浅埋不等跨隧道围岩压力计算方法与影响规律研究

Study on calculation method and influence law of surrounding rock pressure of shallow buried unequal span tunnels

为研究不等跨隧道围岩压力,构建不等跨隧道破坏模式,基于极限上限法推导不等跨隧道围岩压力,并进行验证对比;分析不等跨隧道围岩压力分布特征,最后就相关影响因素做参数分析。结果表明:两隧道内侧围岩压力比外侧大;小跨洞竖向围岩压力大于大跨洞相应侧的值;两洞不等跨时的围岩压力比等跨时的大。随着相对跨度增大,两隧道之间的围岩压力差异增大,且大跨洞将承受更多的围岩压力。在浅埋条件下,埋深对围岩压力的影响较大。大跨隧道围岩压力随着小跨隧道埋深增大而逐渐减小;小跨隧道围岩压力则随着埋深增大而增大。竖向平均围岩压力随着两洞净距的增大呈现先增大后减小。围岩压力随GSI、m_(i)、σ_(ci)值(Hoek-Brown准则相关参数)的增大而减小。不等跨隧道应结合其相对跨度大小、两洞埋深等条件,根据所受围岩压力不同而采取不对称支护。

To study the rock pressures of the bifurcated tunnels with unequal spans,the failure modes are analyzed and the surrounding rock pressure is deduced and compared with that based on the upper-bound limit method.The pressure distribution characteristics of surrounding rock of unequal span tunnel are analyzed,and the relevant influencing factors are analyzed.The results show that the surrounding rock pressure on the inner side of the two tunnels is greater than that on the outer side.The vertical surrounding rock pressure of small span tunnel is greater than that of the corresponding side of large span tunnel.The surrounding rock pressure of the two tunnels with unequal span is greater than that of tunnels with equal span.Under the shallow burial condition,the burial depth has a great influence on the surrounding rock pressure.The surrounding rock pressure of the larger-span tunnel decreases with the burial depth of the smaller-span tunnel while the surrounding rock pressure of smaller-span tunnel increases with the burial depth.The vertical average surrounding rock pressure first increases and then decreases with the clear distance between the two tunnels.The surrounding rock pressure decreases with the GSI,m__(i) andσ_(ci),some parameters in Hoek-Brown criterion.Tunnels with unequal spans should be asymmetrically supported according to the different surrounding rock pressures in combination with their relative spans and the burial depth of the two tunnels.