围压和密度对粗粒料临界状态力学特性的影响

粗粒料的力学特性不仅取决于有效围压,还与密实程度密切相关。通过4组不同初始干密度粗粒料的大型三轴固结排水剪切试验,研究了围压和密度对粗粒料临界状态力学特性的影响。试验结果表明:软化型应力应变曲线破坏状态偏应力大于相变状态偏应力,而相变状态偏应力与临界状态偏应力较为接近;不同围压、不同密度的试验,随着剪切的进行,偏应力与平均正应力的应力比逐渐趋向于临界应力比,软化型试验应力比曲线呈单驼峰型形态,硬化型试验应力比曲线呈爬升型形态;临界孔隙比随临界平均正应力的增大而减小,随初始孔隙比的增大基本呈线性增大。研究成果可为特征状态参数研究和临界状态本构模型的建立提供依据。

Effects of Confining Pressure and Density on Mechanical Properties of Coarse Granular Material under Critical State

The mechanical properties of coarse granular material are not only depending on effective confining pressure, but also closely related to compaction degree. The effects of confining pressure and density on mechanical properties of coarse granular material under critical state were investigated using large-scale triaxial consolidation and drainage shear tests on specimens with four different initial dry densities. The deviatoric stress at failure state for softening stress-strain curve is larger than that at phase transformation state which is closer to the deviatoric stress at critical state. The stress ratio of deviatoric stress to mean normal stress gradually approaches the stress ratio at critical state. The curve of stress ratio for softening stress-strain test displays a single hump shape, while the curve of stress ratio for hardening stress-strain test shows a climbing shape. The critical void ratio decreases with the increase of mean normal stress under critical state, and basically increases linearly with the increase of initial void ratio.