炭质板岩隧道隧底结构裂损机理研究

Mechanism of Cracking Damage in the Bottom Structure of Carbonaceous Slate Tunnel

炭质板岩遇水软化、泥化,稳定性差,是典型的软岩地层。施工期内炭质板岩隧道易发生变形,进而出现病害问题,严重影响隧道施工进度与安全。以西南地区某在建隧道为依托工程,针对隧底结构病害段所处的炭质板岩地层,通过室内材料物相组成分析试验,明确该段地层炭质板岩以石英、绿泥石等具有遇水易软化及膨胀特性的矿物为主要组成成分,得出炭质板岩大变形产生的原因。建立基于扩展Drucker-Prager准则的有限元精细化网格分析模型,获得不同剪胀角条件下隧道结构底部的裂损形态及周边围岩塑性区分布。数值仿真结果和现场实际裂损情况对比表明,有限元结果与实际隧底结构病害特征吻合良好。

Carbonaceous slate softens and muds when exposed to water,with poor stability,making it a typical soft rock formation.During the construction period,carbonaceous slate tunnels are prone to deformation,leading to disease problems and seriously affecting the progress and safety of tunnel construction.Based on a tunnel under construction in the southwest region,this paper conducted indoor material phase composition analysis experiments on the carbonaceous shale formation in the section with structural defects at the bottom of the tunnel.It was determined that the carbonaceous shale in this section is mainly composed of minerals such as quartz and chlorite,which have the characteristics of softening and swelling when exposed to water.The reasons for the large deformation of the carbonaceous shale were identified.Establish a refined finite element mesh analysis model based on the extended Drucker-Prager criterion,and obtain the crack morphology at the bottom of the tunnel structure and the distribution of the plastic zone of the surrounding rock under different shear dilation angles.The comparison between the numerical simulation results and the actual on-site crack damage situation shows that the finite element results are in good agreement with the actual tunnel bottom structure disease characteristics.