剪切作用下土石混合料的颗粒破碎演化规律

Evolution of Particle Breakage of Soil-rock Mixture under Shearing

研究目的:铁路、机场、公路等路基填方中的土石混合料在一定应力条件下会发生颗粒破碎,从而造成相应的填方工程产生变形和稳定性问题。已有研究大多关注剪切破坏后的颗粒破碎特征,而对剪切过程中的颗粒破碎演化规律研究较少。针对该问题,本文采用配备声发射采集系统的大型直剪试验机分别对6种含石量和3种块石强度的土石混合料开展6种法向压力下的剪切试验研究。研究结论:(1)剪切完成后的AE总计数与颗粒相对破碎率呈线性增长关系,证明声发射技术在土石混合料颗粒破碎演化规律的研究中是可行的;(2)土石混合料在剪切过程中的颗粒破碎先后经历无破碎阶段、初始破碎阶段、破碎增长阶段、破碎稳定阶段、残余破碎阶段5个典型演化阶段,相应的应力应变状态分别进入弹性阶段、弹塑性过渡阶段、弹塑性阶段、峰值强度阶段和塑性破坏阶段;(3)当法向压力增大、或含石量升高、或块石强度降低时,无破碎阶段和残余破碎阶段持续时间越短,初始破碎阶段、破碎增长阶段、破碎稳定阶段总持续时间越长;(4)土石混合料和岩体在剪切过程中的声发射特征差别显著,根本原因是物质组成的连续性不同;(5)本研究结果可为土石混合料颗粒破碎问题的研究提供新思路。

Research purposes:Under certain stress conditions,the particles of soil-rock mixture in subgrade fillings of railway,airport,highway will be broken,which leads to the deformation and stability problems of the filling engineering.Most of the existing researches focus on the characteristics of particle breakage after shear failure,but few on the dynamic evolution of particle breakage during the shearing process.Therefore,a large-scale direct shear test machine combined with acoustic emission acquisition system was used to conduct shear tests on soil-rock mixtures with six rock contents and three rock strength under six normal pressures in this paper.Research conclusions:(1)The relationship between cumulative AE counts and relative breakage index of the failure soil-rock mixture is linear,which proves that it is feasible to use acoustic emission technology in the study of particle breakage evolution of soil-rock mixture.(2)The particle breakage stage during the shearing process can be divided into five typical stages:no breakage stage,initial breakage stage,growth breakage stage,stable breakage stage and residual breakage stage.The corresponding response of stress and strain enters the elastic stage,elastoplastic transition stage,elastic-plastic stage,peak strength stage and plastic failure stage.(3)When the normal pressure is greater,or the rock content is greater,or the rock strength is lower,the duration of the no breakage stage and the residual breakage stage become shorter,and the duration of the initial breakage stage,growth breakage stage,and stable breakage stage get longer.(4)The difference of acoustic emission characteristics between soil-rock mixture and rock mass during shearing process is significant,which is due to the different continuity of material composition.(5)The research results can provide a new idea for the study of particle breakage of soil-rock mixture.