隧道开挖对周围土体及桩基影响的试验研究

Test Study on Tunnelling-induced Soil Movements and Pile Responses

通过离心机试验研究了粘土中隧道开挖引起的土体瞬时和长期沉降.对不同的隧道与桩间距情况进行了3组离心机试验,研究隧道开挖对桩基的瞬时和长期影响.试验结果表明,高斯曲线法计算的土体瞬时沉降与试验值比较吻合,而计算的长期沉降低估了地表沉降的影响范围.隧道开挖引起的桩身最大轴力和弯矩都发生在隧道起拱线附近,而且桩基反应都是随着隧道与桩间距的增加而减小.随着时间的增加,地表沉降、桩身弯矩和侧向变形都有显著增加,所以隧道开挖的长期影响不容忽视.

Centrifuge model tests have been conducted to study the effects of tunnelling-induced soil movements and single pile responses in both short and long terms in clay. Three tests are performed to evaluate the effects of distance between pile and tunnel on pile responses due to tunnel excavation. The results reveal that the surface settlement calculated by Gaussian curve in short term show agreement with centrifuge test. However, Gaussian curve underestimates the measured settlement in long term at the far end of the ground surface. Both maximum induced pile axial force and bending moment take place at the tunnel spring elevation. Inaddition, the pile responses decrease with an increase in pile- to-tunnel distance. However, the induced surface settlement, pile bending moment and deflection continue to increase for some time after the completion of tunnel excavation. So the effects of tunnelling in long term cannot be ignored.