论文部分内容阅读
流变对工程岩体的长期变形稳定具有十分重要的影响,但目前关于卸荷流变的试验研究中通常只考虑恒轴压卸围压的应力路径,与隧洞开挖过程中围岩的应力调整过程存在一定的差距。以砂质泥岩为试验研究对象,设计进行了加轴压卸围压和恒轴压卸围压条件下的分级卸荷流变试验。试验结果表明:恒轴压卸围压和加轴压卸围压方案下岩样的流变变形趋势总体一致,但相同初始围压条件下,加轴压卸围压试样破坏的围压相对较高,偏应力相对较大,但长期强度与破坏应力的比值相对较小;在围压卸载至岩样临近破坏时,加轴压卸围压方案下岩样的流变应变增长速率明显较快,试样破坏的更加突然;恒轴压卸围压条件下岩样的破坏形态相对简单,一般只存在一条完整的剪切破坏面,而加轴压卸围压条件下岩样的破坏形态要复杂得多,除了控制性的剪切破坏面之外,还伴随有一定数量的次生剪裂纹和张拉裂纹,而且初始围压越大,试样的次生裂纹越多。因此,在隧洞围岩长期变形稳定分析过程中,单纯的恒轴压卸围压流变试验不能满足工程实际需求,应该尽量丰富岩石力学试验的应力路径,以便较好地模拟工程岩体应力的实际变化过程,研究成果为隧洞围岩的长期变形稳定性研究提供了较好的研究思路。
Rheology has a very important influence on long-term deformation and stability of engineering rock mass. However, the current stress-strain path of unloading and confining pressure is usually only considered in the experimental study of unloading rheology, which is consistent with the stress of surrounding rock during tunnel excavation Adjustment process there is a certain gap. Taking sandy mudstone as the research object, the graded unloading rheological tests were designed and carried out under the confining pressures of unloading and unloading under constant pressure. The experimental results show that the rheological deformation trend of rock samples under constant pressure unloading and axial pressure unloading is the same, but under the same initial pressure, But the ratio of long-term strength to failure stress is relatively small. When the confining pressure is unloaded to the vicinity of the rock specimen, the rate of rheological strain growth of rock specimens under pressure plus confining pressure is significantly higher The damage of the sample is more sudden. The failure mode of the rock specimen under the condition of the constant pressure and unloading confining pressure is relatively simple. Generally, there is only one complete shear failure surface, It is much more complicated, besides the controlled shear failure surface, a certain number of secondary shearing cracks and tension cracks are accompanied with the larger initial confining pressure, and the more secondary cracks in the specimen. Therefore, during the long-term stability analysis of the surrounding rock of tunnel, the pure constant-pressure unloading confining pressure rheological test can not meet the actual needs of the project. The stress path of the rock mechanics test should be enriched as much as possible in order to better simulate the stress of the rock mass The actual change process, the research results provide a good research idea for the long-term deformation stability of the tunnel surrounding rock.