大断面隧道装配式约束混凝土施工体系研究与应用

Research and Application of Fabricated Confined Concrete Construction System for Large Cross Section Tunnel

为解决大断面隧道软弱围岩控制难题及人力施工效率低、安全性差的问题,结合约束混凝土支护研究成果,研发拱架智能安装系列设备、装配式约束混凝土拱架(FCC拱架)及相应的配套装置,形成大断面隧道装配式约束混凝土施工体系。开展FCC拱架机械施工过程力学模拟试验,对拱架机械施工过程中的变形及受力进行实时监测,明确拱架机械施工过程力学特性,提出增设肩部节点区抗弯护板的加强措施,进行装配式约束混凝土支护机械化施工现场试验,分别对隧道围岩收敛变形、围岩与初支接触压力、加强后的拱架内力分布特征与规律进行了研究。结果表明:在FCC拱架自重及机械施工双重影响下,拱架肩部节点区变形产生突变,发生明显的应力集中,为受力变形关键部位;加强后的FCC拱架现场举升安装过程中未见有明显的变形;现场试验段围岩偏压现象明显;上台阶围岩变形及受力呈现三阶段波动增长,以拱顶及拱肩部位波动最为强烈;拱架受力整体呈现"上大下小"的特点,最大应力值出现在拱顶外侧,其次左拱肩部位;机械化施工能够有效提高施工效率及装配化水平,保障施工安全可靠,有效控制大断面隧道围岩变形,可为类似工程建设提供借鉴。

This study was conducted to solve the difficulty of controlling the soft surrounding rock of a large section tunnel and the problem of low efficiency and poor safety during the construction process. Based on the research achievements of the confined concrete arch support, a series of intelligent installation equipment, fabricated confined concrete arches（FCC arches）, and corresponding supporting devices was developed, and the FCC system of a large section tunnel was formed. A mechanical simulation test of the machine assembly construction process of the FCC arch was carried out. The deformation and stress of the arch in the construction process were monitored in real time, the mechanical characteristics of the construction process of the arch were clearly defined, and the strengthening measures, including the anti-bending plate in the shoulder area, were put forward. The field experiments on the mechanized construction of fabricated confined concrete support were carried out, and the characteristics and laws of the convergence and deformation of the surrounding rock, the contact pressure of the surrounding rock and the initial support, and the internal force distribution of the arch were determined. The results showed that under the combined influence of self-weight and mechanical construction of the FCC arch, the deformation value in the shoulder area of the arch, which is the key part of the stress and deformation, suddenly changes, and the stress concentration situation is obvious; there is no obvious deformation in the process of the installation of the reinforced FCC arch. In the field test section, the eccentric compression phenomenon was obvious. The deformation and stress of the upper stage surrounding rock exhibit three stages of fluctuating growth, with the most intense fluctuation in the vault and shoulder area; the stress of the arch was characterized by ＂bigger on the upside and smaller on the downside＂, and the maximum stress value appeared on the outside of the vault, followed by the left arch shoulder position. The mechanized construction could effectively control the deformation of surrounding rock of the large section tunnel, improve the effectiveness and fabrication level, and guarantee security and reliability of the construction process, which can provide a reference for similar projects.