成昆铁路保安营隧道大变形岩爆共生特征及成因分析

On the Characteristics and Genesis of the Coexistence of Large Deformation and Rockburst in Baoanying Tunnel of Chengdu-Kunming Railway

在高地应力环境下,成昆铁路保安营隧道硬质岩间夹软质岩地层中出现了大变形和岩爆共生问题,严重威胁了施工安全。本文在分析隧址区高地应力环境特征、岩性组合、岩体强度及岩体刚度特性等因素的基础上,对大变形和岩爆共生的特征及成因进行了研究,得出主要结论如下:(1)隧址区的极高地应力环境是产生大变形和岩爆的内动力地质条件;(2)薄-中厚层硬质砂岩夹页岩开挖变形主要表现为隧底隆起、拱顶下沉及类似软质岩的岩体松动、水平挤出,厚-巨厚层硬质砂岩夹页岩开挖变形主要表现为岩爆;(3)层间小间距刚度低的页岩岩体以隧底隆起变形及边墙挤压变形破坏为主,厚层状刚度高的砂岩岩体以岩爆变形为主;不同层厚组合模式的硬质砂岩和软质页岩在高地应力条件下兼具大变形和岩爆共生的变形特性。

Under the environment of high in-situ stress,the coexistence of large deformation and rockburst occurred in the weak rock stratum sandwiched between hard rocks in Baoanying Tunnel of Chengdu-Kunming Railway,which seriously threatened the construction safety.On the basis of analyzing the characteristics of high in-situ stress environment,lithologic association,rock mass strength,and rock mass stiffness in the tunnel site area,this paper studies the characteristics and causes of the coexistence of large deformation and rockburst,and draws the main conclusions as follows:(1)The extremely high in-situ stress environment in the tunnel area is the internal dynamic geological condition that produces large deformation and rockburst.(2)The excavation deformation of thin-medium-thick hard sandstone with shale is mainly characterized by tunnel floor upheaval,vault subsidence,rock mass loosening and horizontal extrusion like weak rock,while the excavation deformation of thick-huge thick hard sandstone with shale is mainly characterized by rockburst.(3)Shale rock mass with small interlayer spacing and low stiffness is mainly caused by tunnel floor upheaval deformation and sidewall extrusion deformation,while sandstone rock mass with high thick stiffness is mainly caused by rockburst deformation.Hard sandstone and soft shale with different thickness combination modes have the deformation characteristics of coexistence of large deformation and rockburst under high in-situ stress.