Shen Sheng, Lv Huaxin, Ma Sheng-Lan
College of Civil Engineering, Fuzhou University, Fuzhou 350108, China.
Zhongtian Construction Group Zhejiang Steel Structure Co., Ltd., Hangzhou 310008, China.
Sensors (Basel). 2019 Apr 18;19(8):1840. doi: 10.3390/s19081840.
It is difficult to detect and evaluate the structural damage in a shield tunnel during operation because many traditional techniques based on the observation of vibrations are limited in daily monitoring in tunnels. Thus, the curvature radius of a static longitudinal settlement curve is used to identify the residual health and safety of an in-service shield tunnel. However, there are still two problems. The curvature radius is suitable for a qualitative judgment rather than a quantitative evaluation for longitudinal damage detection. Moreover, the curvature radius, which is calculated from the measured settlements of three neighboring points, gives an average damage degree in a wide scope only and is difficult to use to identify the damage's precise location. By means of the analysis of three kinds of longitudinal failure modes in a shield tunnel, this paper proposes: (1) a damage detection method based on the monitored increment of the neutral axis depth; and (2) an index to evaluate longitudinal damage. The index is composed of the residual ratios of the equivalent flexural stiffness (HFM1) and the equivalent shear stiffness (HFM3). The neutral axis position and the proposed damage index can be determined using long-gauge Fiber Bragg Grating sensors. Results from numerical simulations show that the deviation between the HFM1 and the true value residual ratio of the equivalent flexural stiffness is no more than 1.7%. The HFM3 is equal to its true value in the entire damage process. A loading experiment for a scaled-down model of a shield tunnel using long-gauge Fiber Bragg Grating sensors indicated that the errors in the HFM1 were no more than 5.0% in the case of early damage development (HFM1 ≥ 0.5). The maximum error did not exceed 9.0% even under severe damage conditions in the model. Meanwhile, the HFM3 also coincided with its true value in the entire testing process.
在盾构隧道运营期间，很难检测和评估其结构损伤，因为许多基于振动观测的传统技术在隧道日常监测中存在局限性。因此，利用静态纵向沉降曲线的曲率半径来识别在役盾构隧道的剩余健康和安全状况。然而，仍然存在两个问题。曲率半径适用于定性判断，而不适用于纵向损伤检测的定量评估。此外，由相邻三个点的测量沉降计算得到的曲率半径仅给出了较大范围内的平均损伤程度，难以用于确定损伤的精确位置。通过对盾构隧道三种纵向破坏模式的分析，本文提出：（1）一种基于中性轴深度监测增量的损伤检测方法；（2）一个评估纵向损伤的指标。该指标由等效抗弯刚度（HFM1）和等效抗剪刚度（HFM3）的剩余比率组成。中性轴位置和所提出的损伤指标可使用长标距光纤布拉格光栅传感器来确定。数值模拟结果表明，HFM1与等效抗弯刚度真实值剩余比率之间的偏差不超过1.7%。HFM3在整个损伤过程中与真实值相等。使用长标距光纤布拉格光栅传感器对盾构隧道缩尺模型进行的加载试验表明，在早期损伤发展阶段（HFM1≥0.5），HFM1的误差不超过5.0%。即使在模型的严重损伤条件下，最大误差也未超过9.0%。同时，HFM3在整个测试过程中也与真实值相符。
