新近系泥岩隧道初期支护受力特性研究

富水区泥岩隧道开挖后经常出现支护结构大变形乃至开裂现象,影响隧道的施工和长期运营安全。为掌握新近系泥岩隧道支护结构和围岩的变形动态,开展相应的室内试验与现场监控量测以及数值模拟。采用室内试验方法获得泥岩的物理力学参数;通过现场监测方法得到围岩压力、钢拱架应变;采用数值模拟的方法获得泥岩软化前、后拱顶及拱脚沉降量、围岩压力、径向位移值的大小。研究结果表明:泥岩呈弱崩解性,且具有一定膨胀性,是导致围岩变形持续时间较长的主要原因;多数测点钢拱架弯曲,导致初期支护承载力不足,进而引起初衬混凝土掉块脱落;泥岩软化后,隧道同一位置处拱顶、拱脚沉降量、围岩压力、径向位移值均远大于泥岩软化前的数值,泥岩遇水软化是导致隧道支护结构产生大变形的原因之一。研究方法和结论对新近系泥岩隧道的设计和施工有一定的参考价值。

Analysis of Mechanical Characteristics of Tunnel Primary Lining in Neogene System Mudstone

Large deformation and cracking of lining often appear in mudstone tunnels in water-rich area and the safety of the tunnels during construction and long-term operation are likely to be affected. In order to master the cracking mechanism of tunnel lining structure and deformation dynamics of surrounding rock in Neogene System mudstone,laboratory test,in-situ monitor and numerical simulation are carried out.Physical and mechanical parameters of mudstone are obtained from laboratory test and the pressure between surrounding rock and preliminary support,and the strain of steel arch are gained from in-situ monitoring. The settlement value of vault and arch foot,surrounding rock pressure and axial force of steel arch before and after mudstone is softened are acquired by way of numerical simulation. The research results show that mudstone is weakly disintegrated and expansive,which contributes to the long-time rock deformation. The bending of steel arch at most measurement points results in insufficient initial support bearing capacity and dropping of primary lining concrete. The settlement of vault crown and arch foot,the stress of initial support and the radial displacement measured at the same point after the mudstone is softened are much larger than those before it is softened. The softening of mudstone is one of the causes of large deformation of tunnel support structure. The analytical method and results may provide some references for the design and construction of tunnels in Neogene System mudstone.