组合缺陷影响下衬砌结构受力特征分析

Analysis of stress characteristics of lining structure under the influence of combined defects

以云南山区某2车道公路隧道为依托,建立基于围岩压力修正的荷载-结构模型。通过引入衬砌安全性影响系数,开展衬砌背后空洞和厚度不足组合缺陷影响下的衬砌受力特征分析。研究结果表明:衬砌厚度不足和背后空洞的存在会改变衬砌局部刚度及其与围岩的接触状态,从而引起衬砌内力重分布。衬砌缺陷的影响主要集中在缺陷处及其邻近部位,缺陷程度越大,衬砌受影响范围越大;缺陷影响范围内的衬砌轴力减小、弯矩增大,安全系数降低,恶化了结构受力状态。当拱顶存在组合缺陷时,衬砌安全性影响系数随着缺陷程度的增加基本呈线性增长,而当单侧或双侧拱腰存在组合缺陷时呈双线性增长规律。比较而言,背后空洞对结构安全性的影响更大;拱腰组合缺陷的影响大于拱顶部位,较小的组合缺陷就会对结构安全性造成较大影响。

Based on surrounding rock pressure amendment approach,a load-structure model for two-lanehighway mountain tunnel in Yunnan Province was established.By introducing the safety influence coefficient of the lining,the stress characteristics of the lining under the influence of the combined defects which include voids and insufficient thickness at the back of the lining are analyzed.Modelling results showed that the combined defects would change the local stiffness of lining and its contact with the surrounding rock,and thus led to the internal force redistribution of the lining.The influence of lining defects mainly affected the deteriorated zones and their adjacent regions,and the greater the degree of the defect is,the larger the affected area of the lining is.In these deteriorated zones,the internal axial force of the lining dropped dramatically and the bending moment rose up in accordance,which lowered down the safety factor and further worsen the stress state of the whole lining structure.In addition,if the combined defects existed in the tunnel crown,the safety influence coefficient of the lining(deterioration ratio)increased linearly with the increasing of the defect level.While,this ratio showed a bilinear growth law if the combined defects existed in one or two sides of the haunch.Furthermore,comparatively speaking,the influence of void on structural safety is greater than that of insufficient lining thickness.It was worthy note that,the influence of the combined defects at the haunch is greater than those that at the crown;and most importantly,smaller combined defects would impose a significant impacts on the structural safety of tunnel.