充填型岩溶隧道仰坡滑塌机制及稳定性控制技术——以宜宾巡场至玉和公路下坝隧道出口段为例

Slope Landslide Mechanism and Stability Control Technology of Filled Karst Tunnels:A Case Study of Xiaba Tunnel Exit Section of Xunchang-Yuhe Highway in Yibin,China

为解决充填型岩溶隧道进洞过程中引起的仰坡滑塌问题,利用现场调查和MultiFracS多物理场断裂分析软件,对隧道进洞过程中仰坡体内裂缝发展过程和围岩变形情况进行分析,提出洞口仰坡加固措施并进行效果评价,得出如下结论:1)连续降雨是引起仰坡滑塌的直接原因,随着含水率的增加,碎石土充填物抗剪强度降低,溶腔区位移变化显著且出现微裂隙;当含水率增加至20%时,溶腔区裂缝进一步发展,局部出现开裂,地表滑动位移不断增加。2)隧道进洞施工扰动加速了地表覆盖层与下伏基岩间贯通裂缝的形成,仰坡体呈现整体滑动趋势。基于现场调查和数值分析,采用“缓坡+钢锚管/锚索框架梁”的仰坡防护形式,用注浆钢锚管替代锚杆和部分锚索,能够避免溶腔内碎石土在雨水下渗中产生变形破坏。经现场实测数据验证,加固后的仰坡在隧道二次进洞过程中处于稳定状态,隧道洞内变形和地表沉降均得到了有效控制。

During tunnel excavation in a filled karst cavity,slope landslides easily occur.Therefore,field investigation and MultiFracS fracture analysis software are used to analyze the causes of crack development in the slope and the deformation of the surrounding rock,reinforcement measures for the slope are proposed,and reinforcement effects are evaluated.The following conclusions are drawn:(1)Continuous rainfall is the direct cause of the landslide of the slope.With an increase in the water content,the shear strength of the filled gravel decreases,causing considerable displacement of the karst cavity and cracks.When the water content increases to 20%,cracks in the cavity area develop further,local cracks appear,and the surface sliding displacement continues to increase.(2)The tunnel excavation disturbance accelerates the formation of through cracks between the surface cover and underlying bedrock,and the slope exhibits an overall sliding trend.Based on the field investigation and numerical analysis,the slope protection form of the"gentle slope+steel anchor pipe/anchor cable frame beam"is adopted and the anchor rod and part of the anchor cable are replaced with the grouting steel anchor pipes,which could help prevent the deformation and damage of the gravel soil in the cavity during the infiltration by rain.The field-measured data demonstrate that the reinforced slope remains stable during the secondary tunneling process,thereby effectively controlling the deformation in the tunnel and the surface settlement.