松散岩堆体隧道施工中边仰坡支护效果研究

Research on Support Effect of Side Slope in Loose Rock Pile Tunnel Construction

以雅康高速日地1号隧道左线为依托工程,根据隧道地质勘探纵剖面图建立隧道洞口周围山体数值模型,并通过有限差分软件FLAC3D进行数值计算,采用强度折减法,对比分析边仰坡无支护、仅边仰坡喷锚支护以及边仰坡喷锚抗滑桩双重支护等3种工况,在隧道未开挖、隧道开挖25m和隧道开挖50m等3个阶段的安全系数及围岩应力分布情况,以评价不同边仰坡支护结构在隧道不同开挖阶段的支护效果。研究结果表明:(1)隧道尚未开挖时,边仰坡支护结构的作用并不明显,边仰坡安全系数在边仰坡有支护、无支护两种工况下均为1.07,围岩应力也无明显变化;(2)在隧道进洞开挖后,边仰坡喷锚支护结构作用明显,边仰坡安全系数提高,边仰坡表层碎石的拉应力明显减小;(3)隧道底部抗滑桩支护在未穿过坡体滑动面的情况下,支护效果有限,其增设后边仰坡安全系数并未提高;(4)隧道支护结构对边仰坡的稳定性有重要影响,良好的隧道支护对边仰坡稳定性有利;(5)隧道进洞以后,隧道的进一步开挖对边仰坡稳定性影响不大,隧道边仰坡在隧道施工过程中能否保持稳定的关键时期为隧道进洞阶段。

This paper relies on the left line of No.1Ridi Tunnel on the Ya’an-angding Expressway.According to the longitudinal section of the tunnel geological exploration,the numerical model of the mountain around the tunnel entrance is established,and numerical calculation is carried out by the finite difference software FLAC3D.The strength reduction method is used,the safety factor and surrounding rock stress distribution are analyzed and compared under 3working conditions of the side slope without support,with only shotcrete and rock bolt support and with double support in 3phases of tunnel without excavation,tunnel excavation 25mand tunnel excavation 50m.The calculation results are used to evaluate the support effect of different side slope support structures in different excavation stages of the tunnel.The results show that:(1)when the tunnel has not been excavated,the effect of the supporting structure on the side slope is not obvious.The safety factor of the side slope is 1.07under both conditions of the side slope with and without support.And there is no significant change in the surrounding rock stress.(2)When the tunnel is excavated,the side slope shotcrete-bolt support is obviously effective,the safety factor is improved,and the tensile stress of the surface gravel on the side elevation slope is obviously reduced.(3)The support effect of anti-slide pile support at the bottom of the tunnel is limited when it does not pass through the sliding surface of the slope,and the safety factor is not increased.(4)The tunnel supporting structure has an important influence on the stability of the side slope.Good tunnel support is beneficial to the stability of the side slope.(5)After the completion of tunnel portal and entrance,the further excavation of the tunnel has minor effect on the stability of the slope.The key period for the stability of the tunnel side slope during tunnel construction is during construction of tunnel portals.