Study On Deformation Monitoring Of Frozen Soil Subgrade Based On FBG

With the progress of economic construction and the development of Belt and Road Initiative construction,the security of energy and resources in our country has been guaranteed,the infrastructure has been promoted,and the transportation engineering has also been developed rapidly.The rapid expansion of roads,bridges,tunnels and other infrastructure has greatly promoted the development of society.However,because the frozen soil area accounts for more than half of the land area in our country,although the traffic network has been covered,the safety construction of the traffic engineering has been seriously hindered because of the harsh environment in the frozen soil area.Especially the road subgrade built on the frozen soil area,which is used as a hidden project,whether it is the inspection of physical indexes.Surveying or road safety evaluation has always been a difficult problem to solve,which is seriously related to the safety of transportation.Therefore,in order to measure the deformation of road subgrade in permafrost area,this paper explores the method and feasibility of using FBG sensor to monitor the deformation of frozen soil subgrade by using fiber Bragg grating((FBG))as the means of measuring the deformation of road subgrade in permafrost area.This paper first introduces the commonly used subgrade detection methods at present,the research status of FBG testing technology at home and abroad,and then aiming at the problem of using FBG sensor to measure the deformation of frozen soil subgrade,the main research work is as follows:(1)Based on the principle of FBG sensor and the mechanical mechanism of monitoring beam,the deformation of FBG monitoring beam at soilless room temperature is calibrated and measured.According to the actual measurement value,the deformation calculation conversion coefficient of FBG monitoring beam is given;(2)In order to solve the cross-sensitivity problem of FBG,the negative temperature influence experiment is carried out,the negative temperature influencecoefficient is given,the calculation method of temperature compensation is put forward,the deformation calculation results before and after eliminating the temperature influence are compared,and the deformation characteristics of FBG monitoring beam at negative temperature are discussed;(3)Considering the influence of freeze-thaw cycle,the laboratory experimental subgrade model is established.The deformation measurement experiment of subgrade model under the influence of freeze-thaw cycle and the calculation method of continuation temperature compensation are carried out.The applicability of FBG monitoring beam in seasonal frozen soil deformation measurement and the accuracy of the measurement results are analyzed.