黄土地区浅埋暗挖地铁隧道围岩压力特征研究

为了解黄土地区浅埋暗挖地铁隧道围岩压力特征,得出荷载在衬砌结构各部分中的分担比例,本文以西安地铁二号线为研究对象,选取2组不同围岩条件的测试断面,开展现场测试工作。对围岩与初期支护接触压力、初期支护与二次衬砌接触压力及二次衬砌结构应力进行研究。结果表明:隧道墙脚位置初期支护与围岩之间接触压力较大,表明这二者承受大部分垂直压力;初期支护所受围岩压力随着土体强度降低而增大,且分布形式更趋于静水压力作用特点;二次衬砌作为主要支护结构承担大部分荷载,初期支护与二次衬砌接触压力随围岩土体强度降低而显著增大,二次衬砌在支护体系中作用也随土体强度降低而凸显;二次衬砌混凝土基本受压,拱腰及以上位置应力较大,仰拱处应力较小。

Study on Characteristics of Surrounding Rock Pressure of Undercut Metro Tunnel with Shallow Buried Excavation in Loess Region

The large scale field tests of two groups of sections of different surrounding rock conditions were conducted on the construction sites of Line 2 of the Xi’an Metro so as to precisely understand the characteristics of surrounding rock pressures and obtain the loading proportion shared by all parts of the lining structure of metro tunnels with shallow buried excavation in loess regions.The contacting pressure on surrounding rock and the initial supporting system,the contacting pressure on the initial supporting system and secondary lining structure and the stress of the secondary lining structure were monitored.The research results indicate as follows: The contacting pressure on surrounding rock and the initial supporting system is comparatively large at the wall foot because both bear most of the vertical pressure;the pressure on initial supporting increases with decreasing of the soil-body strength,and it is distributed in the mode tending to be like action of the hydraulic pressure;as the main supporting system,the secondary lining structure bear most loads,and the contacting pressure on the initial supporting system and secondary lining structure increases significantly with decreasing of the soil-body strength while the role of the secondary lining structure in the supporting system becomes obvious accordingly;the stress of the secondary lining structure is basically the pressure stress,which is large at & above the position of the arch loin and is small at the position of arch invert.