盾构切桩下穿复合地基对砌体房屋基础沉降影响数值模拟研究

Numerical modeling study on the deformation influence of cutting pile in the shield tunneling through composite ground under the existing masonry structure

盾构下穿切除复合地基部分桩体,导致复合地基中桩与土的荷载分担和传递规律发生变化,降低了复合地基承载力,诱发砌体房屋基础沉降和结构变形。依托郑州地铁5号线某盾构隧道工程现场监测案例,建立盾构切桩全过程三维数值分析模型,对盾构切桩下穿全过程中地层沉降特征进行了分析。研究结果表明:在盾构切桩下穿区段的地层沉降槽宽度要略大于非切桩和无桩区段;砌体房屋累计最大沉降位置和差异沉降最大位置均集中在盾构切桩下穿区段内盾构隧道轴线附近;随着盾构机开挖面位置的不断变化,砌体房屋的变形和受力状态以及最大应力点位置也随之改变;对房屋最大沉降量的影响因素比重排序为:切桩长度>桩身刚度>房屋结构刚度。研究成果对城市地铁隧道施工过程中受盾构切桩影响的砌体房屋保护有重要的参考价值。

Cutting some piles of the composite ground during shield tunneling will change the load sharing between pile and soil,and also change the transferring law,so the bearing capacity of the composite ground may be reduce and the masonry building foundation settlement and structure deformation maybe occur.A case study of a shield tunneling project of Zhengzhou Metro Line No.5 was carried out.A three-dimensional numerical simulation model is established to analyze the characteristics of building settlement during the whole process tunneling.The study shows that the width of the ground settlement groove in the section underneath the pile cutting area is slightly larger than that in the non-cutting and the non-pile section;the cumulative maximum settlement position and the maximum differential settlement position of the masonry building are concentrated near the axis of the tunnel in the pile cutting section;with the shield tunneling face changes,the deformation and stress state of the masonry building and the position of the maximum stress point should also change accordingly;the impact factors on the maximum settlement of the building are listed in the descending sequence as pile cutting length,pile body stiffness and building structure stiffness.The study results have great reference value for the protection of masonry buildings affected by cutting pile during the construction of urban subway tunnels.