考虑级配和颗粒破碎影响的堆石料临界状态研究

临界状态土力学理论在描述细颗粒土应力变形特性方面较为成功,已经成为建立许多黏土和砂土本构模型的基础。对于堆石料,在应力、密度、级配等因素影响下,其变形特性非常复杂,且高应力条件下颗粒易发生破碎,是否存在"唯一"的临界状态值得探讨。通过对不同级配、不同密度的试样在不同围压条件下的一系列大型三轴剪切试验,研究了堆石料的临界状态及其影响因素。研究发现:不同级配、不同密度、不同初始固结应力条件下,当剪应变较大时试样都趋于临界状态,临界状态的值与初始密度、初始级配、颗粒破碎有关;q–p'平面内,堆石料存在唯一的临界应力比M;在e–(p'/p_a)~ζ平面内,临界状态线基本平行,其截距可以根据初始密度和初始级配直接求得。通过对比分析各试样的临界状态,提出了考虑级配和颗粒破碎影响的堆石料临界状态数学表达式。

Critical state of rockfill materials considering particle gradation and breakage

The theories of critical-state soil mechanics are satisfactory in describing the stress-strain characteristics of fine-particle soils and have become the foundation for establishing various constitutive models for clay and sandy soils. As for rockfill materials, under the influences of some factors such as stress, density and gradation, their deformation characteristics are very complex, and their particles are easily broken under high stress. Whether there exists the only critical state or not is worthy of being discussed. Through a series of large-scale triaxial shear tests on rockfill specimens with different gradations and densities under different confining pressures, the critical state of the rockfill materials and the influencing factors are investigated. The test results show that, under different gradations, densities and initial consolidation stresses, when the shear strain is large, the specimens all tend to be in the critical state, and the values of the critical state relate to the initial density, gradation and particle breakage. And in the - plane, there exits the only critical stress ratio M for rockfill materials. Then, in the - plane, the critical state lines are basically parallel, and their intercept can be directly obtained according to the initial density and gradation. A mathematical expression for the critical state of rockfill materials considering particle gradation and breakage is proposed by comparing and analyzing the critical states of various rockfill specimens.