空洞缺陷影响下衬砌结构受力特征分析

Analysis of stress characteristics of lining structures under the influence of cavity defects

针对隧道在空洞缺陷下会对衬砌结构造成危害的问题,提出了一种基于等腰梯形应力面积等效方法对荷载结构模型进行围岩压力修正,对拱顶背后不同空洞大小下衬砌结构的受力特征和安全性进行了研究。结果表明:空洞缺陷会使空洞两侧出现应力集中和应力重分布现象,进行围岩压力修正的荷载结构模型相较于未修正荷载结构模型能有效的考虑到这些不利因素,更切合工程实际。不同空洞大小会导致衬砌结构承载能力发生改变,衬砌结构受力特征变得复杂,隧道结构整体安全性降低。修正荷载结构模型下,拱顶背后空洞从20°增大到60°时,拱顶位置处轴力减小了48.3%;弯矩值增长了3.2倍,弯矩形态严重“外凸”;安全系数降低了81.3%。

To address the problem that tunnels can cause hazards to the lining structure under cavity defects,an isosceles trapezoidal stress-area equivalent method based on the isosceles trapezoidal stress-area equivalent method for the load structure model with envelope pressure correction is proposed to study the force characteristics and safety of the lining structure under different cavity sizes behind the vault.The results show that the empty cave defects will cause stress concentration and stress heavy distribution on both sides of the empty cave. The load structure model that performs the correction of surrounding rock pressure correction can effectively consider these unfavorable factors compared to the unsatisfactory load structure model,and it is more actual in the project. Different empty holes will cause the bearing capacity of the lining structure to change,the characteristics of the lining structure have become complicated,and the overall safety of the tunnel structure is reduced. Under the modified load structure model,when the cavity behind the vault increases from 20° to 60°,the axial force at the vault position decreases by 48.3%;the bending moment value increases by 3.2 times,and the bending moment pattern is severely "convex";the safety factor decreases by 81.3%.