关键词: 新建隧道, 上穿隧道施工, 既有隧道, 隧道隆起, 解析解

Abstract: New tunnel crossing over existing tunnel will inevitably change the already balanced ground stress field and cause ground stress relief, which will result in longitudinal heave of existing underlying tunnel. An analytical method is proposed to assess the longitudinal displacement of the existing tunnel subjected to above-crossing tunneling. The existing tunnel is simplified to be Euler-Bernoulli beam resting on the Pasternak foundation model. Two-stage analysis method is adopted to analyze this problem. First, the vertical distributed unloading load induced by the construction of above-crossing tunnel is computed by Mindlin′s solution. Second, equilibrium differential equation is established under the corresponding vertical distributed load due to unloading and it is solved numerically based on the finite difference method. The applicability of the presented method is validated against two well-documented case histories. A consistent trend between the measurements and predictions is observed. It means the proposed method can be reasonably reflect the law of the longitudinal displacement of existing tunnel subjected to above-crossing new tunnelling in close distance.