卸围压条件下砂岩变形破坏特性试验研究

Experimental study on deformation failure of sandstone under unloading confining pressure condition

从可释放弹性应变能角度对岩石卸围压条件下破坏特性进行研究,利用MTS815电液压伺服可控制刚性试验机进行保持轴向变形不变的卸围压试验,根据卸围压试验数据,分析了该砂岩卸围压过程中变形、强度、弹性模量及能量变化特征。结果表明:随着围压逐渐降低,岩样发生侧向不断扩容;轴向应力逐渐降低,呈现出非线性特征;弹性模量在初始阶段几乎不变化,越过破坏点之后大幅降低;可释放的弹性应变能在初始阶段增大比较缓慢,当围压降低至一定程度时急剧增大;推导出基于可释放弹性应变能的卸荷岩石的整体破坏准则Ue0。

Study failure characteristic of rocks under unloading confining pressure conditions from the released elastic strain energy is of great significance. Firstly, unloading confining pressure test maintai- ning constant axial deformation was carried out by using MTS815 electric hydraulic servo control test- er. Secondly ,the sandstone deformation, strength, elastic modulus, and energy variation during unloa- ding confining pressure were analyzed by according to unloading confining pressure test data. The re- sults show that with the confining pressure decreases, rock samples occur laterally continuous expan- sion; modulus of elasticity almost no change in the initial stages and significantly lower after crossed the failure point; axial stress decreases, showing a non -linear characteristic, releasable elastic strain energy increases more slowly in the initial stage, when the confining pressure reduced to a certain ex- tent increases rapidly. Finally, based on the release of elastic strain energy theory deduce the failure criterion of rock unloading confining pressure. The whole failure criterion of loading rock under unloa- ding confining pressure, which was U0e, was concluded.