大断面深埋高水压盾构隧道实测内力反算与分析

Reverse Calculation and Analysis of Measured Internal Force of Deeply Buried Shield Tunnels with Large Crosssection Under High Water Pressure Conditions

摘要:

结合南京地铁3号线大直径盾构隧道工程，对隧道管片钢筋应变进行了现场测试，基于既有的管片内力反算方法，考虑混凝土非线性性质及管片接头，提出了适用于深埋高水压盾构隧道的内力改进算法，并对改进算法反算内力与结构设计计算内力进行了对比分析.结果表明：改进算法更能反映管片的实际受力状态，更适用于荷载模式复杂且接头传力机制多变的大断面深埋高水压盾构隧道；采用设计方法计算的深埋高水压盾构隧道管片及接头内力与改进算法反算内力的分布规律基本一致，但在量值上具有一定的差异；采用设计方法计算的管片及接头轴力为改进算法反算轴力的1/2左右，反算的管片弯矩在拱底位置与惯用法计算弯矩接近，在拱腰及拱顶位置与梁弹簧法更为接近，反算的接头弯矩大于梁弹簧模型计算接头弯矩.研究成果可为大直径深埋盾构隧道设计提供参考.

关键词:盾构隧道; 现场监测; 实测应变; 管片内力反算

Abstract:

A field monitoring program was performed to measure the steel strain in segments of a shield tunnel deeply buried with high pore water pressure of Nanjing Metro Line 3 project. Concerning the nonlinear properties of concrete and segment joint of tunnel, an improved algorithm was proposed to compute the internal forces of deeply buried shield tunnels under high water pressures based on three existing reverse calculation methods, and the results were compared to the ones computed in structural design. The results show that the improved algorithm can reflect the actual stress state of segments, especially the lining of shield tunnels deeply buried with high pore pressure; the distribution of internal forces calculated in design is almost equal to the one computed by the improved algorithm, but there are some quantitative discrepancies; the axial forces of segments and joints calculated in structural design are approximately half of the backcalculation results; the bending moments of segments calculated by the proposed algorithm are close to the results of the modified routine method at the bottom of the tunnel while approximate the results of the beamspring model at the roof and haunch of the tunnel, and the bending moments of segment joints are greater than the results of the beamspring model. The insights provided from this study can contribute to the improvement of largesection shield lining design.

Key words:shield tunnel; field monitoring; measured steel strain; reverse calculation of internal force in segments