双隧道对群桩影响的三维离心模型试验研究

Three-dimensional centrifuge modelling of the effects of twin tunnelling on existing pile group in expansive clay

在膨胀土地基中进行了双隧道对群桩影响的三维离心模型试验,目标地层损失比为2%,着重研究引起的地基沉降槽、附加弯矩、轴力的变化规律。试验得出:膨胀土地基中每个隧道开挖形成的地表沉降槽仍符合Peck高斯曲线,双隧道共同作用形成的沉降槽可以看作是每个隧道单独作用形成的沉降槽的叠加;两个隧道开挖引起的前后桩弯矩规律类似,最大附加弯矩均出现在拱冠附近,但存在明显的前桩遮拦效应;随着第一个隧道开挖的临近及远离,前后桩轴力会发生明显不同变化,而第二个隧道影响明显不同,附加轴力最大值约为工作荷载的10%。

A three-dimensional centrifuge modelling is conducted to investigate the effects of twin tunnel construction on existing pile groups in expansive soil with volume loss of 2.0%.Surface settlement troughs,additional bending moments and axial forces are studied.As expected,the measured settlement troughs induced by each tunnel excavation fit the Gausian distributions well.It is found that the combined settlement trough caused by twin tunneling is similar to the superposition of two individual settlement troughs by each single tunneling.Consistently,the additional bending moments of piles induced by each of the two tunnels are similar,where the maximum induced occurs near the axis of tunnel.The additional axial forces induced in front and rear piles are different due to the the first and second tunnel advancements.The maximum induced axial force is 10% of work load of the piles.