盾构掘进对隧道周围土层扰动的理论与实测分析

在城市环境中，如何控制地层移动以保证隧道周围临近建筑物以及地下市政设施等的安全，是设计以及施工中必须考虑的主要问题。通过对盾构施工对地层扰动的一般性状的分析认为，地层的移动在盾构隧道周围呈现区域性的不同特征，而且随工作面压力的不同，各扰动区域间的分界面发生变化。另外。由于已有地下污水管道自身具有一定的刚度，它的存在对盾构掘进引发的地层移动产生一种遮拦作用而使地层移动特征发生变化。以上海地铁二号线工程为工程背景，通过在地下污水管道周围的地层中测定地层的超孔隙水压力和土层的移动(包括地层的分层沉降以及地层在两个方向的水平位移)。研究了盾构法隧道穿越地下污水管道时盾构推进与地层移动的相关性。研究表明，在盾构掘进接近、穿越以及远离测孔区3个施工阶段，隧道周围不同区域的土层呈现出各自不同的移动特征。

THEORETICAL STUDY AND ANALYSIS OF SITE OBSERVATION ON THE INFLUENCE OF SHIELD EXCAVATION ON SOFT CLAYS AROUND TUNNEL

The main issue considered both in the design and construction in the urban environments is controlling of the ground movement to keep the safety of building adjacent to tunnel and the various underground municipal facilities. The general analysis on the ground disturbance caused by shield excavation shows that the movement of soil around the shield tunnel presents deferent regional characteristics,and the interfaces of various disturbed zones change with the magnitude of pressure on the working face. As the existing underground drainage pipe itself is of given rigidity,the sheltering will affect soils,and may change their moving characteristics. Based on the tunneling of Shanghai Metro Line No.2 in the ground beneath the drainage pipe,by surveying the pore water pressure,ground movement which includes the soil layer settlements,the horizontal soil displacements in two directions in field,the co-relationship between the ground movement and tunneling is studied. The study shows that,while the shield approaching,crossing and leaving the surveying zone,the ground movements in different zone around the Metro Tunnel present respective characteristics.