双圆盾构施工引起邻近桩基附加荷载的分析

应用“源汇法”理论，推导了双圆盾构隧道土体损失产生的三维附加应力计算公式。研究了双圆盾构机正面附加推力、盾壳与土体之间的摩擦力以及土体损失在邻近桩基上引起的总的附加荷载的分布规律。研究结果表明：在双圆盾构开挖面前方地下桩基受到挤压力作用，在开挖面后方负值附加荷载逐渐增大产生拉力，同时双圆盾构机轴线深度附近的桩基部位处产生较大的拉应力和压应力；双圆盾构机与土体之间的摩擦力在附加荷载中特别是y方向的附加荷载起主导作用；垂直于管片方向的附加荷载值较推进方向大，但影响范围小；竖直方向的附加荷载较小，靠近隧道轴线附近的桩基部位受到的附加荷载方向与两端相反，曲线呈“弓”形分布。经与数值模拟、离心试验、现场实测结果对比分析，验证了应用解析解研究双圆盾构隧道开挖对邻近桩基影响是可靠的。

Analysis of additional load on adjacent pile foundation induced by double-o-tube shield tunnel construction

Based on the source-sink method, a three-dimensional additional stress formula caused by double-o-tube (DOT) shield tunnel construction soil loss is derived. The additional load caused by additional bulkhead pressure, the friction between soil and shield shell, and soil loss is added to study the total distribution of additional stress on adjacent underground pile foundation. The results show that, the additional squeeze pressure stress is caused in front of the excavation face, while the additional negative tension stress is caused in back of the excavation face. The greater pressure and tensile stresses occur near the depth of DOT shield tunnel axis. The friction between soil and shield shell plays a dominant role in total additional load, especially in the y-direction. The additional load in direction perpendicular to the segment is larger than the additional load in driving direction but has less range of influence. The additional load is small in the vertical direction, which has the opposite direction additional load near the tunnel axis compared to the additional load at each ends and its curve likes bow-shaped distribution. By the comparison with the results of numerical simulation, centrifuge experiments and field measurement, it is proved that the research on influence of DOT shield tunnel excavation on neighboring piles is reliable through analytical analysis.