Study On Mechanical Properties Of Steel Ring Lining Reinforcement For Metro Tunnel

By the end of 2021,the total mileage of subway operations in mainland China has reached7253.73 kilometers.With the construction and operation of a large number of subway tunnel,due to the influence of improper design and construction in the construction phase,water and soil pressure changes in the operation phase,or aging materials,and with the increase of service time,more and more tunnels have water leakage,segment cracks,large deformation,and track bed voids,which affect the safe and efficient operation of trains,and need to be repaired and reinforced urgently.In this paper,based on the experimental research on the stress of the anchor bonded composite single beam structure,the emphasis is on the study of the mechanical properties of the subway tunnel segment joints strengthened with different steel plate thicknesses and anchor bolt strengths.Combined with the full scale test results of the project in the early stage,the mechanical properties of the tunnel pipe ring reinforced with steel plate lining are studied by using numerical simulation.The specific research content and main achievements are as follows:1.Two point loading tests were conducted on reinforced concrete standard beams reinforced with steel plates to study the effects of the number of reinforced steel plates and connecting anchor bolts on the mechanical properties and failure mode changes of the standard beams,as well as the mechanical performance of the reinforced steel plates.The results indicate that(1)the standard beam reinforced with steel plates first exhibits vertical cracks below the loading point.As the load increases,diagonal cracks begin to appear near the anchor bolts near the mid span and develop towards the loading point.The cracking range of the bending shear section gradually increases,and the width of the diagonal cracks increases until the steel plate and concrete slide relative to each other.After reaching the ultimate load,the specimen fails;(2)As the number of connecting anchor bolts increases,the ultimate bearing capacity of the specimen increases,and the synergistic effect between the steel plate and concrete structure becomes better,but the change is not significant after reaching a certain number of anchor bolts.2.Based on the indoor test method,the tunnel segment element is equivalent to a reinforced concrete beam.With reference to the steel ring lining reinforcement method of subway tunnel,the test beam is post anchored with anchor bolt+epoxy resin+steel plate,and the corresponding model is established using ABAQUS finite element software.The test results and numerical analysis are mutually verified,revealing the mechanical mechanism of anchor bonded steel plate reinforcement of reinforced concrete beams,The distribution pattern of adhesive damage on the joint surface of anchor bonded steel plates has been obtained.The number of anchor bolts can improve the synergistic effect efficiency of the joint surface and effectively improve the ultimate bearing capacity of the specimen.3.For the deep buried segments of the Nanchang Metro,a refined mechanical model of the segment joint was established by simulating adhesive through cohesive contact and simulating the action of a single anchor bolt using embedded beam elements.The mechanical characteristics of the unreinforced segment joint under different internal force states were obtained,and the effects of different reinforcement parameters such as steel plate thickness and anchor bolt strength on segment damage and anchor bolt stress were comprehensively considered,Provide reinforcement basis for engineering practice.4.Based on the above research methods and results,and the full scale loading test results of the previous project,a detailed full scale numerical model of the 3+2+1 segment is established,and the deformation of the reinforced tunnel section under the unloading condition of crustal stress change under the condition of unreinforced and lined steel ring reinforcement is analyzed and compared,revealing the mechanism of anchor bonded steel ring lining reinforcement under the overall elliptical deformation of the tunnel.