strength. The sample can be categorised based on the point load strength index.
   
 
   
 
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