护拱回填暗挖法隧道支护结构安全性评价

文章依托九景衢铁路荆生坞隧道工程,介绍了护拱回填暗挖法的施工步序,利用弹性理论推导了护拱与初期支护拱部的围岩荷载分担比例计算公式,采用极限平衡理论建立了边墙处围岩受力模型,推导了初期支护边墙附加围岩压力计算公式,最后通过建立荷载-结构模型,计算了护拱和初期支护的内力、安全系数,评价了护拱和初期支护安全性。结果表明:初期支护围岩荷载分担比例与护拱和初期支护的弹性模量、厚度有关,荆生坞隧道初期支护围岩荷载分担系数约为30%;护拱拱脚竖向压力导致边墙上部围岩沿破裂面滑动,对初期支护边墙上部产生一个水平向的附加围岩压力;九景衢铁路荆生坞隧道护拱回填暗挖段护拱和初期支护均处于安全状态,初期支护安全性随围岩荷载分担系数的增大而略有降低。

Safety Evaluation of Support Structure of the Tunnel Excavated by Mining Method with Arching and Backfilling

Based on the Jingshengwu tunnel of the Quzhou-Jiujiang railway,the construction steps of mining meth od with arching and backfilling are introduced,an calculation formula for the rock load sharing proportion of the arching structure and primary support arch structure is deduced by elastic theory,a mechanical model of surround ing rocks at sidewall is established by ultimate equilibrium theory,and a formula for calculating additional surround ing rock pressure on the sidewall of primary support is derived,the internal force and safety factors of arching struc ture and primary support structure are calculated by establishing a load-structure model,and the safety of arching structure and primary support structure is evaluated.The results show that:rock load sharing proportion of primary support is related to elastic modulus and thickness of arching structure and primary support structure,the rock load sharing coefficient of primary support of Jingshengwu tunnel is about 30%;the vertical pressure at arch spring of arching structure causes the rocks above sidewall slide along the fracture surface and horizontal additional sur rounding rock pressure is produced at the upper sidewall of primary support;the arching structure and primary sup port structure of Jingshengwu tunnel are in safe state,the safety of primary support slightly decreases with the in crease of rock load sharing factor.