水平层状围岩隧道初期支护参数研究

Study on Primary Support Parameters of Tunnel in Horizontal Layered Surrounding Rock

针对水平岩层的工程地质特性,依托吕梁—临县铁路车赶隧道工程实例,依据室内室外试验、现场监测结果综合分析在该类岩层中隧道开挖支护的锚杆轴力、围岩压力、钢架应力及喷射混凝土应力的变化规律,探讨初期支护参数的合理性。结果表明:拱部锚杆受力较大,边墙锚杆受力很小,可取消边墙锚杆,适当增加拱部锚杆长度;开挖后围岩压力释放较快,建议在不良地质段或有水地段增设超前支护;全环安设格栅拱架偏于安全,可优化为仅对拱部增加格栅拱架,形成"格栅拱架拱部带帽+锚网喷"支护;水平岩层施工控制的关键点在拱部,当围岩较差或遇水时,可优先考虑对拱部围岩采用超前小导管注浆加固。采用优化后的初期支护参数安全顺利地通过了水平岩层地段,说明支护参数取值合理。

Based on engineering geological characteristics of horizontal layered surrounding rock,the C hegan Tunnel in Lyuliang-Linxian railway was studied and its initial support rationality w as discussed. According to the indoor and outdoor test and field monitoring results,comprehensive analysis of anchor bolt axial force,rock mass pressure,steel stress,concrete stress and deformation of primary support in the rock tunnel excavation was conducted. The results shows that arch anchor stress is large,requiring longer length,while side wall anchor force is small and ignorable. After excavation rock pressure is released quickly. It is suggested to use support in advance in undesirable geological section or in area full of water. A full grid arch is too conservative,and partial installation at the arch,i. e. ,grid arch with cap plus anchor net spray support is advisable. The key to construction control of horizontal layered rock is the arch. When the surrounding rock is undesirable or full of water,advanced small pipe grouting may be used for arch surrounding rock. The initial support parameters using this optimized technology were proved rational by the practice.