不同位置充水溶洞对隧道开挖临界拱圈影响的数值分析

为揭示不同空间位置溶洞对隧道开挖拱圈的受力情况及危险程度,采用数值模拟方法,建立了分布于隧道拱顶、拱腰、边墙、拱脚及拱底的5种充水溶洞模型,在渗流模式下进行耦合收敛计算。在每一种工况下,采用全断面法模拟隧道开挖,随着开挖步的推进,溶洞与隧道间围岩逐渐达到塑性区贯通,以此时的隧道开挖拱圈为临界拱圈,并在临界拱圈均匀设置孔隙水压力监测点,分别提取各监测点在模型渗流平衡状态与开挖至临界拱圈时的孔隙水压力,计算两者孔隙水压力相对变化率。根据风险等级,将孔隙水压力相对变化率划分为红、橙、黄三级范围,最终基于数值计算结果可确定各工况的临界拱圈危险分区。该研究成果可用以指导隧道在不同空间溶洞下的合理施工和安全措施布控。

Research on the Influence of Water-filled Karst Cave in Different Position around Tunnel to the Critical Arch Ring during Construction

In order to reveal the stress condition and danger degree of karst cave in different space to tunnel excavation arch ring,numerical simulation method is used to establish five kinds of water-filled karst cave models,with the karst cave distributed in the tunnel vault,hance,sidewall,arch foot and arch bottom.Coupling-convergence calculation is carried out under the seepage flow mode.In each working condition,the full-section method is adopted to simulate tunnel excavation.With the advancing of excavation step,the surrounding rocks between the karst cave and the tunnel gradually reach the plastic zone connection,and the tunnel excavation arch ring at this time is taken as the critical arch ring.The monitoring points of pore water pressure are uniformly set up in the critical arch ring,the pore water pressure of each monitoring point is extracted respectively in the model seepage equilibrium state and excavation to the critical arch ring,and the relative change rates of pore water pressure are calculated.According to risk levels,the relative change rate of pore water pressure is divided into three levels of red,orange,and yellow.Finally based on the results of numerical calculation,the risk zoning of critical arch ring can be confirmed in different working conditions.The research results can be used to guide the reasonable construction and safety control of tunnel with different space karst caves.