Soil Elastic Modulus Measurement Using Triaxial Test - Research Proposal Example

The basic concept applied in performing the triaxial shear test is that when stress is implemented in the vertical direction along the axis of a cylindrical sample the resulting stress is different from stresses applied in the horizontal direction perpendicular to the sides of the cylindrical sample (BISHOP and HENKEL, 1962, p.12).When performing the triaxial test on homogeneous and isotropic materials, it results in a non-hydrostatic stress state, with the shear stress on certain occasions leading to the failure of the sample in shear.

Inhomogeneous and anisotropic materials, the resulting shear stress may lead to failure due to the bending moments. There are various types of triaxial tests. They include Consolidated Drained (CD), consolidated undrained (CU), and unconsolidated undrained (UU).In CD, the sample is consolidated and shared while the compression results in drainage. In CU, the given sample is not allowed to drain and is compressed at a constant rate. In UU, the sample is not permitted to flow and is compressed at a constant rate (BISHOP and HENKEL, 1962, p.25).To perform the triaxial test on soil, a cylindrical soil sample is used.

The soil sample is confined to a rigid bottom and top plate that is covered by a rubber membrane. A vertical load is then placed on top of the sample. The horizontal pressure is then applied on the sides using water (Hydrostatic pressure). The rubber membrane is used to prevent water from penetrating. Throughout the experiment, the water pressure is constant. By increasing vertical pressure at a constant velocity, the soil sample gradually compresses until shearing occurs. From the triaxial test, the following shear strength parameters are derived.

They include the cohesion, angle of internal friction, and dilatancy angle. Rigid parameters such as the Young modulus of elasticity can also be determined (DONAGHE, CHANEY, and SILVER, 1988, p.6).