局部渗水条件下深埋盾构隧道松动土压力计算模型研究

对于越江海或富水地区的深埋盾构隧道而言，长期使用过程中管片衬砌局部渗水的情况时有发生，但现有的松动土压力计算理论很少考虑局部渗水的影响。对此，以管片接缝渗水为背景，基于前人的研究进行了地层渗流场解析；以Terzaghi土拱效应分析模型为基础，考虑深埋盾构隧道的松动区形状特性和地层渗流效应，提出了局部渗水条件下深埋盾构隧道松动土压力计算模型，分析了关键参数对计算结果的影响，并与有限差分软件FLAC的模拟结果进行了对比验证。研究结果表明：渗水接缝位置离隧道拱顶越远，隧道顶部的松动土压力越大；地表水位线越高，接缝渗水对土拱的削弱效应越强；隧道顶部的松动土压力随着接缝渗水量的增加而增加；地层渗透系数越大，隧道顶部的松动土压力越小；相较于水土合算的方式，水土分算的结果中土拱效应更强；模型计算结果与FLAC模拟结果吻合良好，验证了模型的有效性。

Calculation model for loosening earth pressure of the #br# deeply-buried shield tunnel based on the influence of partial leakage

Partial leakage occurs occasionally in the undersea shield tunnels or high groundwater level shield tunnels after long-term use. Seepage effects caused by partial leakage are rarely considered in the existing theory of loosening earth pressure. Therefore, on the basis of the previous research, the seepage field is analyzed in the case of the leakage of the segment joint. This study proposes an analytical model to evaluate the loosening earth pressure based on Terzaghi’s assumption, considering the characteristics of loosening zone shape of deeply-buried shield tunnels and the seepage effects of the joint leaking. The analytical model is verified via a parametric analysis and using a FLAC numerical model. The result show that when the distance between the leaking joint and tunnel vault is high, the loosening earth pressure acting on the tunnel is high; higher surface water head leads to stronger weakening effects of the soil arch. The loosening earth pressure increases with the increasing seepage quantity of the leaking joint; the higher the permeability of the strata, the smaller the loosening earth pressure at the top of the tunnel; the separate calculation method strengthens the arching effect compared to the combining calculation of water and soil pressure; the theoretical results are consistent well with the numerical results.