Research On Intelligent Health Monitoring And Evaluation System Of Jinan Yellow River Tunnel During Operation Period

In recent years,due to the advantages of fast tunneling,high safety,and less impact on the surrounding environment of the city,the shield method has been adopted in many subway construction projects.However,with the increase of the operating life of the tunnel,due to the influence of various reasons such as water seepage pressure,earth pressure,convergence extrusion,and tunnel operating pressure,a series of tunnel diseases will occur,such as segment cracks and joint openings.thereby endangering driving safety.In order to ensure the safety of large-diameter shield tunnels during the operation period,it is necessary to establish a special tunnel structure health monitoring system to carry out intelligent health monitoring and structural safety evaluation during the operation period of shield tunnels to avoid the occurrence of tunnel diseases.Based on the large-diameter shield tunnel of the Yellow River in Jinan,this paper comprehensively uses the research methods of literature research,numerical simulation and theoretical analysis for the health monitoring and safety assessment of the main body of the structure in the second half of the west line of the tunnel.The research results obtained in the paper are as follows :(1)Taking the second half of the west line of Jinan Yellow River Tunnel as the monitoring object,based on its soil layer and surrounding environment,the ANSYS modeling software is used to simulate the influence of stratum,geology,water pressure and other factors on the safety of the tunnel structure.The conclusion of the finite element analysis shows that the load-bearing section on the surface,the high-covering soil section of the tunnel and the deepest section of the main channel where the tunnel is located should be the priority areas when selecting the monitoring section.The arch bottom and two waists of the tunnel should be the parts that need to be monitored.(2)Through the analysis of common diseases of shield tunnels,combined with the field investigation of Jinan Yellow River Tunnel,the thesis determines that the main contents to be monitored are the external load of the tunnel(water and earth pressure),the axial force of the bolts of the segments,and the opening of the joints between the segments and the strain of segment concrete;According to the key monitoring items sorted out,a fiber grating earth pressure gauge,a fiber grating displacement gauge,and a fiber grating bolt axial force meter were developed to monitor the water and soil pressure outside the tunnel,the axial force of the joint bolt,and the joint opening amount respectively,and the distributed optical fiber is used to monitor the concrete strain of the segment.(3)Based on the second half of the west line of the Jinan Yellow River Tunnel,a large-diameter shield tunnel structural health monitoring system was established.A comprehensive analysis of the data collected in recent months led to the following conclusions:The tunnel structure is significantly affected by changes in the external water level,temperature,and stratum.The load on the tunnel vault is greatly affected by the water level change.The two waists are less affected by the water level than the vault due to the poor permeability of the stratum.The strain of the segment concrete is obviously affected by the external load.Under the influence of the upper load,there will be a positive bending moment on the tunnel vault,which will cause the segment concrete to be stretched;The axial force of the circumferential bolt is greatly affected by the water level,and the axial force of the longitudinal bolt is greatly affected by the temperature,and decreases with the increase of temperature.The opening amount of the segment joint is similar to the variation law of the axial force of the segment bolt.(4)A safety evaluation model of Jinan Yellow River Tunnel based on fuzzy comprehensive evaluation method is established.The health status of the tunnel structure is divided into four levels,and the different warning intervals of the tunnel parameters and the membership functions under different warning levels are obtained;A multi-level organization evaluation factor set that affects the safety of tunnel structure is established,and the corresponding weight set is determined by using AHP;By constructing a series of operation models,the structural safety assessment and early warning of the whole second half of the west line of the Jinan Yellow River Tunnel,each monitoring section and different monitoring parts are realized.