成兰铁路千枚岩隧道初期支护形式试验研究

Experimental study on primary lining form of tunnels in phyllite on Chengdu-Lanzhou railway

在高地应力软岩地层中开挖隧道,易发生大变形,合理地选用初期支护的钢架形式,对软岩大变形的控制是非常重要的。本文依托成兰铁路-茂县隧道,通过现场试验和数值计算研究挤压性软岩大变形隧道的初支钢架选型,主要得出以下结论:(1)高地应力软岩隧道不宜选用强度较弱的钢架作为第一层支护,第一层支护应能保证支护封闭时的合理洞形;(2)挤压性大变形隧道宜采用多层、多次的支护方法,适当释放围岩应力,保证隧道的长期稳定;(3)大变形隧道多采用分部工法开挖,易导致支护结构受力不均,应提早支护封闭时机,改善结构受力。

The large deformation of surrounding rocks is easily caused by excavating tunnels in squeezing soft rocks. It is very important to control the large deformation of soft rock by selecting the reasonable steel frame of the initial support. In this paper,based on the Maoxian tunnel of Chengdu-Lanzhou railway,through the field test and numerical calculation,the selection of the primary support steel frame of the tunnel with large deformation of the squeezing soft rock is studied.The main conclusions are as follows:( 1) The steel frame with low strength should not be used as the first layer support of tunnel in squeezing soft rock,and the first layer support should be able to ensure the reasonable shape of the tunnel.( 2) The tunnel with large squeezing deformation should be supported by multiple layers and multiple supports,and the stress of surrounding rock should be released to ensure the long-term stability of the tunnel.( 3) The excavation of the tunnel with large deformation is mainly caused by partial excavation method,which can easily lead to the uneven stress of the supporting structure,and the support should be closed rapidly in advance to improve the structural stress.