摘要
为探究砂土形状对剪切失稳特性的影响,首先通过显微图像采集与处理技术,对相同粒径和级配、不同形状的石英砂进行了颗粒形状分析;然后在应力控制条件下进行了不排水三轴剪切试验,建立了基于应变速率增量(ΔSR)的石英砂失稳判据;最后通过PFC2D模拟了不同形状颗粒柱的坍塌试验并对失稳机理进行了探讨。结果表明:ΔSR可作为一种新手段判别砂土是否发生失稳;形状规则砂样会出现“假失稳点”,且峰值点也是失稳点,而形状不规则砂样的峰值点滞后于失稳点;在应力控制条件下,形状规则砂样的应力路径呈“锯齿状”发展、超静孔隙水压力和轴向应变呈“阶梯式”发展,而形状不规则砂样的试验曲线未出现突变;不同形状砂样在失稳时表现出的差异与颗粒间的能量转换机制以及接触运动形式有关。研究成果可为边坡的稳定分析以及滑坡等地质灾害的预防提供参考。
In order to investigate the influence of particle shape on the shear instability characteristics of sand,the particle shape analysis of quartz sand with the same gain size and gradation,but with different shape was firstly made by using the microscopic image acquisition and processing techniques.Then the undrained triaxial shear tests were conducted under stress controlled condition,with a instability criterion established based on the strain rate increment(ΔSR).Finally,the collapse tests of granular columns with different particle shape were simulated by PFC2D and the mechanism of destabilization was examined.The results show thatΔSR can be used as a new means to determine whether the sand is instable or not.When the value ofΔSR is continuously shaken,the sample has a large cumulative deformation,and the sample becomes instable.The instability point is also the peak point in the sand samples with regular particle shape.And the samples exhibit a“false instability point”,which shows that the shear stress of the samples decreases and increases suddenly with the development of strain during the shear process.On the other hand,the peak point of the irregularly-shaped sand samples lagged behind the instability point.Under stress controlled condition,the stress path of the regular-shaped sand samples is in a“jagged”pattern,and the excess pore pressure and axial strain are in“stepped”patterns,but the test curves of the irregular sand samples do not show any sudden changes.The difference of instability of sand samples with different shapes is related to the energy conversion mechanism and contact motion formed between particles.The research results could provide a reference for slope stability analysis and a guidance for prevention of geological disasters such as landslides.
作者
刘鑫
徐新钰
黄良
钟源
LIU Xin;XU Xinyu;HUANG Liang;ZHONG Yuan(School of Geological Engineering and Geomatics,Chang’an University,Xi’an 710054,China;School of Engineering,China University of Geosciences,Wuhan 430074,China;China West Airport Group Co.,Ltd.,Xi’an 710075,China)
出处
《西安科技大学学报》
CAS
北大核心
2024年第3期532-542,共11页
Journal of Xi’an University of Science and Technology
基金
国家自然科学基金项目(41927806,42041006)
陕西省自然科学基础研究计划项目(2022JQ-251)。
关键词
砂
颗粒形状
失稳
应力控制
三轴试验
sand
particle shape
instability
stress control
triaxial test
