A Simplified Direct Shear Testing Procedure to Evaluate Unsaturated Shear Strength

摘要

The work in this paper presents a simplified and expedient procedure to evaluate unsaturated shear strength using conventional direct shear testing with tensiometer-measured suctions. Two types of residual soils are utilized in this testing program. These are classified as elastic silt (MH) and silt (ML) and were obtained from a test site in Greensboro, North Carolina. Unsaturated triaxial tests were performed to provide reference values for comparison with the measured values from the proposed direct shear testing approach. Both single stage and multistage triaxial tests were performed, and an insignificant difference in the peak stress from both approaches was found. The total cohesion intercept was used to represent the strength contribution of the matric suction in order to normalize the effect of the confining pressure. The applicability of the simplified expedient procedure in assessing shear strength of residual soils used herein was demonstrated based on the total cohesion intercepts obtained from both testing approaches. The results from the proposed approach were very similar to those obtained from the unsaturated triaxial compression tests.