The Preliminary Study On DFOS-based Land Subsidence Monitoring And Its User's Code

With the acceleration of urbanization and the over-use of groundwater resource,land subsidence hazard has become increasingly worse,seriously restricts the sustainable development of the city,therefore,The monitoring of land subsidence has become an important part of the work of disaster prevention and mitigation.Distributed Optical Fiber Sensing Technology(DFOS)as a new kind of monitoring technology,has been continuously applied and promoted in the land subsidence monitoring in recent years,it is necessary to formulate the corresponding technical code in order to standardize the application of this technology in the land subsidence monitoring.In this paper,on the basis of summarizing the domestic and foreign relevant achievements,systematic summarize the principle,method,scope of application,the types and performance of optical cable,construction and installation,data processing and analysis of the DFOS technology on land subsidence,combined with the research of DFOS technology on land subsidence monitoring of my research group in recent years,finally,preliminarily formed the technology code of DFOS technology on land subsidence monitoring.The main achievements of this paper as follows:(1)The advantages and disadvantages of the technology commonly used on land subsidence monitoring are analyzed,and the current situation of DFOS technology on land subsidence monitoring at home and abroad are discussed,expounded the importance of formulating the technical code of DFOS technology on land subsidence monitoring.(2)The principle,characteristics and applicable scope of three technology including BOTDR,BOTDA,FBG in DFOS technology on land subsidence monitoring are detailed introduced,the deformation characteristics of the ground subsidence and ground fissures are analyzed,summarized the difficulty of monitoring including vertical and horizontal deformation monitoring in soil,large deformation monitoring,construction and installation of optical cable and temperature compensation.(3)The key technology including demodulation instruments,sensors and optical cable,the optical cable of temperature compensation,and construction and installation of sensors of DFOS technology on land subsidence monitoring are detailed introduced.(4)The system of DFOS technology on land subsidence monitoring,and presented performance evaluation standard of optical cable was studied and built.(5)The optical fiber monitoring method of vertical buried type was adopted,to monitor the field of land subsidence in ShengZe,verified the effectiveness of this method.The results show that the technology of BOTDR and FBG,can accurately position the sand layer and the tendency of deformation of soil.(6)The optical fiber monitoring method of horizontal direction buried type and horizontal direction fixed-point type was adopted,to monitor the field of ground fissures in YangShuLi.The results show that wire rope and fixed-point distributed sensing optical cable not only have very good protection effect to the fiber core inside the optical fiber,and couple with the soil;The method of horizontal direction fixed-point can effectively locate the position of the ground fissure occurrence and trend of soil deformation.(7)On the basis of the above research,preliminarily formed the technology code of DFOS technology on land subsidence monitoring.