Abstract:

A series of true triaxial consolidation and drainage shear tests were conducted on a typical dam-building rockfill. These tests followed constant p-value and b-value stress paths. The purpose was to investigate the effects of spherical stress p, the coefficient of intermediate principal stress b and the initial dry density on various aspects. These aspects include the generalized stress-strain relationship, dilatancy, strength properties, and noncoaxiality of the stress-strain increment direction on the π-plane of the rockfill. The applicability of different strength criteria to the rockfill material's strength was compared and analyzed based on the measured test data. This analysis considered the influence of the intermediate principal stress.Results indicate that with increasing spherical stress and initial dry density, the initial shear modulus E_i and the peak strength q_max of the rockfill material gradually increases. An increase in spherical stress p suppresses the dilatancy characteristics. When the initial dry density is high, the sample is more likely to enter a dilatant state. As the intermediate principal stress coefficient b increases, the peak strength q_max gradually decreases, and the dilatancy characteristics become more obvious.The Lade-Duncan strength criterion can reasonably describe the nonlinear strength characteristics of the rockfill material and better characterize its nonlinear strength properties. In the initial shear phase, the sample exhibits the highest non-coaxiality, which diminishes as the sample approaches failure, with stress-strain increments tending towards coaxiality. Non-coaxiality first increases and then decreases with larger b values, weakens with higher p, and strengthens with greater ρ₀.

Key words: rockfill, true triaxial test, stress-strain relationship, dilatancy, non-coaxiality