One-dimensional stress relaxation of cohesive soils and its relationship with secondary compression

The behaviors of one-dimensional relaxation have been studied by many researchers. However, the method for deducing the stress relax formulas is usually complicated. Two simple stress relaxation formulas in single-logarithmic form and double-logarithmic form are derived, which are based on the Buisman secondary compression equation and the concept of the equal-time compression line proposed by Bjerrum. The relationships between the slopes of these two types of stress relaxation formulas and the parameter c_a/c_c are proposed, here c_a is the secondary compression index and c_c is the compression index. One-dimensional secondary compression and the stress relaxation tests using Shanghai clay are conducted. The reliability of the stress relaxation formulas is verified. Moreover, the one-dimensional stress relaxing rate of general cohesive soils is estimated according to the values of c_a/c_c proposed by Mesri and Godlewski.