关于复合式衬砌整体计算模型的思考

复合式衬砌传统计算方法常忽略初期支护内力计算及其安全性检验,二次衬砌所承担的围岩荷载根据围岩条件进行经验确定。针对其不足,提出适用于复合衬砌的整体计算模型,并通过实例计算分析传统计算模型与整体计算模型下内力产生差异的原因。围岩与初支间接触的模拟需考虑其法向及切向约束作用。软弱围岩对初衬的最大剪切约束力与围岩的黏聚力、内摩擦角及两者所传递的法向压力有关,当围岩与初衬间的剪切力大于最大剪切约束力后,软弱围岩所能发挥的剪切约束与剪切位移、摩擦系数及两者所传递的法向压力有关。因防水板的设置,初衬与二次衬砌仅需考虑其法向约束作用,以仅受压弹簧模拟围岩与初衬及初衬与二次衬砌间的法向约束,可较为真实地模拟接触受压后方能传递压力的特性。传统计算模型下,围岩荷载承担比例的增加对衬砌内力分布形式影响较小,衬砌内力值与围岩荷载基本成同比例变化;整体计算模型下,围岩荷载在初衬与二次衬砌间进行自适应分配,衬砌所受荷载大小及分布形式与传统计算模型下的荷载具有较大差异,因此内力大小及分布形式也随之发生变化。

An Approach to Integral Calculation Model of Composite Lining

The traditional calculation method of composite lining often ignores the calculation of internal force and the safety in the primary support,and the load of surrounding rock loaded by the second lining is empirically decided based on the surrounding rock condition. As for its deficiency,the integral calculation model of composite lining is put forward and the causes for the difference of internal forces derived from the traditional calculation method and the integral calculation method are discussed in detail through examples. The normal and tangential constraints between the surrounding rock and the primary support should be included in simulation. The maximum constraint shear force in the weak surrounding rock is related to the cohesion,the internal friction angle and the normal pressure transmitted by the surrounding rock. After the shear force between the surrounding rock and the primary support surpasses the maximum constraint shear,the constraint shear in the weak surrounding rock is related to the shear displacement,the friction coefficient and the normal pressure transmitted between them. Due to the setting of the waterproof plate,the normal restraint between the primary support and the secondary lining should only be considered. The compression-only spring to simulate the contact between the primary support and the surrounding rock and that between the primary support and the second lining can well demonstrate that the transmission of force only occurs after contact compression. Under the traditional calculation method,the internal force distribution in lining changes little while the valueof it changes in proportion to the load ratio of the surrounding rock. Under the integral calculation model,as the load of surrounding rock is distributed automatically between the primary support and the secondary lining,the value and the distribution of load generated by the lining are quite different from those in the traditional calculation model,resulting in the changes of the value and distribution of the internal force of lining.