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以大西客运专线忻州隧道三七微台阶法开挖为工程背景,采用FLAC3D模拟分析施工过程中初期支护结构的受力特性,并与锚杆轴力和喷射混凝土应力的现场测试结果进行对比分析,最后结合型钢混凝土截面受力计算方法,评价型钢混凝土初期支护结构的安全性。研究结果表明:1型钢混凝土主要承受压应力,且沿隧道中线呈轴对称分布,最大压应力出现在拱腰位置,而拱脚处局部承受拉应力,为施工中的薄弱部位,喷射混凝土应力实测值相对计算值偏小,但分布规律与计算值吻合性较好;2隧道系统锚杆主要承受拉力作用,最大拉力在锚杆1 m位置,沿隧道轮廓从拱顶到拱脚递减,且计算值略大于实测值,两者分布规律一致;3型钢混凝土结构安全系数从隧道拱顶到拱脚依次递增,且同一部位轴力安全系数小于弯矩安全系数,轴力安全系数最小值为3.86,满足规范要求,可适当增大钢拱架支护间距或减小喷射混凝土强度。
Taking the engineering construction of Sanzhou micro-terrace excavation in Xinzhou tunnel on the West-west Passenger Dedicated Line, this paper uses FLAC3D to simulate and analyze the mechanical characteristics of the initial supporting structure during construction, and compares it with the on-site test results of bolt axial force and shotcrete stress Finally, combined with the calculation method of the section strength of SRC, the safety of initial support structure of SRC was evaluated. The results show that: 1 steel reinforced concrete is mainly subjected to compressive stress and distributed axisymmetrically along the middle of the tunnel, the maximum compressive stress appears in the position of arch and waist, while the tensile stress is locally absorbed in the arch foot. For the weak parts in construction, the measured stress of shotcrete The value of the relative value of the calculated value is small, but the distribution law is in good agreement with the calculated value. 2 The bolt of the tunnel system is mainly subjected to the pulling force. The maximum tensile force decreases from the arch to the arch along the tunnel profile at 1 m of the bolt. The safety factor of 3 type steel reinforced concrete gradually increases from the arch to the arch of the tunnel, and the safety factor of axial force in the same part is less than the safety factor of bending moment, the minimum value of the safety factor of axial force is 3.86, Meet the specifications, may be appropriate to increase the spacing of steel arch support or reduce the intensity of shotcrete.