大断面公路隧道二次衬砌受力特性模型试验

Model Test for Mechanical Characteristics of Secondary Lining of Large Cross-section Highway Tunnel

为研究大断面公路隧道运营期二次衬砌受力特征,开展室内相似模型试验,采用主动加载方式模拟隧道在运营过程中承受的围岩压力,对3车道和加宽带2种断面二次衬砌受力、变形及破坏规律进行研究。试验结果表明:1)按规范设计的大断面隧道衬砌结构在设计荷载作用下内力和变形均较小,结构具有较高的安全储备;2)衬砌各截面内力(弯矩、轴力)随围岩压力的增加呈现先慢后快的增加趋势,偏心距则呈现逐渐减小的变化趋势;3)开挖断面越大,内力控制截面越多;4)开挖断面大小对衬砌变形及破坏形态也有一定影响,断面越大,拱顶、边墙变形越大,衬砌各部位开裂荷载差异越明显,且衬砌开裂过程持续时间越长。

In order to study the mechanical characteristics of secondary lining of large cross-section highway tunnels,an indoor similar model test is carried out. The surrounding rock pressure forced on operating tunnel is simulated by active load,and the laws of internal force,deformation and failure of secondary lining of three-lane highway tunnel and broadband highway tunnel are studied. The model test results show that：（1） The internal force and deformation of secondary lining structure under loads designed by relevant codes are small; and the lining structure has large safety coefficient.（2） The section internal force（bending moment and axial force） of secondary lining increases with an accelerated speed with the increase of the surrounding rock pressure; while the eccentricity decreases gradually.（3） With the excavation area increase,the number of risky cross-section increases.（4） Excavation cross-section size also has a certain influence on deformation and failure pattern of secondary lining; the larger the excavation cross-section is,the more obvious the deformations of crown top and sidewall and the difference of cracking loading in different parts are,and the longer the process of lining structure cracking lasts.