Experimental study on buried pipeline instrumented with fiber optic sensors under ground collapse
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摘要: 目前,由于地层塌陷引起的埋地管道突发性事故时有发生,然而国内外关于这方面的研究相对滞后,尚无相关理论预测地面沉陷过程中管道及周边土体的受力变形规律。通过基于光纤布拉格光栅（FBG）的模型试验,研究了地层塌陷时管道的受力特征及土层的沉降分布规律,并推导提出了由光纤应变测值计算管道弯矩的方法。试验结果表明：①随着塌陷体积的增加,埋地管道呈现出顶底逐渐受压和侧边受拉的应变状态；②根据埋设在土体中的FBG应变读数可以将土体变形发展分为应力重分布阶段、土体蠕变压缩阶段和塌陷后的稳定阶段3个阶段；③地面沉降符合修正高斯分布曲线,在此基础上建立了光纤水平向应变与地面沉降变形之间的数学模型,并对比分析了理论计算值与试验值,发现二者具有良好的一致性。该研究为埋地管道安全性评估和灾变预警提供了一种新的思路和方法。
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关键词:
- 光纤布拉格光栅（FBG） /
- 埋地管道 /
- 光纤传感技术 /
- 地层塌陷 /
- 地面沉降
Abstract: In recent years, the pipeline accidents caused by ground collapse are frequently reported. However, the relevant studies are still lagging behind, and there are few theories to predict the deformation and mechanical characteristics of buried pipelines and surrounding soils in the process of ground settlement and collapse. In this study, the stress state of the pipeline and soil settlements during ground collapse are investigated through fiber Bragg grating (FBG)-based model tests, and the method for calculating the bending moment of the pipeline using fiber-optic strain measurements is derived. The test results show that: (1) The compressive strains accumulate on the pipeline top and bottom with the increase of collapse volume, and both the pipeline sidewalls are in the strain state of tension. (2) According to the FBG strain monitoring results, the development of soil deformation can be divided into three stages, i.e., the stress redistribution stage, the creep compression stage and the stability stage after collapse. (3) The ground settlement pattern fits well with the modified Gaussian distribution. On this basis, the mathematical model between the horizontal strain measured by the fiber optic sensors and the ground settlement is established. At the same time, the results of theoretical calculation and experimental data are compared, and they appear to agree well with each other. This work provides a new approach to effectively evaluate the safety and implement hazard warning of buried pipelines.-
Keywords:
- fiber Bragg grating /
- buried pipeline /
- fiber optic sensing /
- stratum collapse /
- ground settlement
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图 2 Geo-PIV计算得到的土体位移场云图
Figure 2. Contours of soil displacements calculated by Geo-PIV
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图 6 地层塌陷前后埋地管道形状对比图
Figure 6. Comparison of buried pipeline shapes before and after ground collapse
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图 8 不同阶段地表沉降拟合值与实测值的对比结果
Figure 8. Comparison of fitted and measured ground surface settlements in different stages
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图 9 地表最大沉降拟合值与实测值的对比结果
Figure 9. Comparison of fitted and measured maximum ground surface settlements
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图 10 埋地光纤变形受力示意图
Figure 10. Diagram of deformation and stress of buried optical fibers
表 1 修正高斯曲线公式的拟合参数及地表沉降最大值
Table 1 Fitting parameters of modified Gaussian curve and maximum ground surface settlements
试验阶段 n i/mm Smax/mm 实测 拟合 Ⅰ 1.3 131.1 0.70 6.0 5.6 Ⅱ 2.3 160.5 1.20 10.2 10.1 Ⅲ 2.4 172.0 1.22 17.5 16.2 
下载: 导出CSV
表 2 由高斯模型计算的参数值
Table 2 Calculated parameters of Gaussian model
试验阶段 Smax/mm i/mm Ⅰ 5.51 25.6 Ⅱ 9.45 26.7 Ⅲ 17.24 30.4
下载: 导出CSV
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