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为了研究复杂应力环境下岩体工程开挖的影响,设计内压加卸载试验装置,利用内径20 mm、外径49.84 mm的厚壁圆筒石灰岩试样,在RMT–150C岩石力学试验系统进行不同内压条件下的加卸载试验,重点分析了孔内卸压条件下试样的破坏形式产生机制。结果表明:(1)固定孔压加载时,由于试样孔道内外存在应力差,不能进入延性变形阶段,高围压时有孔压试样的强度明显高于无孔压试样的强度;(2)孔压卸载对试样造成的损伤较大,卸载孔压后重新加载的试样,其强度低于常规三轴压缩时的孔道试样;卸载破坏时试样内外压差越大,其强度越小,表明围岩发生破坏的根源在于巷道开挖卸载后引起应力差的增加;(3)固定孔压时,试样多呈现单一的剪切面滑移破坏,而卸载孔压时试样破坏形式都为张拉破坏或者压拉组合破坏,应力路径对孔道试样破坏形式影响较大。研究结果为揭示深埋巷道围岩破坏失稳现象的产生机制提供参考。
In order to study the influence of excavation in rock mass engineering under complex stress environment, an internal pressure loading and unloading test device was designed. Based on the RMT-150C rock mechanics test system, a thick cylindrical limestone sample with an inner diameter of 20 mm and an outer diameter of 49.84 mm was used Under the conditions of internal pressure loading and unloading test, focusing on the analysis of the hole under the conditions of pressure relief sample form mechanism. The results show that: (1) Because of the stress difference inside and outside of the sample hole, it can not enter the ductile deformation stage when the fixed pore is loaded with pressure. The strength of the porous specimen with high confining pressure is obviously higher than that of the non-porous specimen. 2) The hole pressure unloading is more damaging to the sample, the sample reloaded after unloading the hole pressure is lower than the hole sample in the conventional triaxial compression. The greater the pressure difference between inside and outside of the sample when the unloading is damaged, The smaller the strength, the more the root cause of the failure of surrounding rock is the increase of stress difference caused by unloading of roadway excavation. (3) When the fixed pore pressure is applied, the specimens show a single shear surface slip failure, The damage forms are both tensile failure and compression-combined failure, and the stress path has a greater impact on the damage form of the pore samples. The results provide a reference for revealing the mechanism of rock failure and instability in deep roadways.