考虑复合衬砌层间接触效应的衬砌结构力学特征

Mechanical Characteristics of Lining Structure Considering the Contact Effect between Composite Lining Layers

为了研究防水板对复合式衬砌结构力学特征的影响机制,以实际工程为依托,采用FLAC3D有限差分软件内置的Interface接触面单元模拟防水板引起的层间接触效应,建立数值仿真模型并与荷载结构模型进行对比,分析了二衬在不同排水率下的内力及形变特征,并探究了二衬各设计因素对其安全性的影响规律。结果表明:在初支与二衬间设置接触面单元来模拟防水板引起层间接触作用的地层结构模型可靠性较高;防水板的存在导致初支与二衬无法协同受力,复合衬砌层间出现应力突变现象,二衬具有挤压或脱离初支的形变特征,且受挤压部位的层间界面将产生错动滑移;依托隧道断面最小安全排水率为0.66,隧道排水率低于0.8时衬砌最不利截面均位于拱脚附近;相比于增大二衬厚度或混凝土强度等级,优化衬砌结构断面形状更能提高其水压承载能力,且优化衬砌断面形状后的二衬通过增大厚度或混凝土强度来提高其水压承载能力的效果高于优化前。

In order to study the influence mechanism of waterproof board on the structural mechanics characteristics of composite lining,relying on the actual project,the interface contact surface element embedded in FLAC3D finite difference software was used to simulate the interlayer contact effect caused by waterproof board,and the numerical simulation model was established and compared with the load structure model.The internal force and deformation characteristics of the secondary lining under different drainage rates were analyzed,and the impact of various design factors on the safety of the secondary lining was explored.The results show that the reliability of the stratum structure model is high by setting the contact surface element between the primary support and the secondary lining to simulate the interlayer contact effect caused by the flashing plate.The existence of the waterproof board causes the primary support and the secondary lining to be unable to cooperate with each other,lead to the occurrence of stress mutation between composite lining layers,the secondary lining has the deformation characteristics of extrusion or separation from the primary support,and the interlayer interface of the squeezed part will produce dislocation slip.The minimum safe drainage rate of this tunnel section is 0.66,when the drainage rate of the tunnel is lower than 0.8,the most unfavorable section of the lining is located near the arch foot.Compared with increasing the secondary lining thickness or concrete strength grade to improve its water pressure bearing capacity,optimizing the section shape of the lining structure is more effective,and the effect of improving the water pressure bearing capacity of the secondary lining after the optimization of the structural section shape is higher than that before the optimization by increasing the thickness or the strength of the concrete.