考虑桩侧土体三维效应和地基剪切变形的隧道开挖对邻近桩基影响分析

目前就隧道开挖对桩基变形影响的解析理论研究一般基于Winkler地基模型,较少考虑地基的剪切变形和桩侧土体三维作用效应。基于Pasternak地基模型,首先推导了隧道开挖与邻近桩基相互作用的简化理论解,该解反映了地基剪切变形但未考虑桩侧土体三维作用效应。在此基础上,为反映桩侧土体三维作用效应,将其等效成集中力通过剪切层传递到桩基两侧,推导了体现三维作用效应的群桩反应表达式。将考虑与不考虑桩侧土体三维作用效应的结果进行对比,发现考虑桩侧土体三维作用效应的桩基水平位移和弯矩值更接近监测数据和离心试验数据。此外,还针对群桩影响因素进行了分析。结果表明：土体剪切变形对桩基影响不容忽视,剪切层模量越大,隧道开挖引起的桩身水平位移越小;桩径越大,桩身水平位移越小,桩身弯矩越大;桩基与隧道距离越小,桩基最大水平位移和弯矩值越大。

Influence of tunneling on deflection of adjacent piles considering shearing deformation of foundation and 3D effects of lateral soils beside piles

At present, the studies on pile deformation caused by tunneling are generally based on the Winkler foundation model. Few investigations are conducted on the shearing deformation of foundation and the 3D effects of lateral soils beside piles. Based on the Pasternak foundation model, firstly, the analytical solution of tunnel-pile interaction is derived. It reflects the effects of shearing deformation of foundation, but the 3D effects of lateral soils beside the piles are not considered. On this basis, the equivalent concentrated forces are supplied to the pile through the shear layer considering the 3D effects of lateral soils beside the piles. The expressions for lateral displacements and bending moments of pile groups are derived. The calculated results are compared with those without consideration of 3D effects of lateral soils beside the piles. It is found that the results considering effects of lateral soils beside the piles are closer to the monitoring data and centrifuge test data. In addition, the influencing factors of pile groups are investigated. The results show that the effects of soil shearing deformation on the pile deformation should not be ignored. With the decrease of foundation shear modulus, the lateral displacements of piles decrease. With the increase of the pile diameter, pile displacements decrease but the bending moments increase. The maximum lateral displacements and bending moments of piles increase with the decrease of pile-tunnel distance.