Soil mechanics - Lab Report Example

n-drained and drained were undertaken on the undisturbed soil samples to determine the shear strength parameters under drained and drained condition for the given soil sample from where the building will be constructed. Basing on the results, it is evident that the bearing capacity of the silt soil was much less as compared to the cohesion less soil ultimate bearing capacity. In this regard, the building codes permit higher bearing pressure for less cohesion soils like sand as compared to that of plastic soil (silt).

Tri-axial tests are laboratory testing techniques mostly applied to obtain shear strength parameters for different types of soil under un-drained and drained condition (Alshibli and Sture 2000). Conventional test entails a cylindrical soil sample which is subjected to radial stresses as well as axial displacement or controlled increases in axial stresses. Usually, the cylindrical soil specimen is of 200m height and 100 mm diameter. Preparation of specimen is based on the type of soil. For shear failure, the soil grains usually slide over each other along the failure surface hence there is no crushing of grains.

At failure, along the failure surface, the shear stress reaches the shear strength. Basically, soils are known to be frictional materials. The strength is based on the stress applied whereby this stress is controlled by effective stresses and here water pressure is needed (Alshibli and Sture 2000). Also soil strength is based on drainage whereby different strengths can be measured for a certain soil that can deform at a given constant volume (un-drained) as well as deform without having pore pressure that is excess (drained).

Angle of friction (ø) and Cohesion (c) are generally not soil constant parameters. They are based on the soil initial state and the loading type (drained or un-drained) (Widulinski et al., 2009). The specimen was enclosed vertically with a thin rubber membrane then later put between two rigid ends in the pressure