【摘要】 利用有限元强度折减法结合基于有限差分原理的FLAC软件,探讨了隧道设计计算过程中初衬和二衬的计算问题以及隧道开挖的应力释放问题,并以黄土隧道为例探讨研究不同应力释放率以及不同初衬和二衬厚度情况下隧道的受力特征,计算围岩安全系数以及二衬安全系数,得出了以下结果:一是利用FLAC软件计算中的不平衡力来控制隧道开挖过程的应力释放是合适的与可行的;二是初衬作为隧道围岩的加固圈将承受较大荷载和产生较大的变形,初衬必将进入弹塑性状态;二衬作为隧道的强度储备或者承受不大的荷载,二衬视作弹性杆件可按结构力学的方法确定安全系数;三是如果初衬后围岩安全系数大于1.30,可以认为围岩和初衬都是稳定的,二衬作为安全储备;如果围岩安全系数在1.30～1.15之间或围岩为粘弹塑性材料时,表明二衬将承受一定荷载;如果初衬后围岩的安全系数小于1.15～1.20,则认为初衬不足,不能保证施工安全。最后建议对二衬后的围岩安全系数取1.3,二衬结构安全系数对无抗裂要求的混凝土衬砌取1.4,钢筋混凝土衬砌取1.35。两者综合的安全系数大约在1.8左右以供参考。更多还原

【Abstract】 Combining the method of finite element strength reduction with FLAC software,this paper researches the problems of calculation of the initial lining and the secondary lining and the stress release during the tunnel design and calculation process,and the force characteristics of a tunnel in the case of different stresses release rates and different initial and secondary lining thickness by taking the example of a loess tunnel.After calculating the safety factors of surrounding rock and secondary lining,this paper draws the following conclusions: Firstly,with the use of the unbalanced force in FLAC software to control the stress release during the tunnel excavation process is practicable and in line of reality;Secondly,the initial lining as the reinforcement ring of surrounding rock will bear a greater load and have a greater deformation,so the initial lining will enter the plastic state,and for the secondary lining as a strength reserve of the whole tunnel or to bear a little load.If the secondary lining is taken as a flexible rod the method of structural mechanics may be used to determine the safety factor;Thirdly,if the safety factor of surrounding rock is greater than 1.30 after initial lining,it can be considered that the surrounding rock and the initial lining are stable,taking secondary lining as a safety reserve;and if the safety factor is less than 1.30,it shows that the secondary lining should be made to withstand a certain load;and if the safety factor is less than 1.15~1.20,it is concerned that the initial lining is not enough to ensure construction safety.Finally,it is recommended that the safety factor of the surrounding is taken as 1.3 after the secondary lining,and structural safety factor of the secondary lining without requirement on crack-free concrete lining is taken as 1.4,and for reinforced concrete lining 1.35.As a reference,the integrated safety factor for these two is 1.8 or so.更多还原