基于位移反演的中老铁路泥砂岩互层隧道支护时机研究

Support Timing of Mudstone-Sandstone Interbedded Tunnel in China-Laos Railway Based on Displacement Inversion

为探究大断面泥砂岩互层隧道合理的支护时机,依托中老铁路会排山隧道,开展大断面泥砂岩互层隧道支护时机以及全位移反演研究。首先,通过三轴压缩试验对现场岩块的工程特性进行研究,并采用Hoek-Brown强度准则进行修正得到岩体力学参数;然后,对全位移进行推导求解,结合现场监测数据得到全位移与实测位移的关系式;最后,通过数值模拟得到拱顶沉降与塑性区半径的关系,找出特征点确定初期支护以及加强支护的时机,并根据实测位移与全位移的关系式得到基于现场监测数据的最佳支护时机。研究结果表明:1)泥砂岩互层围岩条件差,力学指标参数较单一围岩降低了1/2左右;2)实测位移为全位移的60%~70%,得到了实测位移与全位移的关系式;3)隧道需要随挖随支,当现场监测拱顶沉降达到170 mm且无收敛趋势时或现场监测变形速率异常时,应采取加强支护措施。

The mudstone-sandstone interbedded tunnel is prone to large deformation,thus the reasonable support timing is extremely important.Study is conducted on the support timing and total displacement inversion of the Huipaishan tunnel of China-Laos railway in mudstone-sandstone interbedded strata.First,the engineering characteristics of the rock mass are studied using triaxial compression test,and the mechanical parameters of the rock mass are modified based on the Hoek-Brown strength criterion to provide the basis for the later numerical calculation.Then,through derivation of the total displacement,the relationship between the total displacement and the measured displacement is obtained based on field monitoring data.Finally,the relationship between the crown settlement and the radius of the plastic zone is obtained using numerical simulation,and the characteristic points are found to determine the timing of the primary support and the strengthening support.According to the relationship between the measured displacement and the total displacement,the optimum support timing based on the field monitoring data is obtained.The results show the following:(1)The condition of mudstone-sandstone interbedded surrounding rock is poor,and the mechanical index parameters are about half lower than that of single-component surrounding rock.(2)The measured displacement accounts for 60%-70%of the total displacement,and the relationship between the measured displacement and the total displacement is obtained.(3)The tunnel needs to be supported with the excavation,and when the on-site monitoring crown settlement reaches 170 mm and there is no convergence trend,the support measures should be strengthened.