为分析深埋隧道开挖过程中围岩破裂的尺寸、机制和过程,本文以西南某隧道为研究对象,在隧道中构建微震监测系统,采用双差定位确定隧道开挖过程中微震事件的空间位置,并对静态应力降、动态应力降、震源半径等震源参数的演化规律进行了研究。结果表明:(1)开挖过程中围岩的破坏形式以拉破坏为主;(2)的静态应力降与天然地震和矿山微震相比要小几个量级,表明在围岩应力调整相对较小,同时隧道的动态应力降要小于静态应力降,表明隧道围岩破裂程度较高;(3)震源破裂的尺寸要大于浅埋隧道,但是小于矿山微震和天然地震;(4)深埋隧道围岩的破裂过程与天然地震和矿山微震存在区别,在研究过程中既要借鉴天然地震和矿山微震方面的研究成果,又要注意其与两者的区别。成果可以为研究深埋隧道开挖过程中微震震源处围岩的破裂过程提供借鉴。
In order to analyze the size, mechanism and process of surrounding rock fracture during the excavation of deep tunnel, and improve the safety during the excavation of tunnel. This paper takes the tunnel in Yunnan province as the research object, builds a microseismic monitoring system in the tunnel, uses the double-difference positioning method to locate the microseismic components during the tunnel opening process, and studies the evolution law of source parameters such as energy ratio, static stress drop, dynamic stress drop, etc. The results show that: (1)The failure mode of the surrounding rock during the excavation of the tunnel is mainly tensile failure. (2)The static stress drop of the tunnel is several orders of magnitude smaller than that of natural earthquake and mine microseism, which indicates that the stress adjustment of surrounding rock of the tunnel is relatively small, and the dynamic stress drop of the tunnel is smaller than the static stress drop, which indicates that the surrounding rock of the tunnel is too fractured. (3)The size of source rupture of the tunnel is larger than that of shallow-buried tunnel, but smaller than mine micro-earthquake and natural earthquake. The above results can provide a reference for further study of the fracture process of surrounding rock at the microseismic source during the excavation of deep tunnel, and thus evaluate the risk of tunnel excavation.
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