深埋岩溶隧道爆破开挖对围岩损伤及渗流特性的影响

Influence of Blasting Excavation of Deep Karst Tunnel on Damage and Seepage Characteristics of Surrounding Rock Mass

深埋岩溶隧道开挖会造成围岩特殊的损伤破坏形式,并且损伤区也会影响围岩渗流场及隧道边界的涌水状况,对深埋岩溶隧道爆破开挖作用下围岩的损伤及渗流特性有重要的研究意义。为了研究爆破开挖对深埋岩溶隧道围岩损伤及渗流的影响规律,基于COMSOL Multiphysics软件建立数值模型并嵌入应力-渗流-损伤耦合方程式进行计算,采用解析法计算了简化条件下岩溶隧道开挖时围岩的应力分布,并与数值计算结果进行比较。结果表明:解析法与数值法计算的围岩应力分布有一致性,爆炸荷载使靠近溶洞侧隧道肩部及脚部区域会产生较大的拉应力;爆破后会在隔水岩柱形成“齿”状损伤区,同时引起肩部及脚部区域流速的增加,其可作为判断溶洞方位的参考依据;溶洞净距减小、洞径及水压增加会引起“齿”延伸倾角及最大涌水位置变化、隧道边界涌水量的增加,可根据“齿”延伸方向判断损伤区检测的合理方位,根据最大涌水位置变化、隧道边界涌水量的变化,合理调整涌水防治措施强度及重点防治部位。研究成果可为溶洞位置判定、隧道损伤区检测以及边界涌水防治措施提供参考。

The excavation of deep buried karst tunnel will cause special damage and failure forms of the surrounding rock mass,and the damage zone will also affect the seepage field of the surrounding rock mass and the water inflow condition of the tunnel boundary.To understand the impact of blasting excavation on surrounding rock damage and seepage,a numerical model was created using COMSOL Multiphysics software.The model included a stress-seepage-damage coupling equation for calculations.The stress distribution of surrounding rock during tunnel excavation was calculated using both analytical and numerical methods.The results showed that there was consistency between the two methods.Large tensile stress was observed near the shoulder and foot of the tunnel due to the blasting load.Additionally,a tooth-shaped damage zone was formed in the water-resisting rock mass after blasting,leading to increased infiltration velocity in the shoulder and foot area,which can aid in determining the direction of the cave.Furthermore,changes in cave spacing and diameter,as well as water pressure,can influence the“tooth”extension angle,maximum water inflow position,and water inflow at the tunnel boundary.By considering the extension direction of the“teeth”,a reasonable position for detecting the damage zone can be determined.Moreover,adjustments in water inflow prevention measures and key prevention and control areas can be made based on changes in the maximum water inflow position and water inflow on the tunnel boundary.