考虑二次衬砌有效承载厚度的隧道结构安全系数解析模型

Analytical Model of Tunnel Structure Safety Factor Considering Effective Bearing Thickness of Secondary Lining

为研究严重腐蚀环境和施工缺陷等导致的衬砌厚度损失对隧道结构安全的影响,基于弹性地基曲梁理论和空间状态法建立二维衬砌受力解析解模型,采用Laplace变换求解衬砌各位置处的内力与位移,并与同工况下的数值模拟结果进行对比验证。数值模型中,通过折减局部二次衬砌厚度以及调整折减范围,模拟二次衬砌有效承载厚度的损失情况。研究结果表明:1)增大二次衬砌厚度损失的范围和程度,均会导致厚度损失处截面弯矩显著降低,但轴力变化较小。2)二次衬砌厚度损失对安全系数的影响主要集中在厚度损失附近区域。随着损失范围的增加,厚度损失区域内的弯矩呈现下凹式抛物线形降低,安全系数经历突降—回升—稳定3个阶段。3)当损失厚度较小时,安全系数受到轴力偏心变化的影响较小,与有效承载厚度近似呈线性关系。值得注意的是,劣化厚度继续增大后,轴力偏心距降低对安全系数的增益迅速提升,当其大于承载截面积的劣化效益时,计算安全系数反增,但存在局部结构变形破坏的风险。

To investigate the effect of effective lining bearing thickness loss induced by severe corrosive environment and construction defects on the tunnel structural safety,a two-dimensional lining force analytical solution model is established based on elastic foundation curved beam theory and spatial state method.The Laplace numerical transformation is used to solve the internal force and displacement at each position of the lining,and the results are compared with that of the numerical model under the same working conditions.The effective secondary lining thickness loss is simulated by discounting the local secondary lining thickness and adjusting the discount range.The results reveal the following:(1)Increasing the range and degree of secondary lining thickness loss leads to a significant reduction in the cross-sectional bending moment at the thickness loss.However,the change in axial force is small.(2)The influence of secondary lining thickness loss on the safety coefficient is mainly concentrated in the area near the thickness loss.As the loss range increases,the bending moment in the thickness loss area shows a concave parabolic decrease,and the safety coefficient experiences sudden drop,rebound,and stability.(3)When the loss thickness is small,the safety coefficient is less affected by the change in axial eccentricity,and the effective bearing thickness is approximately linear.After the deterioration thickness continues to increase,the gain in safety coefficient by reducing axial eccentricity increases rapidly,and when it is greater than the deterioration benefit of the bearing cross-sectional area,the calculated safety coefficient increases.However,there is a risk of local structural deformation damage.