双线盾构施工时邻近地下管线安全性判别

研究双线盾构隧道施工时邻近地下管线的安全性判别方法。基于Winker弹性地基梁模型，考虑管土效应，建立连续管线应变与地表沉降关系式；假设管线位移与土体位移相同，建立非连续管线接头转角与地表沉降关系式；同时考虑管线老化，定义与时间相关的折减系数，建立一种通过测量地表沉降值即可判断管线安全性的方法。当管线应变或接头转角为安全允许值时，对应的地表沉降即为控制值。施工时，若地表沉降超过该值，则表明管线存在危险。该方法将不易监测的管线状态转化为可见的地表沉降。研究结果表明：预测值与实测值的对比说明了所提方法具有可靠性；双线隧道水平间距L值对地表沉降控制值的影响非常大。当L较小时，最大值出现在两隧道中轴线处；当L较大时，最大值出现在隧道轴线上方附近处；随着L的增大，最大控制值逐渐减小。

Security discrimination of adjacent underground pipelines during the construction of twin shield tunnels

This article presents a method for security discrimination of adjacent underground pipelines during the construction of twin shield tunnel. Based on Winkler elastic foundation beam model, a relationship is established between strain of continuous pipelines and surface settlement by considering pipe-soil interaction. Assuming that displacement of pipelines and displacement of soil are the same, an expression of relationship between joint angle of discontinuous pipelines and surface settlement is derived. Considering aging of pipelines, a reduction factor related to time is defined, and a method to judge the security of pipelines by measuring surface settlement is built. When the strain or joint angle of pipeline reaches the maximum safety allowable value, the corresponding surface settlement is the controlling value. The pipelines are in danger when the value of surface settlement exceeds the controlling value during the construction stage. Surface settlement monitoring data are used in this method to assess the state of subsurface pipelines and the state is not easy to be monitored. The reliability of this method has been indicated in the comparison between predicted value and measured value, and the horizontal spacing L value of twin tunnel has a great influence on the control value of surface settlement. When L is relatively small, the maximum value appears on the axis of two tunnels; when L is relatively large, the maximum value appears on the vicinity of the tunnel axis. With the increase of L, the maximum control value is gradually reduced.