Distributed Optical Fiber Monitoring Technology On Deformation Of Land Subsidence

Land subsidence has the character of slowness, accumulation and be difficult to recover effectively. A total of79000Km2areas of China exists land subsidence exceeding200mm, and it is showing a tendency to be worse. The land subsidence monitoring is crucial to prevent land subsidence and control the harm of it. In this thesis, distributed optical fiber sensing technology is applied to monitor he deformation of land subsidence. A series of monitoring methods are designed, the technical difficulty has been analyzed, and indoor test simulation experiments and field work are also carried out. And then the following results are achieved:1. Four distributed optical fiber sensing monitoring methods were designed, the monitoring method with fixed point in horizontal direction, the monitoring method with direct burying in horizontal direction, the displacement monitoring method with deformation meter and the monitoring method with direct burying in vertical direction, based on BOTDR tech, to monitor the land subsidence and deformation of the ground fissure distributedly.2. A systematic study of monitoring principle, technical difficulties and implementation for the four methods referred above were done. As a result, methodology of implementation has been improved and tends to be stability.3. Performance test and simulation trial were carried out to determine the monitoring accuracy and the scope of application of the methods. Feasible, scientific and effective methodology of implementation was formed.4. Four methods were applied in typical area with land subsidence and deformation of ground fissure to monitor. It is verified by practice that the methodology of implementation is feasible, scientific and effective. Analysis of monitoring data showing that the monitoring method with fixed point in horizontal direction and the monitoring method with direct burying in vertical direction are able to detect the deformation information of soil mass with high precision. It has been demonstrated that the monitoring method with direct burying in horizontal direction and the displacement monitoring method with deformation meter are not applicable to monitoring of deformation of ground fissure.5. According to the vertical buried monitoring data, soil deformation in the observation area of land subsidence within measured depth was analyzed in detail to master the deformation law of the land subsidence.