深大竖井正井法施工围岩与结构力学特性分析

Analysis of the Mechanical Properties of Surrounding Rock and Structure in the Construction of Deep and Large Vertical Shaft by Top-down Method

竖井是特长隧道工程通风系统的重要组成部分,由于结构的特殊性,在竖井施工过程中其稳定性较差且安全风险高。文章依托巴陕高速公路米仓山特长隧道通风竖井工程,针对不同围岩级别,通过采用应力释放法对通风竖井的施工过程进行数值模拟,分析了竖井开挖过程中的围岩应力、衬砌位移及结构内力。结果表明:随着竖井深度的增大,竖井结构的变形和结构内力均增大,但增大的趋势趋于平缓,且满足结构安全系数的要求。为验证支护结构效果及支护参数的合理性,布置2个试验断面进行现场测试。测试结果表明:竖井围岩的压力及水压力值均较小且变化趋势平缓,该竖井的围岩为石英闪长岩,其抗压强度较大且围岩稳定性较好,在竖井开挖结束后围岩的应力已释放完毕。研究结果可为类似公路隧道深大竖井的设计与施工提供参考。

Shaft is an important part of ventilation system in super long tunnel engineering.Due to the particularity of its structure,its stability is poor and its safety risk is high in the process of shaft construction.Based on the ventilation shaft project of Micangshan super long tunnel of Bashan expressway,according to different surrounding rock grades,the construction process of the ventilation shaft was simulated by using the stress release method,and the surrounding rock stress,lining displacement and structural internal force were analyzed in the process of shaft excavation.The results show that with the increase of shaft depth,the deformation and internal force of the shaft structure increase,but the increasing trend tends to be gentle and meets the requirements of structural safety factor.In order to verify the rationality of supporting structure effect and supporting parameters,two test sections were arranged for field test.The test results show that the surrounding rock pressure and water pressure values of the shaft are small and the change trend is gentle.The surrounding rock of the shaft is quartz diorite,which has high compressive strength and good stability.After the excavation of the shaft,the stress of surrounding rock has been released.The research results can provide reference for the design and construction of similar highway tunnels.