可拆解盾构下穿既有桥桩磨桩施工影响研究——以宁波轨道交通4号线柳宁盾构区间为例

Research on Construction Influence of Dismountable Shield Crossing underneath Existing Bridge Piles:a Case Study on Liuxi Station-Ningbo Railway Station Section on Ningbo Metro Line No.4

为解决宁波火车站过站空间有限,以及盾构过站面临吊装孔无预留、车站净空不足的难题,宁波轨道交通4号线在柳宁区间采用拼装式可拆解盾构进行掘进。在此背景下,以宁波轨道交通4号线拼装式盾构磨桩通过苍松路下立交为研究对象,阐述该区间创造性使用拼装式可拆解盾构的必要性以及刀盘分块设计的有效性,利用数值模拟对可拆解盾构刀盘强度进行研究,并利用地表沉降监测结果分析拼装式可拆解盾构磨桩施工的稳定性。结果表明:将刀盘分为一大两小3块的拆解方案,在盾构磨桩施工中的结构强度满足要求。配合盾构推进过程中的施工控制,对桥面及地表进行沉降监测。监测结果表明:地表最终累加沉降值分布于-5~2 mm,未达到预警值,说明施工过程中沉降值处于可控范围内。

There are many problems of shield tunneling through railway station,i.e.limited space,no reserved hoisting holes on shield and insufficient clearance of station.As a result,a dismountable shield is adopted to cross underneath Cangsong Road Overpass of Liuxi Station-Ningbo Railway Station Section on Ningbo Metro Line No.4.Firstly,the necessity of creative application of dismountable shield and the effectiveness of partitioning design of shield cutterhead are presented.And then the strength of shield cutterhead is studied by numerical simulation,and the stability of construction for pile cutting of dismountable shield is analyzed based on monitoring results of surface settlement.The results show that the disassembling scheme of 3 pieces(1 big and 2 small)of cutterhead can meet the requirements of the structural strength in the construction of pile cutting by shield.Finally,the settlement monitoring on the overpass deck pavement and ground surface is carried out with shield tunneling control.The monitoring results show that the final cumulative settlement values of the surface range from-5 mm to 2 mm,which do not reach the warning value,indicating that the settlement value is within a controllable range during the construction.