盐岩的压剪疲劳特性与位错损伤研究

 开展不同剪切角度的压剪试验和疲劳试验，研究压剪作用下盐岩的力学特性和晶体位错特性，基于损伤力学观点，建立以位错为量度指标的损伤关系模型。得到的主要结论有：(1) 大于45度角剪切时，盐岩晶体位错的滑滞阻力较小，盐岩抗变形能力、峰值应力和最大变形量均随着剪切角度的增大而减小。裂纹以剪切面附近扇形裂纹发育为主；(2) 疲劳寿命和循环荷载的上限应力水平相关。剪切角度不同时，若应力水平相同，则其疲劳寿命(循环数)基本相同；若应力大小相同，则剪切角度越大，疲劳寿命越短。(3) 变向剪切对盐岩的疲劳寿命影响巨大，使疲劳寿命下降90%以上。(4) 盐岩疲劳裂纹的成核和位错的不断挤入挤出有关，裂纹扩展是多滑移系交替滑移的结果。建立了基于位错理论的盐岩损伤模型，使损伤能从本质上表达盐岩的破坏过程。越大的疲劳损伤使盐岩的承载能力下降越明显。

RESEARCH ON SALT ROCK COMPRESSION-SHEAR FATIGUE PROPERTIES AND DISLOCATION DAMAGE

We carry out different angle shear tests and fatigue tests，to research salt rock compression-shear mechanical properties and crystal dislocations characteristics. Based on the damage mechanics theory，dislocation-damage relationship model is established. The main conclusions are：(1) Because that salt rock crystal dislocation slip resistance decreases，salt rock deformation resistance，peak stress and maximum deformation decrease with increasing shear deformation angle. (2) Fatigue life is associated with cyclic stress limit level. At different shear angles，if stress level is the same，the fatigue life is substantially the same. If the stress value is the same，the greater the angle，the shorter fatigue life. (3) Reverse shear influences hugely the fatigue life of rock salt，with more than 90% decrease. (4) Salt rock fatigue crack formation is related with movement of dislocations squeeze. Crack growth is the result of alternating slippage for multiple slip systems. The dislocation-damage model is established，so that the damage can essentially reveal the destruction process of salt rock. The greater the fatigue damage results in more obvious decrease of the carrying capacity.