考虑应力路径和颗粒破碎影响的钙质砂剪胀特性及剪胀方程研究
Dilatancy behaviors and equation of calcareous sand considering stress path and particle breakage
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摘要: 钙质砂的剪胀特性受应力路径和颗粒破碎的共同影响。为了探讨钙质砂在不同应力路径下的剪胀特性,进行了一系列不同固结压力和应力路径组合的排水三轴压缩试验。结果表明:应力路径和颗粒破碎对钙质砂的剪胀特性有重要影响。不同应力路径下钙质砂的剪胀比与应力比的关系存在显著差异。相同应力比下的剪胀比,等围压试验的最大,等轴向应力试验的最小,等平均主应力试验的居中。峰值应力比对应的剪胀比随峰值应力比的增大而减小且为线性关系,随颗粒相对破碎率的增大而增大并近似呈幂函数关系,应力路径对这些关系的影响不大。忽略应变软化阶段的剪胀比与应力比相关的参数大致呈线性关系,其直线斜率与应力路径和固结压力相关。基于试验结果,提出了一种与应力路径和颗粒破碎相关的剪胀方程并进行了试验验证,显示出剪胀方程对不同类型的粒状土均具有较好的适应性。Abstract: The stress path and particle breakage have an impact on the dilatancy of calcareous sand. A series of drained triaxial compression tests with different stress paths and confining pressures are carried out to investigate the dilatancy of calcareous sand. The results show that the stress path and particle breakage have important effects on the dilatancy of calcareous sand. The relationship between the dilatancy ratio and the stress ratio of calcareous sand under different stress paths is significantly different. Under the same stress ratio, the dilatancy ratio in the constant confining pressure tests is the maximum, and that in the constant axial stress tests is the minimum. The dilatancy ratio in the constant average principal stress tests is between above two tests. The dilatancy ratio corresponding to the peak stress ratio decreases with an increase of the peak stress ratio, which follows a linear relationship, and increases with an increase of the relative breakage index, which is approximated by a power function. These relationships are not affected by the stress paths. The relation between the dilatancy ratio and the parameters related to stress ratio is linear under the condition of ignoring strain softening stage, and its slope is related to the stress path and the consolidation pressure. Based on the test results, a dilatancy equation related to the stress path and particle breakage is proposed and verified. It is shown that the dilatancy equation has better adaptability to different types of granular soils.