初始固结应力对平面应变黄土剪切破坏特性影响

Effect of initial solidification stress on shear failure characteristics of loess under the plane strain condition

针对黄土工程中大量存在的平面应变问题,在均压固结条件下研究的较多,但与土实际的应力状态不符,利用平面应变改造后的真三轴仪,模拟土体的实际应力状态,通过原状黄土在不同初始固结应力比、含水率和围压条件下的竖向加载平面应变试验,揭示不同初始固结应力比、含水率和围压对原状黄土强度特性影响及破坏时中主应力变化规律。研究结果表明:偏压固结原状黄土的强度随着初始固结应力比的增大而增大,且明显大于均压固结;抗剪强度及破坏时p、q随着初始固结应力比的减小或含水率的增大而减小;土体原生结构损伤程度随着初始固结应力比的增大而增大使得黏聚力减小;当次生结构形成土颗粒间挤密使得内摩擦角增大;破坏时刻的中主应力随初始固结应力比增大而增大;破坏时刻的中主应力系数范围在0.15~0.45之间;平面应变条件下原状黄土破坏时的固结围压及含水率对中主应力系数的影响较明显。研究结果对进一步完善原状黄土的平面应变试验研究,进而解决平面应变条件下的黄土工程建设问题,提供试验依据和理论基础。

In view of the large number of plane strain problems in loess engineering,more studies have been carried out under the condition of isotropic consolidation,but it is not consistent with the actual stress state of the soil.The true tri-axial apparatus after plane strain modification is used to simulate the actual stress state of the soil.Through the initial loading plane strain tests under different initial consolidation stress ratios,moisture content and confining pressure of the original loess,different initial consolidations are revealed.The influence of initial consolidation stress ratio,water content and confining pressure on the strength characteristics of intact loess is discussed and the change law of intermediate principal stresses during failure are summarized.The results show that the strength of intact loess under anisotropic consolidation increases with the increasing initial consolidation stress ratio,and is significantly greater than that of equalized consolidation.The strength of intact loess increases with the increasing initial consolidation stress ratio,and is significantly greater than the isotropic consolidation.The shear strength and the p and q at failure decrease with the initial consolidation stress ratio.The decrease of water content increases,and the degree of damage to the primary structure of the soil increases with the increasing initial consolidation stress ratio,which reduces the cohesion.When the secondary structure forms the compaction of soil particles,the internal friction angle increases.The intermediate principal stress at the time of failure increases with the increasing initial consolidation stress ratio.The intermediate principal stress coefficient at the time of failure ranges from 0.15 to 0.45.The effect of consolidation confining pressure and water content of the intact loess under the plane strain conditions on the intermediate principal stress coefficient is obvious.The research results will further improve the plane strain test research of intact loess,and can solve the problem of loess engineering construction under the plane strain conditions,and also provide test basis and theoretical basis.