并行隧道顺序开挖围岩及衬砌承载行为分析

Analysis on Bearing Behavior of Surrounding Rock and Lining of Parallel Tunnels with Sequential Excavation

双孔大跨度并行马蹄形隧道施工过程中围岩及衬砌的承载行为对施工的安全性有着重要影响。本文通过对不同围岩级别及净距工况下的双孔大跨度并行马蹄形隧道开挖过程进行数值模拟,研究围岩及中间岩柱受力状态和衬砌应力分布规律。研究表明:(1)该类型隧道在开挖过程中,拱脚处最易发生剪切破坏;(2)净距大小对中间岩柱应力状态影响较为明显;(3)后建隧道会造成先建隧道靠近中间岩柱侧上方的衬砌应力增大,在实际施工过程中应当重点监测;(4)Ⅴ级围岩的洞间距宜大于1.5倍洞径,Ⅳ级围岩的洞间距宜大于1.0倍洞径。本文的研究可为类似工程设计提供一个参考。

Controlling the stress state of surrounding rock and lining in twin-parallel,large span,small spacing and horseshoe-shaped tunnels during sequential excavation can guide the safety of construction. Twenty-five numerical simulation models were established about twin-parallel large span and horseshoe-shaped tunnel by FLAC3 D,and the stress state distribution of the middle rock pillar and lining has been obtained. The result showed that:( 1) At arch springing there was most likely to happen the shear failure during excavation;( 2) The spacing size affected the stress state of middle rock pillar;( 3) The lining stress of the existing tunnel's upper side near the middle rock pillar enlarged with sequential excavation,so we should focus on its monitoring in the actual construction process;( 4) The spacing should be more than 1. 5 times the hole diameter with level Ⅴ surrounding rock as possible,and be more than double the hote diameter with level Ⅳ surrounding rock. This study provides a reference for similar projects.