浅埋暗挖隧道下穿既有构造物施工技术

Construction Technology for Shallow Overburden Tunnel Under-crossing Existing Structures

在浅埋暗挖隧道下穿既有构造物施工过程中,隧道的开挖极易引起地表及构造物的沉降变形,给隧道施工带来极高的安全隐患。以龙泉山隧道下穿张万沟大桥工程为例,鉴于张万沟大桥桩基础底与龙泉山隧道顶间距较小,在不采用一定的加固技术条件的前提下直接采用常规爆破开挖支护施工将致使建筑物产生附加应力和变形[1],从而影响建筑物的正常使用和安全,因此,隧道在下穿过程前必须采用预先加固措施。介绍了该工程通过地震波反射法超前地质预报,采用超前帷幕注浆、大管棚双重预加固,实施上下台阶光面爆破施工技术有效控制了地表及隧道拱顶沉降的全过程,所取得经验可为类似工程提供参考。

Excavation of shallow overburden tunnels under-crossing existing structures can easily cause settlement and deformation of ground surface and the structures,which leaves great safety hazards to tunnel construction.Longquanshan Tunnel under-crosses Zhangwangou Bridge,and the distance between pile foundation of Zhangwangou Bridge and the top of the tunnel is relatively small.Additional stress and deformation on the structures occur when conventional blasting excavation and support method is applied without taking reinforcement measures,then safe and normal operation of the structures will be disturbed,so the structures must be pre-reinforced before excavation starts.This paper introduces how the settlement of the surface and tunnel arch is effectively controlled on Longquanshan Tunnel which under-crosses Zhangwangou Bridge applying seismic reflection geological forecasting method,advanced curtain slurry,large pipe shed pre-reinforcement measures,as well as upper and lower step smooth blasting method.The experiences obtained provides reference for similar projects.