Influence of Intermediate Principal Stress on the Strength and Dilatancy Behavior of Rockfill Material: Fid-Bau Portal

Influence of Intermediate Principal Stress on the Strength and Dilatancy Behavior of Rockfill Material

Xiao, Yang / Liu, Hanlong / Chen, Yumin / Chu, Jian

Abstract

The mechanical behaviors of rockfill materials at a comparatively low pressure are very important (e.g., for the stability of the top part and the slope of rockfill dams). In addition, the stress conditions of rockfill dams are unlikely to be axisymmetric but are three-dimensional. Because of this, the influence of the intermediate principal stress has to be taken into consideration in design. This paper presents a study on the effect of intermediate principal stress on the strength and dilatancy behavior of rockfill material at a comparatively low pressure. A series of constant $b -value$ tests were carried out on rockfill materials commonly used for earth dam construction. Using the test data, the influences of the $b -value$ on the peak friction angle, critical-state friction angle, and maximum dilatancy angle of rockfill materials were investigated. A revised relative dilatancy index was proposed for rockfill material to describe the change in the shear strength with the intermediate principal stress. The relationship among the incremental friction angle, the maximum dilatancy angle, and the $b -value$ was examined. A linear relationship between the incremental friction angle and the revised relative dilatancy index was established by considering the effect of the $b -value$ . The predictions given by this relationship agree well with experimental data. Furthermore, the $b -value$ can influence the particle breakage of rockfill materials, indicating that such breakage is dependent on the stress path.