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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。
Applying the theory of “source and sink method”, the formula of three-dimensional additional stress generated by the soil mass loss of the double circle shield tunneling is deduced. The additional thrust force of front shield, the friction between shield shell and soil, and the distribution of total additional load caused by soil loss on adjacent pile foundation are studied. The results show that the underground pile foundation in front of the excavation face of Double Circle Shield is subjected to the compressive force and the negative additional load increases behind the excavation face to generate tension force. Meanwhile, the pile foundation near the axis depth of the Double Circular Shield The tensile stress and compressive stress are larger; the frictional force between the doubly-circular shield tunneling machine and the soil body plays an important role in the additional load, especially the additional load in the y direction; the additional load value perpendicular to the direction of the pipe sheet is more advanced But the influence range is small; the additional load in the vertical direction is small, and the additional load direction near the pile axis near the tunnel axis is opposite to the two ends, and the curve is “bow” -shaped distribution. The results of numerical simulation, centrifuge test and field comparison show that it is reliable to use analytic solution to study the effect of double circle shield tunneling on adjacent pile foundation.