绿泥石片岩隧洞大变形特征及控制措施——以滇中引水工程香炉山隧洞为例

为进一步掌握深埋软岩隧洞开挖过程中大变形规律,依托在建滇中引水工程香炉山隧洞绿泥石片岩段,运用有限差分软件FLAC^3D,对比分析软岩隧洞更为适用的本构模型;并采用预留核心土台阶开挖法(工况1)、单侧壁导坑法(工况2)和中隔壁开挖法(工况3)对大变形的控制效果进行对比分析。结果表明:采用Hoek-Brown(H-B)应变软化模型得到拱顶最大沉降大于理想弹塑性模型的计算结果,与实际沉降误差为9.3%;工况1及工况3对拱顶沉降的控制相较于工况2减少了20%左右,工况3对拱腰及拱墙的收敛变形相较于工况1和工况2得到明显控制。从大变形控制效果和塑性区分布来看,采用中隔壁开挖法可有效减小隧洞绿泥石片岩段的变形。

Large Deformation Characteristics and Control Measures of Chlorite Schist Tunnels: A Case Study on Xianglushan Tunnel of Water Diversion in Central Yunnan

The aim of this research is to further understand the law of large deformation during the excavation of deep-buried soft rock tunnels. The chlorite schist section of Xianglushan Tunnel under construction of the Central Yunnan Water Diversion Project is taken as a research background. Constitutive models more suitable for soft rock tunnels are compared and analyzed by using FLAC^3D. The effects of controlling large deformation by the excavation method with reserved core soil step (working condition 1), the pilot pit method on one sidewall (working condition 2) and the excavation method with middle partition wall (working condition 3) are compared and analyzed. Results unveil that the maximum settlement of the vault obtained by Hoek-Brown (H-B) strain softening model is greater than that of the ideal elastic-plastic model, and the error with actual settlement is 9.3%. The vault settlement in working conditions 1 and 3 reduced by about 20% compared with that in working condition 2, and the convergence deformation of arch waist and arch wall in working condition 3 is obviously controlled compared with working conditions 1 and 2. From the perspectives of large deformation control effect and plastic zone distribution, the excavation method with middle partition wall (working condition 3) could effectively reduce the deformation of chlorite schist segment of the tunnel.