西(宁)成(都)铁路高地应力节理发育软岩地层隧道支护体系研究

Study on Tunnel Support System in Soft Rock With Developed Joints and High Ground Stress in Xi'ning-Chengdu Railway

为保证西成铁路高地应力节理发育软岩大变形隧道安全修建,采用现场勘察、室内试验、地应力测试、工程类比、数值模拟等方法展开研究,结果表明,西成铁路与毗邻兰渝线地质条件类似,均以二叠系、三叠系板岩与砂岩为主,层理清晰、节理裂隙发育,地应力以水平主应力为主导,水平主应力在10~30 MPa之间,竖直主应力在4~13 MPa之间,有较强水平构造应力作用,兰渝线控制围岩变形主要采用增加预留变形量、自进式长锚杆、钢花管加固、增加初支及衬砌刚度、钢纤维喷射混凝土等技术措施。在此基础上针对西成铁路节理发育软岩大变形主要发生在垂直节理倾角方向上的特点,提出首先增大矢跨比,然后增大钢拱架刚度,对于Ⅲ级大变形在垂直节理方向设置预应力锚索的非对称大变形隧道支护体系,该支护体系相比传统支护体系能够减小13.8%~21.2%软岩变形,对于控制节理发育软岩变形效果良好。

To ensure safe construction of large deformation tunnels in soft rock with developed joints and high ground stress in Xining-Chengdu Railway,this paper adopts field investigation,indoor test,geostress test,engineering analogy,numerical simulation for study.It is found that geological conditions are similar to those of adjacent Lanzhou-Chongqing Railway,which are dominated by the Permian and Triassic slate and sandstone,with clear bedding,developed joints and fissures,and geostress is dominated by the horizontal principal stress,the horizontal principal stress is between 10 and 30 MPa,and the vertical principal stress is between 4 and 13 MPa,with strong horizontal tectonic stress and horizontal tectonic stress.The Lanzhou Chongqing Railway mainly adopts some technical measures to control deformation of soft rock,such as increasing reserved deformation,self advancing long anchor bolt,steel pipe reinforcement,increasing initial support and lining stiffness,steel fiber shotcrete,etc.On this basis,in view of characteristics that large deformation of soft rock with developed joints in Xining-Chengdu Railway mainly occurr in the direction of vertical joint dip.And it is proposed to increase rise-span ratio first,increase rigidity of steel arch,and set prestressed anchor cables in vertical joint direction for class III large deformation.The support system reduces deformation of rock mass by 13.8%~21.2%compared with the traditional support system,which is good for controlling large deformation of jointed soft rock.