邻近既有隧道的新建大断面隧道施工参数优化分析

结合大帽山隧道Ⅴ级围岩段施工参数优化的试验，通过爆破震动速度、岩体声波波速和围岩内部位移的现场监控量测工作，研究既有隧道旁新建大断面隧道双侧壁导坑法施工时岩体的损伤程度和范围，进而优化导洞的单循环进尺、爆破参数等施工参数。研究表明：推进式往复爆破作业的双侧壁导坑法开挖的隧道必然导致围岩产生一定程度的损伤、破坏，尤其是小净距隧道间的中夹岩岩墙；双侧壁导坑法开挖的大断面隧道，控制岩体的损伤程度和损伤范围是相互矛盾的，通过减少单循环开挖进尺来减少爆破震动速度，只能控制岩体的损伤范围，多次的重复爆破导致损伤岩体的损伤程度更大，极大影响围岩稳定；相反，通过适当加大单循环开挖进尺来控制损伤程度的同时，过大的爆破震动速度导致损伤范围更大，极大影响邻近既有隧道的安全运行。利用现场监测数据，通过在UDEC软件中实现的岩体各向异性爆破损伤模型，计算导洞推进式开挖全过程围岩压力的变化和既有隧道支护结构的状态，综合考虑各种因素，优化得到折中的单循环进尺。

Analysis of construction parameter optimization for new large cross-section tunnel next to existing tunnels

Based on the construction parameter optimization test of class Ⅴ surrounding rock of Damaoshan Tunnel, through the on-site monitoring work of blasting vibration velocity, acoustic wave velocity of rock mass and internal displacements of surrounding rock, the damage extent and scope of rock mass of a new large cross-section tunnel constructed by double side-wall heading excavation method next to existing tunnel was studied; and then the construction parameters such as single-cycle footage of pilot tunnel ,blasting parameters and so on were optimized. It is shown that the surrounding rock of the tunnel constructed by double side-wall heading excavation method would unavoidably be damaged in a certain degree because of repeating blasting, especially the interlaid rock wall in tunnel groups with closely-spaced. In construction of large cross-section tunnel with double side-wall heading excavation method, it is contradictory to control both damage extent and damage scope. By reducing the single-cycle footage to reduce the blasting velocity, it could only control the damage scope, however, repeated blasting would lead to a greater damage extent, greatly affecting the stability of surrounding rock. On the contrary, through appropriate increasing of the single-cycle footage to control the damage extent, the excessive blasting vibration velocity would lead to greater damage scopes, which greatly affect the safe operation of existing tunnel. Basing on the monitoring result, Therefore, in engineering practices, we should weigh the advantage and disadvantage of both solutions according to the characteristics of the actual project and to determine an optimal compromise. The research method and analysis method of this study could provide reference for the design, construction, monitoring of tunnel project under similar conditions and further theoretical research.