富溪偏压连拱隧道围岩与支护结构变形和受力特征分析

ANALYSIS OF DEFORMATION OF SURROUNDING ROCK AND STRESS CHARACTERISTICS OF SUPPORTING STRUCTURE OF FUXI TWIN TUNNEL

铜黄高速公路汤屯段富溪偏压连拱隧道,长623m,洞口段围岩为全风化变质砂岩,呈散体结构,不能自稳。洞口段左侧埋深较右侧大,存在明显的偏压。隧道施工采用三导洞法进行,施工期间对洞口段三导洞、正洞的多个断面进行现场监控量测。通过分析监测数据,可得围岩变形与支护结构受力特点。监测结果表明:中导洞形成后,浅埋侧导洞先行施工,其围岩变形较深埋侧导洞要大;正洞施工期间,深埋侧拱顶下沉较浅埋侧大,深埋侧水平收敛呈扩张趋势,浅埋侧水平收敛呈收缩趋势,中隔墙呈向浅埋侧偏移趋势;无论初期支护还是二次衬砌,其围岩压力、混凝土内应力均是深埋侧大,由于整体衬砌有向浅埋侧运动趋势,钢支撑所受应力在浅埋侧较大。分析结果对富溪偏压隧道施工具有指导意义,对类似隧道的设计、施工和研究具有借鉴和参考价值。

Fuxi twin tunnel in Tangkou—Tunxi section of Tongling—Huangshan Expressway is eccentric compressed with the length of 623 m.Weathered meta sandstone at the portal is loosely structured and unstable.The portal is apparently eccentric with the left side buried deeper than the right side.Three pilot tunnel method has been applied for tunneling.During the construction,site monitoring and measurement have been conducted for various cross sections of the three pilot tunnels and the main tunnel.Data have been studied and analyzed.Deformation of the surrounding rocks and stress of the supporting structures have been noted.Monitoring result shows that,after the heading-through of the central pilot tunnel,construction is organized firstly on the pilot tunnel of the shallow-buried side.It is envisaged that the deformation of the surrounding rocks of the shallow buried section is greater than that of the deep buried one.During the construction of the main tunnel,arch crown subsidence at the deep buried section is greater than that of the shallow buried section.The horizontal convergence at the deep buried section tends to be expansive while that at the shallow buried one shrinking,which causes the movement of the mid-board towards the later section.Initial supporting and secondary lining also envisages the greater pressure of the surrounding rocks as well as the greater internal stresses of the concrete at the deep buried section.As it has the tendency of moving towards the shallow buried section during the integral lining,the steel shotcrete at the section bears greater stress.This analysis offers some technical assistance to the construction of Fuxi eccentric compressed tunnel as well as some references for the design,construction and research of the similar engineering.