钢架岩墙组合支撑工法动态施工力学特性及其应用

京沪高速公路济南连接线浆水泉隧道全长3 101 m,最大开挖断面尺寸为19.5m×13.1m,是目前中国最长的双向八车道高速公路隧道.浆水泉隧道穿越地层主要以Ⅲ,Ⅳ级硬质灰岩为主,且施工工期紧,传统的双侧壁导坑法、CRD法等因施工工序繁琐,临时支撑多,施工效率低,无法满足工程工期需求.基于以上背景,提出钢架岩墙组合支撑分部施工工法,主要特点是中间岩墙和上台阶临时钢架组成临时支护体系,在减少临时支撑的同时,中部岩墙还能通行车辆,5个工作面可同时施工,从而实现快速施工;在此基础上,进一步运用数值计算与室内模型试验相结合的方法,对该工法的动态施工力学特性进行研究.结果表明:施工过程中,隧道上部围岩开挖的时间段是支护结构受力最不利时期,支护结构内力在此期间增长迅速,波动较大;中隔壁是支护结构中受力最不利处,其余部位结构受力对隧道施工反馈很小;影响拱顶沉降和仰拱隆起的主要因素是隧道上部围岩的开挖,影响拱脚处围岩水平收敛的主要因素是隧道下部围岩的开挖;支护结构承载和围岩变形均能够满足公路隧道施工安全需要;通过在浆水泉隧道中的实际运用表明该工法能有效提高施工效率,缩短施工工期,是一种可行的超大扁平断面隧道快速施工工法.

Dynamic Construction Mechanical Characteristics and Application of Combination Support Method of Steel Frame and Rock Wall

The Jiangshuiquan Tunnel of Jinan that connects to the Beijing-Shanghai Expressway is 3 101 m in length, and the maximum excavation section is 19.5 m×13.1 m. It is the longest expressway tunnel in China and has eight lanes. The Jiangshuiquan Tunnel mainly passes through hard limestone strata of grades Ⅲ and Ⅳ, and the construction period is tight. The traditional double-side-drift and center cross diagram methods cannot meet the needs of this project due to complicated construction procedures, much temporary support, and low construction efficiency. Based on this background, a combination support method of a steel frame and rock wall is proposed. This method is mainly characterized by a temporary support system composed of a mid-rock wall and a temporary steel frame of upper steps. Not only can temporary support be reduced, but vehicles can also pass through the mid rock wall, and five working faces can be constructed simultaneously to achieve rapid construction. On this basis, the dynamic construction mechanical characteristics of this method were further studied by performing an indoor model test combined with numerical calculations. The results show that the excavation period of the surrounding rock in the upper part of the tunnel is the most disadvantageous period for the supporting structure. During this period, the internal force of the supporting structure increases rapidly and fluctuates considerably. The middle wall is the most disadvantageous part of the supporting structure, and the feedback of the structural force in the other parts to the tunnel construction is very small. The main factor affecting the settlement of the vault and the uplift of the inverted arch is the excavation of the surrounding rock in the upper part of the tunnel. By contrast, the main factor affecting the horizontal convergence of surrounding rock at the arch foot is the excavation of surrounding rock in the lower part of the tunnel. The bearing capacity of the supporting structure and the deformation of surrounding rock can meet the safety needs of highway tunnel construction. Finally, practical application in the Jiangshuiquan Tunnel showed that this construction method can effectively improve construction efficiency and shorten the construction period; hence, it is a feasible fast construction method for super-large flat section tunnels.