Study On Durability Of Segments Mixed Polypropylene And Steel Fiber

At present,the large traffic tunnel across the gulf and the strait continuously appears.Due to the special structure of the underwater shield tunnel in marine environment,the problem of segment corrosion becomes more and more prominent.Although the high-performance fiber segment developed in recent years has been gradually applied to practical engineering,the research results on the durability of fiber segment are still few,it is not clear how the fibers affect the corrosion of steel bars.In view of this,it is of great practical significance to carry out research on corrosion deterioration of fiber segment.Through theoretical analysis,electrochemical corrosion experiment,numerical simulation,this thesis studied the deterioration mechanism of ordinary and fiber segment under erosion environment,established a theoretical model of chloride ion erosion in fiber and ordinary segments,discussed the influences of fiber on the segment failure morphology and reinforcement corrosion.From the angle of the segment bearing capacity,this thesis established a similar time relationship between the indoor environment and the actual environment,and predicted the service life of the segment.The main work and research results are as follows:(1)Based on the existing research results,this thesis discussed the migration mechanism of chloride in segment,established a theoretical model of chloride penetration in ordinary and fiber segments,verified the correctness of the model by the general finite element software,proved the law of chloride penetration in the segment and the effect of fiber on chloride migration.(2)Considering the characteristics of the shield tunnel environment,this thesis carried out the accelerated corrosion test of fiber and ordinary segment under bending and bearing conditions,proved the difference of mechanical behavior between the ordinary and fiber segments,clarified the effect of fiber on internal force,deformation,crack propagation and failure mode of the segment.(3)This thesis carried out the acoustic emission test on the whole process of the corrosion stage and the post-corrosion damage stage under the chloride erosion environment for fiber and ordinary segments,measured the corrosion cracking mechanism and failure mechanism of fiber and ordinary segments,revealed the influence of fiber on the cracking mechanism of concrete and reinforcement corrosion.(4)From the perspective of the bearing capacity of the segment,and with the surface chloride concentration and the chloride diffusion coefficient as the link,this thesis established the time similarity relationship between indoor accelerated test environment and actual service environment by means of numerical simulation and model test,and predicted the service life of the segment under actual service environment.