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首先介绍了传统设计方法的优缺点,并分析了数值极限分析方法在隧道设计中的可行性。给出了隧道围岩、初期支护和二衬安全系数计算方法,对隧道结构安全性评价提出了量化指标。指出了该方法不仅可计算每个施工步的安全系数还可通过安全系数优化设计方案,同时考虑隧道的安全性和经济性。其次强调了隧道初期支护的重要性,认为初期支护在保证隧道施工安全中起到了关键作用,传统计算方法将初期支护视为弹性材料是不合理的。将初期支护视为弹塑性材料,认为初期支护作为围岩加固材料并承担主要围岩压力,二衬视为安全储备承担较少荷载,且初期支护和围岩最先进入塑性阶段。最后通过工程案例说明了数值极限分析方法在土体隧道设计中的应用。
Firstly, the advantages and disadvantages of traditional design methods are introduced, and the feasibility of numerical limit analysis in tunnel design is analyzed. The calculating methods for the surrounding rock, initial support and safety factor of the second lining are given, and the quantitative indexes for the safety evaluation of the tunnel structure are proposed. It is pointed out that this method can not only calculate the safety factor of each construction step, but also optimize the design scheme by the safety factor, taking into account the safety and economy of the tunnel. Secondly, the importance of initial tunnel support is emphasized. It is considered that initial support plays a key role in ensuring the safety of tunnel construction. It is unreasonable to regard initial support as elastic material by traditional calculation methods. The initial support is regarded as elastic-plastic material. It is considered that the initial support is used as the surrounding rock reinforcement material and assumes the pressure of the main surrounding rock. The second lining is assumed to bear less load for the safety reserve, and the initial support and surrounding rock first enter the plastic phase. At last, the application of numerical limit analysis method in soil tunnel design is illustrated through engineering case.