BOFDA-based Monitoring And Stability Evaluation Of The Shield Tunnel

With the construction of urban rail transit in China,shield tunnel construction has been booming.At the same time,the stability of the subway shield tunnel during the construction period and the operation period becomes the focal point of the modern tunnel project builder.Therefore,it is important to explore an effective monitoring method.On the basis of consulting a large number of relevant literatures at home and abroad,the author has developed a distributed optical fiber sensor suitable for shield tunnel engineering monitoring based on the Suzhou tunnel traffic shield tunnel structure health monitoring project.The BOFDA sensing principle is introduced.A lot of indoor experiments have been done to verify the accuracy and stability of BOFDA.This paper expatiates the application of large-scale finite element analysis software ABAQUS in tunnel stability analysis and combines it with BOFDA monitoring to provide the tunnel stability evaluation method.The performance of the distributed sensing cable is verified by the indoor physical model test.The method of calculating the convergence of the tunnel based on the distributed sensing cable data is presented.The concrete contents are as follows:(1)This paper discusses the research status of shield tunnel structure monitoring and stability analysis,and introduces the distributed fiber sensing technology and its application in shield tunnel monitoring.The basic profile of the Suzhou Metro shield tunnel and the engineering geological conditions of the location of the shield tunnel are described.The main factors that affect the safety of tunnel construction and operation are listed in detail,and the main contents of tunnel monitoring and evaluation are listed.(2)The sensing principle of Brillouin optical frequency domain analysis(BOFDA)is described.The spatial resolution and testing accuracy of BOFDA were verified by laboratory test,and the technical parameters and performance of BOFDA and BOTDA were compared and analyzed.(3)This paper introduces the large-scale finite element analysis software ABAQUS and its application in the tunnel stability analysis,and establishes the two-dimensional plane strain model based on the tunnel excavation of Suzhou subway shield tunnel.This will lay the foundation for analyzing and validating BOFDA monitoring results.(4)The physical model test of the convergence of shield tunnel is carried out.The whole process of the test scheme,the test process and the test results of the tunnel physical model test are introduced in a complete way.The calculation model of tunnel convergence deformation is put forward,and the convergence of tunnel is analyzed based on the monitoring data,and the effectiveness of distributed fiber sensing technology in tunnel structure monitoring is demonstrated.The calculation model is reasonable and the reasonable calculation method is provided for the tunnel convergence deformation monitoring.(5)This paper introduces the method of distributed cable sensing technology in the deformation monitoring of shield tunnel structure in detail,and puts forward the method of cable laying applied to the deformation monitoring of tunnel structure,taking the construction of Suzhou subway shield tunnel construction and operation period as an example.The corresponding monitoring results are analyzed and the tunnel stability evaluation is made.