Field Rebound and Recompression Curve of Soft Clay

Abstract

Abstract During sampling and sample preparation, the soil specimen is disturbed, which is accompanied by a decrease in void ratio, and the stresses within it release from in situ status to a residual one, usually associated with an expansion to some extent. As a result, the in situ void ratio and field recompression index, i.e., ev0 and CFR, change to e0 and CLR, respectively, which have not been properly accounted for in the traditional method. A rebound-recompression method (RRM) is proposed in this article for the derivation of a field compression curve from laboratory compression test results, with techniques being developed to modify these two parameters from laboratory measurements to field ones. This method has the clear advantage that the rebound and recompression behavior prior to the yield stress can be satisfactorily captured. Moreover, criterion to assess the sampling and preparation quality of soil samples is also proposed. This new method is validated against three consolidation tests with differing stress paths. In addition, measurements from an excavation in the field suggest that the RRM yields reliable results and highlight the nonconservativeness of the traditional method in deep excavation engineering.