Abstract: It is of important theoretical value and practical significance in geotechnical engineering to describe the lateral earth pressure coefficient at rest in overconsolidation stratum. In this study, based on the theoretical analysis evolution of lateral pressure at rest during overconsolidation, the excess lateral stress release characteristics of overconsolidated silty clay were investigated through confined rheological tests. The relationship between the residual excess lateral earth pressure and the overconsolidation ratio (OCR) was established, and a new method for calculating the at rest lateral earth pressure coefficient in overconsolidation stratum was proposed. The proposed method was validated by the in-situ KSB test and laboratory test, respectively. Moreover, the proposed method possessed clear physical meanings and achieved unification with empirical formulas under medium-high OCR levels. The results revealed that excess lateral earth pressure went through rebound process and relaxation process, and finally stabilized at residual excess lateral earth pressure . For silty clay, the release of excess lateral earth pressure mainly occurred during the rebound process. The ratio of residual value and initial value of excess lateral earth pressure increased with increased OCR, and no longer changed when OCR>OCRr. The conclusions could provide reference and basis for the calculation and numerical analysis of earth pressure of retaining structures in overconsolidation stratum.

Key words: earth pressure coefficient at rest, overconsolidation, silty clay, lateral stress relaxation, in-situ test