Evaluation of soil shear strength parameters via triaxial testing by height versus diameter ratio of sample

The triaxial test is a most widely used laboratory method for determining the soil shear strength. It is assumed that a soil sample deforms uniformly during triaxial testing. But one often faces a case when the sample in the triaxial apparatus deforms on the contrary. The non-uniformity can be caused by the end restraining effect, the sample height influence factor, the insufficient drainage, the membrane effect and the sample self-weight factor etc. An analysis of known investigations lead to the following tools that could be employed for reducing an inaccuracy related to the non-uniform stress-strain distribution per soil sample during triaxial testing: reducing the sample height/diameter ratio from 2 to 1, eliminating the friction between the sample ends and the plates. Having not eliminated the above - mentioned influence, factors during the testing procedure the angle of internal friction φ and the cohesion c for the sample of φ ≠ 0 are determined larger than the actual ones. The method for determining the angle of internal friction φ and the cohesion c, when testing the soil sample of height/diameter H/D = 1 is proposed.