The use of undrained triaxial test - Lab Report Example

The graph for normal stress against a shear stress is gives a straight line from the origin. This insinuates that for both shear stresses, an increase in normal pressure applied leads to increase in shear stress. Further, from the graph it is obvious that shear strength yields a greater frictional angle and failure envelope than that for the residual strength as expected for soils.With application of the masses, shear stress initially increased rapidly upto a certain point, after-which the increase reduced.

Generally, this shows that with increasing loads, the shear stresses also increase. As shown in the graph, there is a strong positive increase observed in the value of shear strength upto the peak point where the slope starts to decrease into a shallow gradient. It is at this point that the residual stress is observed. The range for effective angles of friction range between 35 degrees for dense sands and 27 degrees for loose sands (Helwany, 2007, 107). Our results fall into these values that gives a medium density outcome for our sample.

Consequently, the results are in line with the expectations that the peak strength should be greater than residual strength of the soil.Even though the experiment was successful in meeting its objective, there might have been sources of errors leading to slight deviations witnessed. Most obvious source is human errors arising when taking the readings from the instruments used. Further, there might have been mistakes when setting up the apparatus such as the shear box.