管线渗漏水范围对浅埋隧道围岩变形和破坏的影响

 管线渗漏水是城市浅埋隧道施工安全事故的重要诱因，明确管线渗漏水对浅埋隧道围岩变形和破坏的影响规律是安全事故防控的基础。针对VI级围岩浅埋地铁隧道，采用平面应变模型试验研究管线渗漏水范围对围岩变形和破坏的影响规律。试验结果表明：(1) 管线渗漏水作用下，隧道尚未开挖就产生明显的地表沉降，随着渗漏水范围的增加，地表沉降值和沉降范围也随之增大，但当管线渗漏水范围到达拱顶后，其继续增大对地表沉降的影响程度明显减弱。(2) 管线渗漏水作用下，隧道开挖前地表即产生明显的竖向裂缝，随着地表沉降的增加，裂缝的深度和宽度均同步增加；隧道开挖后，地表竖向裂缝的深度和宽度随地表沉降的变化速率较隧道开挖前有所减小。(3) 管线渗漏水范围越大，隧道开挖后造成地层破坏的程度越剧烈；小范围管线渗漏水情况下，管线渗漏水范围对围岩破裂面形状的影响不大；中等范围和大范围管线渗漏水情况下，管线渗漏水范围的包络线和围岩破裂面高度吻合，且破裂面相对于无渗漏水影响的情况更为陡峭。

INFLUENCE OF PIPELINE LEAKAGE RANGE ON GROUND DEFORMATION AND FAILURE DURING SHALLOW TUNNELLING

Pipeline leakage is one of the important issues during shallow tunnelling in urban area. To determine the deformation patterns and the failure mechanisms of a shallow tunnel influenced by pipeline leakage is of great importance for the safety of the tunnel project. Plane strain model tests were performed to study the influence of the range of pipeline leakage on the deformation and failure of the surrounding rock of class VI during shallow tunnelling. It is found that notable ground surface settlement occurs due to the pipeline leakage before tunnel excavation. With the increase of the range of leakage，the magnitude and the range of the ground surface settlement also increases. However，when the pipeline leakage reaches the tunnel vault，the influence of the range of leakage on the ground surface settlement decreases significantly. There are several vertical cracks visible on the surface due to the pipeline leakage before tunnel excavation. With the increase of the ground surface settlement，the depth and width of the cracks increase simultaneously. However，the variation rates of the depth and width of the cracks with the ground surface settlement decreases after tunnel excavation. The larger the range of the pipeline leakage is，the more severe the failure of the surrounding rock after tunnel excavation. When the range of leakage is small，the shape of fracture plane of surrounding rock is scarcely influenced. However，when the range of leakage is large enough，the fracture plane is closely related to the boundary of the pipeline leakage and the fracture plane is steeper than that one without leakage.