| With the acceleration of the urbanization process in China,the subway shield tunnel has become an important way to solve the urban road congestion with its economic advantages and small influence on the urban ground traffic.Domestic and foreign research shows that with the increase in service time,the tunnel itself will be a variety of different degrees of deformation damage,the need for timely and comprehensive monitoring,diagnosis and maintenance.As the traditional monitoring technology and observation methods can not meet the requirements of modern tunnel deformation monitoring,it is urgent to develop advanced monitoring techniques and methods to meet the shield tunnel structure health monitoring.Distributed optical fiber monitoring technology can break through the limitations of traditional point sensing technology,can realize the long-distance distributed monitoring of metro shield tunnel,obtain the overall deformation of the tunnel,so as to provide scientific basis for tunnel structure health diagnosis and maintenance.In this paper,two kinds of optical fiber monitoring techniques are used to summarize the structure and causes of shield tunneling structure:quasi-distributed fiber Bragg grating(FBG)and Brillouin optical frequency domain analysis(BOFDA),Developed and improved the corresponding optical fiber sensor and sensor cable,designed the corresponding layout program,and through the indoor model test to verify the feasibility and accuracy of the layout program;for fiber monitoring of massive data,developed a corresponding And the distributed fiber monitoring system was established.Based on the monitoring data of the past two years,the health status of the shield tunnel was analyzed and diagnosed.The main work and achievements of the paper are summarized as follows:(1)Analyzed and summarized the common shield tunnel structure diseases,and analyzed the relationship between the causes of the disease and the surrounding environment,and sorted out the monitoring focus of the shield tunnel structure disease.(2)An indoor test was conducted to test the performance of a distributed fiber demodulator.The performance of the Brillouin Scattering Light Frequency Analysis Instrument(BOFDA)and Time Domain Analysis Demodulator(BOTDA)was tested.The test results show that the accuracy,repeatability and dynamic range of BOFDA produced by fibrisTerre are much higher than that of Neubrex's BOTDA,and the accuracy isą2??.Although the spatial resolution is lower than that of BOTDA,the shield tunnel is similar Engineering structural health monitoring requirements.(3)Improved FBG-based static level,surface strain gauges and displacement gauges for shield tunneling diseases,and carried out a series of test calibration tests;improved the existing metal cable-like strain and polyurethane strain sensor Fiber optic cable,making it more in line with the shield tunnel structure health monitoring requirements(4)The simulation test of the Zhang-joint deformation monitoring of the shield tunnel is carried out,and the deformation law of the closure and opening stage of the corresponding section is obtained.It is proved that the tight polyurethane sensor cable has a good back Elasticity,can be opened and closed at the same time to monitor the closure of the joint;in the case of shield tunnel is relatively closed,you can use this strength is not good but good resilience of the sensor cable.(5)The deformation test of the shield tunnel is carried out,and the relationship between the deformation of the shield block and the fiber strain is deduced theoretically.The sensitivity of the optical fiber measurement is related to the fixed point spacing.The deformation error of the measured value of the optical fiber can be controlled within 10%,which can meet the monitoring requirements of the tunnel deformation.(6)A similar physical model test of tunnel convergence deformation is carried out to verify the convergence of the tunnels.It can be used to verify the convergence of the tunnels.The simplified convergence model is used to optimize the tunnel convergence The relationship between the strain data and the convergence value is established,and the calculation model is tested by model test.(7)The shield tunnel deformation optic fiber monitoring system is developed.The system is composed of FBG monitoring subsystem and distributed strain monitoring subsystem.Aiming at the massive data obtained by distributed fiber monitoring,the corresponding data processing software is designed and realized,which can realize data interception,reverse and poor.Based on wavelet analysis And polynomial fitting,etc.The method of data smoothing denoising is designed.The visual tunnel model is developed to visualize the three-dimensional distribution of tunnel deformation.(8)Taking the monitoring area of three shield tunnels in Suzhou rail transit as an example,this paper applies the results of the paper to the actual monitoring of shield tunnel deformation,and successfully established the optical fiber monitoring system of Suzhou Rail Transit Tunnel,and obtained Suzhou Subway tunnel monitoring section of the last two years of deformation information.The results show that the deformation of the shield tunnel is mainly concentrated at the joint of the segment,and the deformation of the segment itself is much smaller than that of the joint in the construction of the shield tunnel.The monitoring data strain anomaly point,can correspond to the site of the leakage point,proved the effectiveness and accuracy of the monitoring system;in the operation of the tunnel is relatively closed interval,the temperature changes with the external environment temperature trends,And the variation range of the temperature is smaller than that of the ambient temperature.The deformation law of the seams of the shield tunnel is consistent with the change of the ambient temperature in the tunnel,which indicates that the deformation at the joint is mainly caused by the thermal expansion and contraction of the pipe The expansion of the expansion joints on the bed,the maximum compression of 1 mm,the maximum amount of 1mm,are much smaller than its reserve,deformation within the normal range. |
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