考虑桩基剪切效应的盾构开挖对邻近桩基水平向变形分析

盾构隧道开挖将引起土体卸荷,会对邻近既有桩基产生不利影响,为探究既有桩基在邻近盾构开挖下的水平向响应规律,针对已有研究的不足,提出了一种在邻近盾构开挖下能考虑桩基剪切效应的计算桩基水平向响应的简化算法。首先既有桩基被视为置于Pasternak双参数地基上的铁木辛柯梁,然后由两阶段法建立起考虑桩基剪切效应的桩基水平向变形控制微分方程,利用有限差分法解得附加荷载作用下的桩基水平向变形解析解。通过离心试验、监测数据的对比,验证了该方法的合理性。并在给定的桩土参数下,把同时考虑桩基剪切和弯曲变形的解析解与只考虑桩基弯曲变形的退化解进行对比,发现较之于欧拉–伯努利梁法,盾构对桩基扰动程度的影响,扰动越大,剪切效应体现越明显,由铁木辛柯梁法计算的位移值与弯矩值更接近实测数据。

Horizontal deformation of adjacent single pile under tunneling considering shearing effect of piles

The excavation of tunneling will release soil stress which affects the existing tunnels. To analyze the horizontal responses of the adjacent existing piles under tunneling, an analytical method is developed considering the shearing effect of piles. Firstly, the pile is considered as a Timoshenko beam resting on the Pasternak foundation, a two-parameter elastic foundation model, and by combining with the two-stage method, the equilibrium differential equation considering the shearing effect of piles is established. Secondly, the specific horizontal deformation of piles is given by using the finite difference method. Furthermore, by comparing with centrifuge test data and monitoring data, the validity of the theory is verified. Finally, a comparison is made between the results based on the Timoshenko beam and the Euler-Bernoulli beam, and its is found that the shearing effect of piles is closely related with the disturbance. The stronger the disturbance, The more obvious the shearing effect of piles. The results taking the shearing effect of piles into account are closer to the monitoring data.