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为探究盐岩的应变硬化自弱化现象及机制,拟通过单轴压缩卸载、静置、二次加载试验来研究盐岩自弱化后强度指标和变形指标的变化规律。并基于位错理论,对自弱化的微观机制进行阐述。研究结果表明:(1)盐岩自弱化后的强度和弹性模量随静置时间(弱化时间)的变长而呈现弱化趋势;且4 h之前弱化趋势明显,之后趋势特征不明显。(2)盐岩弱化后的泊松比和等容变形率在4 h前后有台阶特征。泊松比的前台阶值小于后台阶值,等容变形率的前台阶值大于后台阶值。(3)盐岩自弱化现象是应变硬化后位错在内部残余应力(摩擦力和位错弹性力)的作用下逐渐远离集中区,均匀化的结果。
In order to explore the phenomenon of self-degeneration and mechanism of strain hardening of salt rock, uniaxial compression unloading, static load and secondary loading test are to be used to study the variation law of strength and deformation index of salt rock after weakened. Based on dislocation theory, the micro-mechanism of self-weakening is expounded. The results show that: (1) The strength and elastic modulus of the rock salt after weakened gradually weakened with the increase of the settling time (weakened time); and the weakening tendency is evident 4 h before, and the trend characteristics are not obvious afterwards. (2) The Poisson’s ratio and the isotropic deformation rate after salt rock weakened have a step feature around 4 h. Poisson’s ratio is less than the value of the front of the step after the step value, the equivalent deformation rate of the front step is greater than the value of the back step. (3) The self-weakening phenomenon of salt rock is the result of dislocation gradually getting away from the concentration zone and homogenizing under the effect of internal residual stress (frictional force and dislocation elastic force) after strain hardening.