峰前卸荷对节理岩体力学特性影响试验研究

Experimental research on mechanical property of jointed rock mass unloading before peak

实际工程中,岩体的应力变化状态非常复杂,并不只是简单的加载或者卸荷,如水利工程中的大坝,当坝基开挖时其力学条件主要表现为开挖方向的卸荷(其他方向有可能卸荷,也有可能加载),而坝体修筑以后,力学条件又主要表现为加载。因此,对卸荷损伤后的岩体再次加载时的力学性质进行研究具有十分重要的工程意义。通过三轴卸荷及卸荷损伤后加载破坏试验,研究了不同围压下,含断续预制节理岩体经过不同程度卸荷损伤后再次加载时的力学特性。研究结果表明:围压对于含断续节理岩体变形模量影响不明显,岩体弹性模量与围压没有明显关系,相同围压下节理岩体弹性模量和变形模量均显著低于完整岩体:节理岩样峰值应变随着围压的增大线性增大,二者之间有较好的相关性,相比于完整岩样,节理岩体峰值应变随围压增大增长更快:围压越低,卸荷对岩体强度的影响越大,随着围压增加,卸荷量不同造成岩样的损伤差异逐渐减小。

The stress state of rock mass is very complex in practical engineering; it＇s not just a simple loading or unloading; such as the dams of hydraulic engineering, considering from its mechanical condition, the dam foundation excavation main shows the unloading at the direction of excavation （other directions may be unloading or loading）; after construction of the dam , it main shows loading from the mechanical condition, so it has an important engineering significance to study the mechanical properties of rbck mass＇ reloading after a unloading damage. The results show that： the confining pressure for intermittent jointed rock deformation modulus has little effect; the elastic modulus of rock has no apparent relationship with the confining pressure; jointed rock mass deformation modulus and elastic modulus are significantly lower than intact rock under the same confining pressure： jointed rock peak strain increases linearly with the confining pressure; and there is a good correlation between the two. Compared to the intact rock samples, joint rock the peak strain of jointed rock grows faster with confining pressure increasing. The lower the confining pressure is, the greater of the impact of unloading on rock strength is. With confining pressure increasing, different of damage caused by different unloading amount of rock samples will decrease.