地铁高架桥桩基施工对邻近构筑物的影响及控制

Influence of Pile Foundation Construction of Metro Viaduct on Neighboring Structures and Control

以长沙地铁1号线北延线上跨铁路框架桥和芙蓉北路空心板桥桥台为工程背景,构建桩基邻近既有构筑物施工三维有限元模型,分析三种钻孔顺序、地层未加固和加固情况下,桩基施工对地层、既有框架桥和桥台的受力及变形的影响。结果表明:地层沉降大致呈U形分布,沉降大小与距桩基距离成反比;排式钻孔、连续钻孔、跳桩钻孔对土体的扰动依次减弱;框架桥破坏受拉应力控制,最大拉应力出现在框架桥顶面;在采取跳桩钻孔和袖阀管地面注浆、桩基反循环钻机成孔和实时监测三种变形控制措施后,框架桥和桥台的最大沉降与未采取控制措施时相比分别减少46.7%和48.5%,其中部和两端的差异沉降分别减少31.9%和44.4%,拉应力减少64.4%。这些措施显著提高了框架桥和桥台的安全性,可保证既有线正常运营。

In this paper,Changsha metro line No.1 north extension over railway frame bridge and Furong North Road hollow slab bridge abutment was case-studied.A three-dimensional finite element model of pile foundation close to existing structures was built.The effects of pile foundation construction were analyzed on the force and deformation of the ground,frame bridge and abutment under three kinds of drilling sequences,un-reinforced and reinforced conditions of the strata.The results show the subsidence is U-shaped and the settlement is inversely proportional to the distance from pile foundation.The soil disturbance is weakened by row drilling,continuous drilling,and skipping pile drilling in order.The frame bridge damage is controlled by tensile stress,and the maximum tensile stress is at the top surface of the frame bridge.After taking the three deformation control measures of pile skipping drilling,supplemented by sleeve valve pipe ground grouting,reverse circulation drilling rig for pile foundation and real-time monitoring,compared with the pile skipping drilling without reinforcement,the maximum settlement of the frame bridge and abutment is reduced by about 46.7%and 48.5%,the differential settlement is reduced by about 31.9%and 44.4%,and the tensile stress is reduced by 64.4%,respectively.These measures significantly improve the safety of frame bridge and abutment,ensuring normal operation of the existing railway.