考虑局部含水率效应的浅层土体开裂过程与力学机制分析

Analysis of cracking process and mechanical mechanism of shallow soil due to local water content change

裂隙的产生和发育会极大地影响土体的强度、变形和渗透特性,进而引发各种工程灾害。为了进一步探究土体开裂过程和裂隙的发育规律,试验对土体开裂前、开裂初期以及开裂中后期的局部含水率进行测试。结合土体随含水率变化的横向收缩特征,分析裂隙过程的力学机制,建立适用于浅层土体开裂全过程的定量化计算和判别公式。研究发现:土体在开裂前后的竖向含水率分布随着土体深度的增加而逐渐线性递增,其累计横向收缩率随含水率的下降而逐渐增大;通过浅层土体的表层含水率和土体深度,可以推导出适用于浅层土体的抗拉强度和张拉应力表达式,进而对浅层土体开裂的3个典型阶段进行定量化描述;在裂隙发育的初期,新裂隙的产生会导致土体张拉应力降低,将裂隙总长度、平均宽度、裂隙度等基本指标与张拉应力建立联系,能够清晰地对开裂初期的复杂变化过程进行解释和描述。此外,结合土体的初始缺陷、裂隙边缘的应力集中等特征,对裂隙发育过程进行了深入地分析讨论。

The initiation and propagation of cracks will greatly affect the strength,deformation and permeability of soil,and then lead to various engineering disasters.In order to further explore the crack initiation and propagation mechanism of soil,the local water contents in three stages were measured.Besides,the lateral shrinkage characteristics of soil were also tested with the change of water content.The mechanical mechanism of the cracking process was analyzed,and the quantitative calculation and discriminant formulas for the whole cracking process of shallow soil were established.The results show that the vertical water content distribution increases linearly with the increase of soil depth during the first two cracking stages,and the cumulative horizontal shrinkage increases with the decrease of water content.Based on the surface water content and depth of shallow soil,the mathematical expressions of tensile strength and tensile stress for shallow soil can be deduced,and then the three typical cracking stages of shallow soil can be analyzed.At the early stage of cracking,the generation of new cracks leads to the decrease of tensile stress on the soil surface.The basic indicators such as total crack length,and the average width and degree of cracks,are related to tensile stress.The correlations between tensile stress and crack indicators could explain and describe the complex change process clearly in the initial stage of cracking.Moreover,combined with the initial defects of soil and the stress concentration at the crack edge,the cracking process was further analyzed and discussed.