隧道穿越泥石流堆积体及活动断裂施工关键技术

新建铁路成兰线红桥关隧道浅埋穿越泥石流堆积体及活动断裂,施工中出现洞周岩土体失稳而向洞内滑移、地表开裂和支护体系异常变形破坏等工程问题。本文从地质条件及开挖效应、地下水和地层偏压等方面进行分析,针对性实施“先固后钉法”施工关键技术,即在洞室开挖前施作群桩预加固形成半封闭支护结构,在初期支护后施作复合土钉形成补强支护结构。该技术改善了围岩条件,提高了支护体系的整体性,充分协调和控制了围岩及支护体系的变形,确保了隧道的施工安全。

Key Technology of Tunnel Construction Through Debris Flow Accumulation Body and Active Fault Zone

Hongqiaoguan Tunnel of Chengdu-Lanzhou Railway passes through debris flow aceumulation body and active fault zone,in the process of tunnel construction,there are some engineering problems,such as the instability of rock and soil around the tunnel and sliding towards the tunnel,the surface cracking and the abnormal deformation and failure of the support system.In the paper,the key construction technology of"firming before nailing"was implemented in aspects of analyzing the geological conditions and excavation efect,groundwater and stratum bia,in other words,construeting a semi-closed supporting structure by pre-reinforcement of pile groups before excavation of the cavern,and forming a reinforced supporting structure by applying composite soil nails after initial support.The technology improves the surrounding rock conditions and the integrity of the supporting systerm,fully coordinates and controls the deformation of the surrounding rock and the support system,and ensures the construction safety of the tunnel.