衬砌背后空洞影响下隧道结构裂损规律试验研究

衬砌背后空洞的存在严重影响了围岩与衬砌之间的相互作用,极易引起衬砌结构破损并直接影响到运营安全。通过模型试验,系统研究了拱顶与拱肩背后存在双空洞条件下隧道结构裂损演化过程及衬砌结构轴力和弯矩的变化规律。模型试验结果表明:(1)衬砌背后双空洞的存在,严重影响隧道结构的受力状态,易导致衬砌结构承载力不足;(2)拱顶与右拱肩背后存在双空洞条件下衬砌裂缝出现的顺序为:仰拱内表面裂缝→空洞间衬砌内表面裂缝→拱肩空洞右侧衬砌外表面裂缝→拱顶空洞左侧衬砌内表面裂缝→左拱脚衬砌外表面裂缝→右拱腰衬砌外表面裂缝;(3)空洞尺寸变化显著改变了衬砌内力分布,空洞尺寸的增加,引起两空洞间衬砌结构轴力减小而弯矩增大,使两空洞间的衬砌结构破坏程度更严重;(4)衬砌背后空洞的位置及数量对隧道结构裂损过程有较大影响,衬砌背后存在双空洞时衬砌裂缝的传播过程更复杂。研究成果可为衬砌背后多空洞影响下衬砌裂缝病害的防治和修复提供参考。

Experimental studies on effect of voids behind tunnel linings on progressive failure process of tunnel structures

The voids behind the tunnel linings seriously affect the interaction between the linings and the surrounding soils, generally in the form of cracking, spalling or even failure, directly affecting the safety of tunnel operation. The experimental investigation is conducted to examine the effect of the twin voids between the surrounding soils and the tunnel linings at the crown and spandrel on the progressive failure process of tunnel linings, the thrust forces and the bending moments in the tunnel linings. The results show that: (1) The stress state of tunnel linings is greatly affected by the presence of twin voids, which can induce the shortage of load carrying capacity of tunnel structures. (2) As the loading increases, the cracks are noted to propagate firstly at the inner fiber of the tunnel invert, secondly at the inner fiber of the linings between the twin voids, thirdly at the outer fiber of the lining on the right side of the void located at the spandrel diagonally above the tunnel, fourth at the inner fiber of the linings at the left side of the void at the crown, then at the outer fiber of the lining at the left arch spring, finally at the outer fiber of the linings at the right haunch. (3) The changes in void sizes significantly affect the distribution of internal force of the linings. The increase in void sizes results in a decrease in the magnitude of thrust forces in the linings between the twin voids, while the magnitude of bending moments between the twin voids increases as the void sizes increase, which then causes significant damage to the tunnel linings between the twin voids. (4) The failure process of tunnel linings is greatly affected by the location and quantity of voids. The propagation laws of lining cracks are even more complicated under the influence of twin voids. These studies can provide reference for preventing and repairing lining cracks influenced by the multiple voids behind the tunnel linings.