Abstract

Tunnel excavations inevitably induce stress release and soil movement, which may affect the safety and serviceability of nearby existing pile foundations. The effects of tunnel construction on existing piles have been extensively investigated, but little attention was paid to lateral responses of piled foundations to tunnelling. In this study, a series of three-dimensional centrifuge model tests and numerical simulations using an advanced hypoplastic soil model were carried out to investigate the response of an existing vertically loaded 2 × 2 pile group in lateral direction due to advancement of twin stacked tunnels in dry sand. In each test, twin tunnelling was simulated three-dimensionally one after the other, with the first tunnel excavated near the mid-depth of the pile shaft and the second either next to the toe of the pile group (test ST) or below but to one side of the pile group (test SB). In addition, influences of tunnel depths and locations with respect to pile group response are investigated. The most significant lateral movement of the pile cap induced after the twin tunnelling in each test. The induced bending moment and pile deflection can be critical on completion of twin tunnels in test ST. In spite of being vertically loaded pile group, the twin tunnelling caused lateral forces (shearing forces to the pile group) in each test. The calculation charts have revealed that the tunnel depth and location relative to the pile group significantly influence induced pile cap lateral displacement and pile head bending moment.

摘要

隧道开挖不可避免地会引起应力释放和土壤运动，这可能会影响附近现有桩基的安全性和可使用性。隧道施工对现有桩的影响已被广泛研究，但很少关注桩基对隧道开挖的横向响应。在这项研究中，使用先进的发育不良土壤模型进行了一系列三维离心机模型试验和数值模拟，以研究由于双叠隧道的推进，现有垂直加载的 2×2 桩组在横向上的响应。干沙。在每个测试中，双隧道一个接一个地进行三维模拟，第一个隧道开挖在桩身中部附近，第二个隧道靠近桩组的趾部（测试 ST）或低于桩组的一侧（测试 SB）。此外，还研究了隧道深度和位置对桩群响应的影响。在每次试验中双隧道开挖后引起的最显着的桩帽横向移动。诱导弯矩和桩体挠度对 ST 试验中双隧道的完工至关重要。尽管是垂直加载的桩组，但双隧道在每次测试中都会产生侧向力（桩组的剪切力）。计算图表明，隧道深度和相对于桩组的位置对诱导桩帽横向位移和桩头弯矩有显着影响。