隧道开挖引起邻近单桩水平反应分析

隧道开挖会降低邻近桩基承载力，如何更为合理评价桩基水平附加响应是需要解决的问题。基于Pasternak双参数地基模型和三折线弹塑性荷载传递模型，采用两阶段分析法，并考虑侧向土体作用及地基土层的非均质特性，提出了更符合实际的单桩水平反应简化分析方法。通过与Winkler地基梁法及边界元法的对比分析，验证了方法的合理性。结合对单桩水平反应的多种影响因素进行参数分析，通过各因素相应的修正系数来对基准工况中单桩最大水平反应进行修正，得到计算工况中单桩的最大水平位移和最大弯矩。分析结果表明，桩基水平位移计算时可忽略侧向土体作用，而弯矩计算时应予以考虑；桩基计算工况的最大水平位移 最大弯矩 与平均地层损失比 呈现线性关系，而与隧道半径R、隧道轴线深度H、桩距隧道中心线距离x及桩身柔度系数 均呈现非线性关系。

Lateral response of adjacent single pile due to tunneling

Tunnel excavation can reduce the bearing capacity of adjacent pile foundation. How to accurately evaluate the additional pile responses is a problem yet to be solved. A simplified analytical method is developed based on a Pasternak-type two-parameter elastic foundation model and a three polyline-elastic-plastic load transfer model; a two-stage analytical method is used and the effect of lateral soil and heterogeneity characteristics of soil are considered. The validity of the proposed method is verified by the comparative analysis of the results obtained from proposed method, Winkler foundation beam method and boundary element method. Combining with parametric studies of the influencing factors of lateral response of a single pile, correction coefficients are used to correct the maximum lateral response of a single pile in the baseline engineering case, the maximum horizontal displacement and the maximum bending moment of a single pile under the calculation working condition are obtained. The results indicate that in calculating the horizontal displacement, the effect of lateral soil can be ignored, while it should be considered in calculating bending moment. The average ground loss ratio is linearly related to while it presents a nonlinear relationship with tunnel radius R, tunnel axis depth H, distance from the center line of the tunnel x and pile flexibility coefficient .