大断面单洞四车道公路隧道结构设计与施工方案探讨

龙头山隧道为双向分离式单洞四车道高速公路隧道，隧道最大开挖宽度21．1m，是目前国内单洞开挖跨度最大的隧道之一。本文采用工程类比法对该隧道的结构支护参数进行了多方案的比选，针对不同围岩地质区段和两侧已有的地下油库建筑，提出了地表注浆、反压护拱、双侧壁导坑开挖和微震动爆破施工等方法。应用有限元数值方法，结合不同的施工步骤，对隧道支护结构和围岩的稳定性进行了模拟分析，分析结果表明本文所确定的支护参数和施工方案安全可行。

Discussion About Structural Design and Construction Schemes for Four-Lane Section in Each Separated Hole of Highway Tunnels

Longtoushan Tunnel is an expressway tunnel with four lanes in each of the two separated holes on both-sides. It's largest excavation width is 21.1 m.So far,it is one of the single-hole tunnel which has the largest excavation width in the country. Using the method of engineering analogy, the structural timbering parameters of several different schemes are compared. Aiming at the different surrounding rock geological sections and the oil storeroom along the two sides which has been constructed underground,some construction methods are put forward,such as the slurry injection from the ground;erecting the tunnel first,then filling the earth;excavating by double-sides-wall drift;small-shaking dynamite construction method,and so on. Through the FEA(Finite Element Analysis),and combining with the different construction procedures,the timbering structure and the stability of the wall rock are stimulated and analyzed. The results show that the timbering parameters and the construction scheme are safe and feasible.