基于Kerr地基模型的基坑开挖引起下卧既有隧道受力变形

Deflections of Adjacent Underground Tunnel Induced by Excavation Based on Kerr Foundation Model

基坑开挖导致的土体卸载作用会引起邻近下卧既有隧道隆起变形,甚至会干扰隧道的正常运营.提出了一种基坑开挖引起下卧隧道纵向变形的简化计算方法,将隧道简化成无限长Euler-Bernoulli梁搁置在三参数的Kerr地基模型,提出了剪切层弯矩的计算假设,利用有限差分法并结合隧道两端的边界条件得到隧道纵向变形差分解.结果表明:与既有文献中有限元数据和实测数据对比,证明了Kerr地基模型的准确性;与将隧道简化成Euler-Bernoulli梁搁置在Pasternak地基模型相比,Kerr地基模型更具有优越性.地基模量、隧道埋深的增大会引起隧道纵向位移及内力的减小;隧道刚度的增大会引起隧道纵向位移的减小但会引起隧道内力的增大.

The soil unloading effect caused by the adjacent excavation will influence both the uplift and the deformation of the adjacent existing tunnel, and even interfere with the normal operation of the tunnel. A simplified calculation method for the longitudinal deformation of the underlying tunnel caused by foundation pit excavation is proposed. The tunnel is simplified into an infinitely long Euler-Bernoulli beam resting on a three-parameter Kerr foundation model. The difference method is combined with the boundary conditions at both ends of the tunnel to obtain the longitudinal deformation difference decomposition of the tunnel. The accuracy of the proposed method is proved by comparing it with the finite element simulation method and some cases study. Compared with the tunnel simplified as the Euler-Bernoulli beam which is placed upon the existing Pasternak foundation model, the Kerr foundation model has more advantages. As the elastic modulus of soil mass and the depth of tunnel axis increase, the longitudinal deflection and the inner force of the tunnel will decrease. The inner force of the tunnel will increase with the increment of the stiffness of the tunnel.