摘要
富水地层公路隧道衬砌背后空洞的存在恶化了其结构的受力状态,使衬砌易于开裂进而影响隧道的营运安全。研制外水压加载装置,该装置在二衬模型内部创造一个封闭的负压环境,通过控制模型内外气压差来实现外水压的等效加载,同时结合隧道–地层复合模拟试验系统开展几何相似比为1∶30的室内模型加载试验,全面研究不同位置空洞与不同外水压荷载共同作用下二次衬砌的受力分布规律及开裂特征。结果表明,衬砌背后存在空洞时的二衬的轴力与弯矩总体不再呈对称分布,不同位置空洞对衬砌结构的受力影响不同,空洞附近区域的衬砌内力变化最为显著;无论空洞位于何位置,随着外水压力的增大,二衬轴力及弯矩均大致呈线性增大趋势,空洞附近区域的轴力及弯矩增大速度明显大于二衬其他部位;偏心距则随外水压的增大而减小,水压超过150 kPa后基本不发生变化;相同外水压下,加宽带二衬轴力与弯矩明显大于三车道,分布及变化规律则大致相同;应力场为竖直主应力场时,外水压下左边墙空洞对于衬砌结构的承载力影响最大,拱顶空洞次之,仰拱空洞最小;背后存在空洞的衬砌部位的裂缝数量及开裂程度明显大于其他部位。
The existence of voids behind highway tunnels in water-rich strata deteriorates the stress state of the lining structure,make it vulnerable to cracking and affects its integrity during service. A device for external loading test was therefore developed with a controllable air pressure between the primary and secondary linings. The voids can be simulated by regulating the pressure difference,equivalent water pressure in the voids. Using this device together with a tunnel-ground simulation facility,a model test with a geometric similarity ratio of 1：30 was conducted. The force distribution and cracking features on the secondary lining with respect to different external water pressures and void distribution were analyzed. The axial force and bending moment distribution on the secondary lining were found no longer be symmetrical due to the voids. The voids at different location impacted differently to the mechanical behavior of lining,especially at locations near the voids. In the area close to the voids,the axial force and bending moment increased at a rate significantly higher than in other parts of lining. As the external water pressure increased,a nearly linear increasing trend of axial force and bending moment was observed irrespective of the void locations. The eccentricity decreased as the water pressure rose,and it tended to remain constant once the water pressure reached 150 k Pa. Given the same pressure level,the axial force and the bending moment in tunnels with widening band were significantly greater than that in three-lane tunnels,though the distribution was similar. In the cases where the vertical stress field dominated,the voids behind the left wall had the most significant effect on the bearing capacity of lining,followed by voids behind the crown and invert. Both the number and severity of cracks on the lining with voids presented nearby exceeded the other parts noticeably.
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2016年第8期1648-1658,共11页
Chinese Journal of Rock Mechanics and Engineering
基金
国家自然科学基金资助项目(51278422
51578460)
四川省青年科技基金(2012JQ0021)~~
关键词
隧道工程
衬砌背后空洞
外水压
二次衬砌
内力特性
开裂
模型试验
tunneling engineering
voids behind the lining
external water pressure
secondary lining
mechanical behavior
crack feature
model test
