盾构近接施工对桥桩沉降影响分析及保护措施

Influence of Shield Close-spaced Construction on Settlement of Bridge Pile and Protective Measures

以地铁盾构隧道近接侧穿既有桥桩工程为背景,基于现场实测数据,对盾构近接侧穿施工全过程中桥桩沉降的变化规律、各阶段的沉降占比、隧道洞身软弱地层分布和袖阀管打设方式对桥桩沉降的影响进行分析。分析结果表明:软弱地层中盾构近接侧穿桥桩时,桥桩竖向位移整体呈“先小幅上升,后下沉”的变化规律;桥桩沉降主要发生在盾构通过期间及通过后一周,约占总沉降的80%~90%;当隧道与桥桩平面净距小于2D时,对临近隧道的桥桩采取桩周全包袖阀管预注浆加固措施,可有效降低盾构施工对桥桩沉降的影响;隧道洞身范围软弱土层分布比例越高,桥桩沉降越大;桩周袖阀管注浆孔应优先考虑垂直打设,避免注浆盲区,以保证土体加固及桥桩沉降控制效果。

During close-spaced tunnel construction passing through existing bridge piles,and based on the field measured data,the change rules of bridge pile settlement,the settlement proportion of each stage,the distribution of soft strata in the tunnel body,and the impact of sleeve valve pipe driving method on the bridge pile settlement were analyzed.The conclusion shows that when shield tunneling side through bridge piles in soft strata,the vertical displacement of the bridge pile shows the change rule of“first rising slightly,then sinking”;the settlement of bridge piles mainly occurs during and one week after the shield passes,accounting for 80%~90%of the total settlement;when the plane clear distance between the tunnel and the bridge pile is less than 2D,the bridge pile adjacent to the tunnel shall be pre-grouted with sleeve valve pipe around the pile for reinforcement,which can effectively reduce the impact of shield construction on the settlement of the bridge pile;the higher the distribution proportion of soft soil layer in the tunnel body,the greater the settlement of bridge piles;the sleeve valve pipe grouting hole around the pile shall be set vertically to avoid the blind area of grouting,so as to ensure the effect of soil reinforcement and bridge pile settlement control.