夹岩工程硬脆灰岩力学特征及数值试验研究

Study on mechanical characteristics and numerical experiment of hard brittle limestone for Jiayan Water Control Project

针对贵州省夹岩水利枢纽工程引水隧洞灰岩开展高围压三轴力学试验,结合声发射测试技术,探讨灰岩在达到峰值应力前的力学特性和裂纹发展规律,并利用自主开发的CASRock数值模拟软件进行了验证。试验结果表明:工程处灰岩在5~70 MPa围压作用下形成单一宏观剪切裂缝,无分支裂缝产生,峰后阶段具有明显的脆性特性,同时弹性模量和泊松比对围压不敏感;在压应力作用下声发射存在"平静期"和"活跃期",在临近峰值应力时声发射能量会出现加速释放现象。数值模拟结果与室内试验结果相一致,直观地展示了剪切裂纹扩展全过程。在此基础上,采用CASRock软件对夹岩工程隧洞进行了稳定性分析。研究结果对脆性岩体开挖支护设计具有一定的指导意义。

A high-confining pressure triaxial experiment is made on the limestone of the diversion tunnel of Jiayan Water Control Project in Guizhou Province, while the pre-peak mechanical characteristics and the cracking development law of the limestone are discussed in combination with the acoustic emission testing technique, for which the verification is carried out by means of the independently-developed numerical simulation software—CASRock. The experiment result shows that the sample of the limestone of the diversion tunnel for Jiayan Water Control Project forms a single macroscopic shearing crack under the effect of the confining pressure of 5~70 MPa without any branching fractures, which have an obvious brittle characteristics in the post-peak phase, while both the elastic modulus and Poissoni’s ratio are not sensitive to the confining pressure. Under the effect of compressive stress, both quiet period and active period are there for the acoustic emission signal and an accelerated releasing phenomenon of the acoustic emission energy is to occur near the peak stress. The numerical simulation results are consistent with those from the indoor experiment and visually exhibit the entire process of the development of the shearing crack. On the basis of this, a stability analysis is made on the diversion tunnel of Jiayan Water Control Project with the software—CASRock. The study result has a certain guiding significance for the excavation supporting for brittle rock mass.