导洞施工中群洞效应对地表沉降的影响

导洞为PBA工法进行大型地铁车站施工的主要临时结构,具有距离近、个数多的特点。为研究多个导洞施工的群洞效应,采用三维数值计算模型,讨论了地表沉降影响随导洞的施工顺序、工法、施工间隔和台阶长度等因素的变化规律。以地表沉降为指标,采用正交试验方法进行4因素3水平的试验研究。极差分析结果表明,导洞的施工工法是影响地表沉降的最主要因素,而导洞的施工工序影响较小。导洞的施工间隔和台阶长度对地表沉降的影响并非单调函数,有最优值的存在。因此,可通过优化导洞间施工间隔和台阶长度来降低地表沉降。

Influence of Group Tunnel Effect on Subsidence of Ground Surface in Pilot Tunnels Construction

Pilot tunnels, the main temporary structures in large subway station construction by PBA method, are characterized by close distance and large number. In order to study the group tunnel effect of these tunnels, 3D numerical computation model was used to discuss the law how the influence on ground surface subsidence changes with the pilot tunnels＇ construction sequence, method, and interval and bench length. Taking ground subsidence as the indicator, 4-factor ＆ 3-level experimental research was conducted by orthogonal tests. The result of the range analysis shows that the construction method of pilot tunnels is the main factor affecting ground surface subsidence and the construction process thereof has the minor impact; the effect of the construction interval and bench length on the subsidence is not a monotonic function and there exists a optimal value; hence, the optimization of the tunnels＇ construction interval and bench length may reduce the ground surface subsidence.