盾构掘进速度对既有桩体切削变形规律的研究

Research on the influence of shield tunneling speed on the deformation of shield cutting pile foundation

盾构隧道施工在其推进过程中不可避免地要穿越地下桩,这是当前盾构隧道施工中的难点问题之一。为保证在隧道工程中盾构机切削地下桩基的施工安全和掘进效率,探究不同掘进参数下桩体的变形规律,采用PFC3D颗粒流软件,模拟在不同掘进速度下盾构切削桩基的施工过程,分析和研究在不同掘进参数下桩体沿盾构掘进方向、垂直盾构掘进方向的桩体变形和桩顶竖向沉降的变化规律。并依托江苏省苏州市桐泾路北延隧道工程进行实证分析。研究结果表明:桩体的变形主要发生在桩体与盾构机上部相交的交点至该点往上的11倍桩径范围内。当盾构机推进速度不超过15 mm/min,刀盘转速不超过2.0 r/min时,桩体沿垂直盾构掘进方向的变形大于沿盾构掘进方向的变形;反之,当盾构机推进速度超过15 mm/min,刀盘转速超过2.0 r/min时,桩体沿垂直盾构掘进方向的变形小于沿盾构掘进方向的变形。因此,当盾构机分别切削桩长为20、40 m的桩底,或者切削桩长为40 m的桩身时,其推进速度不应超过10 mm/min,刀盘转速应不应超过1.0 r/min;当盾构机切削桩长为20 m桩身时,应控制其推进速度为1~5 mm/min,刀盘转速为0.5~1.0 r/min。

During the construction of shield tunnels,it is inevitable to cross underground piles,which is one of the difficulties in current shield tunnel construction.In order to ensure the safety and excavation efficiency of shield tunnel construction when cutting through underground piles,this study explores the deformation characteristics of shield cutting piles under different excavation parameters.PFC3D software is used to simulate the construction process of shield cutting piles at different excavation speeds,and the deformation characteristics of the piles along the shield excavation direction,the vertical shield excavation direction,and the vertical settlement of the pile top are analyzed and studied under different excavation parameters.Taking the Tongjing Road North Extension Tunnel Project in Suzhou City,Jiangsu Province as an example,an analysis and study are conducted.The research results show that the deformation of the piles mainly occurs within 11 times the diameter of the shield cutting pile.When the advancement speed does not exceed 15 mm/min and the cutterhead rotation speed does not exceed 2.0 r/min,the deformation along the vertical excavation direction is greater than the deformation along the excavation direction.Conversely,the deformation along the vertical excavation direction is smaller than the deformation along the excavation direction.Therefore,when the shield cutting pile has a length of 20 or 40 meters at the pile bottom,or a cutting pile length of 40 meters at the pile body,the advancement speed should not exceed 10 mm/min,and the cutterhead rotation speed should not exceed 1.0 r/min.When the shield cutting pile has a length of 20 meters at the pile body,the advancement speed should be controlled within the range of 1-5 mm/min,and the cutterhead rotation speed should be controlled within the range of 0.5-1.0 r/min.