节理砂岩在循环加卸载下力学特性及损伤规律实验研究

Experimental Study of Mechanical Characteristics and Damage Law of Joint Sandstone Under Cyclic Loading and Unloading

为研究不同方向频繁扰动对节理岩体力学特性及损伤规律的影响,利用伺服试验机对南坡铜矿砂岩平行层理方向、垂直层理方向进行单轴循环加卸载,每次应力水平依次递增的实验,直至岩石破坏,通过实验数据分析得到:1平行层理方向加载的泊松比和弹性模量比垂直层理方向大,破坏强度相反;2卸载阶段的弹性模量和泊松比总比对应的加载阶段的要大;3随着循环次数的增加,两种加载方向均体现出形成的封闭塑性滞回环的面积逐渐增大,但垂直层理方向增加幅度要明显大于平行层理方向;且对应的各循环阶段的滞回环面积比平行层理方向要大;4每次循环残余变形量总比上一次的要大,但增长速度降低,降低幅度为5%~10%;5对于两种不同的加载方向,损伤规律、纵向应变的发展及应力大小有很好的一一对应关系,且岩石的损伤记忆性不受各向异性影响.

In order to study the influence of frequent disturbances in different directions on the mechanical characteristics and damage law of joint sandstone,uniaxial cyclic loading and unloading experiment is performed parallel and perpendicularly on the bedding planes of Nanpo copper mine＇s sandstone by servo testing machine. The stress level is incremental until the rock is destroyed. It is shown through the experimental data that： ①parallel Poisson＇s ratio and elastic modulus are larger than perpendicular ones while the failure strength is in reverse order; ② the elastic modulus and Poisson＇s ratio of unloading phase is larger than those of the corresponding loading phase; ③ with the increase of the number of cycles,a closed plastic hysteresis loop area is gradually increasing in both loading directions. The perpendicular increasing rate and hysteresis loop of each cycle phase are significantly larger; ④ residual deformation per cycle is larger than the last cycle,but with slower growth and the reduction being 4% to 10%; ⑤ in the two loading directions,the damage law,the development of longitudinal strain and stress have a good correspondence,and the damage memory of rock is not influenced by anisotropy.