| At present,China’s society is in a state of rapid development,the major cities continue to put forward higher requirements for the development of underground rail transit.With the continuous refresh of the mileage of subway tunnel operation,the increase of service time and the existing technical limitations and construction problems in the construction process,various structural diseases appear one by one.It is urgent to solve the disease control problem of subway tunnel and to develop and innovate the reinforcing technology.CFRP-concrete filled steel tube reinforced subway tunnel overcomes the shortcomings of internal structure reinforcement methods such as weak strength of fiber cloth and complex operation of inner steel ring installation.As a new reinforcement method of tunnel structure,this technology still needs more in-depth and systematic research and analysis.In this paper,we refer to the relevant literature and reference to the current research and application of concrete filled steel tube and CFRP-concrete filled steel tube in engineering.Using indoor test methods,in the framework of stainless steel square tube material,in cement,epoxy resin for filling materials,carbon fiber cloth(tube)to external(internal)reinforced material,the preparation of a group of 34 specimens,by three point bending beam test to load,carried out the CFRP-concrete filled steel tube under different combinations of flexural performance test research.The effect of filling materials and reinforcement materials on improving the flexural performance of CFRP-concrete-filled steel tube was studied.Based on the experimental phenomenon,failure mode and test data,this paper optimized the material type,material dosage and combination form,and the research results are as follows:(1)The pressure-deflection curves of specimens were divided into four stages.Combined with the phenomena in the test process,the pressure-deflection curves of four typical specimens and three failure modes were summarized,and the variation rules of pressure-deflection curves were analyzed by the flexural stiffness formula.(2)The filling,frame and carbon fiber materials of CFRP-concrete filled steel tube are studied.The filling material can improve the bearing capacity of CFRPconcrete filled steel tube specimens and reduce their ductility.The frame material can restrain the transverse deformation of cement in compression zone and thus affect the flexural property of specimen.Carbon fiber material has the effect of hoop on concrete filled steel tube,which can improve the bearing capacity and ductility of specimens.(3)In this paper,the bearing capacity and ductility of specimens are improved by increasing the proportion of carbon fiber material used as the main material.The circumferential carbon fiber material can restrain the transverse deformation of the specimen,while the axial carbon fiber material can slow down the bending deformation of the specimen and the development of cement and steel pipe cracks in the bottom tension zone.(4)Among the 34 groups of tests,the grouted specimens with 35 mm side length stainless steel square pipe and 2mm thick bidirectional carbon fiber cloth have the most significant advantages in bearing capacity and ductility.The bearing capacity of the specimens was improved by grinding the contact surface of stainless steel square tube,bolt fixing and cement mixed with carbon fiber wire.This paper provides valuable reference for the design,optimization and application of CFRP-concrete filled steel tube reinforcement in subway tunnel. |
