圆宝山隧道炭质板岩大变形段初期支护结构受力特性研究

为了准确掌握丽香铁路圆宝山隧道炭质板岩大变形段初期支护结构受力特性,结合深埋炭质板岩隧道大变形特点,通过调查分析发现炭质板岩具有显著的各向异性特征,在地下水、高地应力及施工扰动等复杂因素作用下表现出显著的蠕变特性,从而导致隧道发生大变形。同时,对圆宝山隧道展开围岩变形及初期支护受力监测,监测结果表明,薄层炭质板岩段围岩的变形速率、变形量整体上较中厚层炭质板岩段围岩大,且达到稳定所需的时间更长;围岩压力与钢拱架应力基本呈从拱顶到拱脚减小的趋势,且围岩压力最大值出现在拱肩,而钢拱架应力最大值分布位置不固定,常见分布位置为两侧拱墙上下,这与钢拱架因发生扭曲而设置横支撑基本吻合;变更支护参数后,围岩的时效特性有明显改善,尤以薄层炭质板岩段围岩最为明显,同时围岩压力分布更加均匀,钢拱架出现拉应力现象不再集中。基于上述研究成果,选择I18型工字钢焊制钢架、设置间距为0.6m、喷射厚为27cm的C25混凝土作为初期支护,同时采用"弱爆破、短进尺"的掘进方式,以达到控制深埋炭质板岩隧道围岩变形的目的。

Study on mechanical characteristics of initial supporting structure of large deformation section of carbonaceous slate in Yuanbaoshan tunnel

In order to accurately grasp the mechanical characteristics of the initial supporting structure of the large deformation section of carbonaceous slate in Yuanbaoshan tunnel of railway,and combining with the large deformation characteristics of the deep-buried carbonaceous slate tunnel,the investigation and analysis show that the carbonaceous slate has obvious anisotropic characteristics.Under the complex factors of groundwater,high ground stress and construction disturbance,the creep behavior of the tunnel is obvious,which leads to large deformation of the tunnel.At the same time,the surrounding rock deformation and the initial supporting forcemonitoring of the circular Yuanbaoshan tunnel are monitored.The monitoring results show the deformation rate and deformation of the surrounding rock in the thin carbonaceous slate area are larger than those in the middle thick carbonaceous slate area,and the time needed for stabilization is longer.The surrounding rock pressure and stress of steel arch is from the arch to arch foot decreases,and the maximum value appeared in the surrounding rock pressure of spandrel,but the maximum stress of steel arch segment is not fixed,widely distributed in both sides of the wall under the arch,which is basically consistent with steel arch become distortion and set up horizontal support horizontal support.When the supporting parameters are changed,the aging characteristics of the surrounding rock are obviously improved,especially in the area of rock thin carbonaceous slate is most obvious,at the same time,the rock pressure distribution is more uniform and the steel arch tensile stress is no longer concentrated.Based on the above research results,I18 welded steel frame with 0.6 m spacing and 27 cm thick C25 concrete is selected as initial support.Meanwhile,weak blasting and short footage are adopted to control the surrounding rock deformation of deep-buried carbonaceous slate tunnel.