目的目的为分析上覆溶洞对隧道的影响,进行损伤-渗流耦合作用下上覆溶洞隧道突水灾变规律的研究。方法方法以重庆市双碑隧道工程为背景,基于三线性应变软化模型建立岩体损伤-渗流耦合模型,采用FLAC3D对隧道开挖通过上覆溶洞过程中的围岩变形、塑性区、渗透系数和涌水量进行数值模拟分析,并对比分析了不考虑岩体损伤-渗流耦合作用和不同溶洞水压对上覆溶洞隧道突水灾变特征的影响。结果结果上覆溶洞水压为1.8MPa时,隧道开挖通过上覆溶洞中心5.0m后,隧道围岩在溶洞与隧道间产生2条“八字形”的导水裂隙带,导致溶洞与隧道间岩体整体滑动约600mm,整个滑动体近似梯形,其顶、底、高分别为3.6,9.6,8.4m;隧道开挖未到达上覆溶洞时,其最大涌水量不超过0.01m3/s,而通过上覆溶洞中心0,2.5,5.0m后,其最大涌水量分别为0.022,0.185,0.743m3/s;上覆溶洞水压为1.2,1.8,2.4MPa时,隧道通过上覆溶洞后的最大涌水量分别为0.031,0.0743,1.365m3/s。结论结论隧道开挖通过上覆溶洞过程中,上覆溶洞水压超过临界值时,隧道会发生冒顶坍塌和突水事故,且突水表现出一定的滞后性和大体量性;溶洞水压越大,隧道会越早突水,最终突水量越高;为模拟再现岩溶隧道开挖过程中的突水灾变时空演化过程,必须考虑岩体的损伤-渗流耦合作用。本文研究成果可为岩溶隧道工程围岩稳定控制提供重要依据。

Objectives  To analyze the impact of overlying karst caves on tunnels, this study investigates the law of water inrush disasters in overlying karst tunnels under damage-seepage coupling. Methods Based on the Shuangbei Tunnel project in Chongqing, a rock mass damage-seepage coupling model is developed us⁃ing the trilinear strain softening model. FLAC3D is employed to simulate the deformation, plastic zones, permeability coefficients, and water inflow of the surrounding rock during tunnel excavation through the overlying karst cave. The influence of rock mass damage-seepage coupling and varying karst cave water pressures on the water inrush disaster characteristics of the overlying karst tunnel is compared and ana⁃lyzed. Results When the water pressure in the overlying karst cave is 1.8 MPa, after the tunnel excavation passes through the center of the overlying karst cave by 5.0 m, two “eight-shaped” water-conducting frac⁃ture zones form between the karst cave and the tunnel, causing the rock mass to slide by about 600 mm. The sliding body takes on an approximately trapezoidal shape, with top, bottom, and height dimensions of 3.6 m, 9.6 m, and 8.4 m, respectively. When the tunnel excavation does not pass through the overlying karst cave, the maximum water inflow does not exceed 0.01 m/s. However, after passing 0 m, 2.5 m, and 5.0 m beyond the center of the overlying karst cave, the maximum water inflow reaches 0.022 m/s, 0.185 m/s, and 0.743 m/s, respectively. For water pressures of 1.2 MPa, 1.8 MPa, and 2.4 MPa in the overly⁃ing karst cave, the maximum water inflows after passing through the cave are 0.031 m/s, 0.0743 m/s, 1.365 m/s, respectively. Conclusions During tunnel excavation through the overlying karst cave, if the wa⁃ter pressure in the cave exceeds the critical threshold, the tunnel will experience a roof collapse and water inrush accidents. The water inrush exhibits a certain delay and a large volume characteristic. The higher the water pressure of the karst cave, the earlier the water inrush occurs, and the greater the final water in⁃flow. To accurately simulate the spatial and temporal evolution of water inrush disasters during karst tunnel excavation,  the damage-seepage coupling effect in rock mass must be considered. The findings of this study provide an important insights for the stability control of surrounding rock in karst tunnel engineering.