内出进洞方式对浅埋偏压隧道洞口段围岩稳定性影响研究

A study of tunnel surrounding rock stability of shallow and unsymmetrical loaded portal section with excavation sequences from inside

厦蓉线水都高速平寨隧道左洞洞口受施工条件、浅埋和偏压等因素的影响,采取了中横洞内出的进洞方法。现场监测成果表明施工取得了良好的效果。为研究该进洞方式对洞口浅埋偏压段围岩稳定性的影响,利用FLAC3D程序对平寨隧道施工过程进行三维仿真分析,比较中横洞内出和正面开挖两种进洞方式下左洞洞口围岩变形和应力变化情况,结果表明中横洞内出方案对近洞口约24m范围内围岩影响较小,为较优方案。

The Pingzhai tunnel is located in the Shuidu Highway of the Xia-Rong Line.The middle horizontal adit is used to enter the left tunnel portal,which is affected by construction conditions,shallow buried and unsymmetrical loadings.Field measurements show that good effect has been achieved in the construction.To examine the effect of this excavation sequences on surrounding rock stability of shallow buried and unsymmetrical loaded portal section,an analysis of 3-D simulation in the excavation process of the Pingzhai tunnel is conducted by using the FLAC3D software.Comparing the middle horizontal adit excavation sequence with the common excavation sequence,the changes in deformation and stresses of surrounding rock of the Pingzhai tunnel in different excavation sequences are obtained.The results show that deformation and stresses of surrounding rock within 24 m from the portal are less those under middle horizontal adit excavation sequence,and the method is better.