富水大断面公路隧道水压模型试验及衬砌结构力学行为研究

Hydraulic Model Test and Mechanical Behavior of Lining Structure in the Water-filled Large Cross-section Highway Tunnel

为研究隧道衬砌在围岩压力及外水压力综合作用下的受力特征、结构安全性及破坏过程,采用自制的均匀水压模拟加载装置及隧道地层复合试验台架,实现对围岩压力及外水压力的分别控制加载,完成在深埋条件下不同外水压力作用下衬砌结构受力模型试验。运用ANSYS有限元软件分阶段计算衬砌在水土压力作用下的受力特征,计算各部分安全系数,并与试验结果对比分析。研究表明:采用抽真空的方法模拟外水压力时,外水压力值越大,试验结果越接近真实情况,当外水压力达到150 kPa时,其差值可控制在5%以内;在外水压力及围岩压力的作用下,墙脚及拱底分别受最大正弯矩及最大负弯矩作用,且安全系数较其他位置小;随着外水压力的增大,衬砌所受的轴力及弯矩持续增大,且增大速率基本呈线性,其中墙脚位置增长速率最快;随着荷载的增大衬砌结构墙脚最先发生破坏,墙脚裂缝发展导致衬砌结构应力重分布,最终引起拱底开裂;墙脚的裂缝导致墙脚处承受的正弯矩不断减小,拱底承受的负弯矩不断增大,安全系数不断减小;当墙脚的裂缝宽度发展至1.5~2.0 mm时,试验数据及数值模拟结果计算所得拱底安全系数降低至1.5左右,拱底不再满足承载要求,与试验中衬砌的开裂行为相吻合。所提出的模型试验方案可为类似模型试验提供参考,研究成果可为富水大断面公路隧道的设计及安全评估提供依据。

In order to study the stress characteristics,structural safety and failure modes of the tunnel lining under the effects of surrounding rock pressure and external water pressure,a self-made homogeneous hydraulic pressure simulation device and a tunnel stratum composite test bench were used to simulate the loaded of different external water pressures under deep burial.Studies show that when using vacuum to simulate the external water pressure method,the greater the external water pressure value,the smaller the test error.When the external water pressure reaches 150 kPa,the error can be controlled within 5%;in the case of fixed depth As the external water pressure increases,the axial force and bending moment of the lining increase continuously,and the increase rate is basically linear;as the load increases,the toe of the lining structure first breaks,and the continuously cracking of the toe of the lining,resulting in redistributing of the structural stress,eventually cracks in the inverted arch;cracks in the walls cause the permanent bending moment at the foot of the wall to continue to decrease,and the negative bending moment of the inverted arch continue to increase,and the safety factor continue to decrease.When the bending moment of the foot of the wall fall to 85%of that before cracking,the safety factor of the invert is reduced to 1.41 and the invert arch crack and destroy.This article involves the model test program can provide a reference for similar numerical model test,the research results can provide a basis for the design and safety assessment of water-rich large section highway tunnel.