A calibration test on optical fiber sensing device for karst collapse monitoring
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摘要: 根据岩溶土洞(塌陷)变形演化特点,分析土体与传感光纤之间的力学关系,简化塌陷力学模型,加工塌陷模拟试验装置并进行试验。首先通过对光纤加载和卸载来模拟土洞形成过程顶板荷载的变化及分析传感光纤相应的变形和轴向应变特点,然后研究了土洞规模变化对光纤传感监测的影响。研究表明:在土洞形成过程中,因土洞规模和上覆土层荷载不一而导致的应力场的分布变化,以及不同光缆对应力场变化响应灵敏性的差异,是影响分布式光纤传感技术在岩溶土洞中应用的关键因子。文中所标定的光纤传感试验装置能较好地显示岩溶土洞形成演化过程中的应变变化特征,说明分布式光纤传感技术可应用于岩溶土洞的监测预警。Abstract: In line with the deformation characteristics of the sinkhole collapse, the mechanic relation between the soil body and the sensing fiber is analyzed, the mechanic model of collapse is simplified, and simulation test device is processed and tested. Firstly, the sinkhole formation process is stimulated with the orderly changes under load on the optical fiber. And then, the impact of the changes in sinkhole size on the sensing fiber monitoring is analyzed. The study shows that the key factors affecting the application of the technology include the stress field distribution changes led by overlying loads and hole size change during the formation of the holes, and the difference of responding sensitivity to the stress field change among different optical cables. The calibrated optical fiber sensing device in the study can preferably show the features of the stress field changes during the formation and evolution of the hole, which states that the optical fiber sensing device can be used in monitoring and early warning for karst collapse.
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