Study On The Anchorage Mechanism And Durability Of Interior Bond Section Of Prestressed Anchorage Cable

Along with the continuously development of our country's economicconstruction and the constantly quickening of urbanization process, the infrastructureConstruction in our country is experiencing a period of fast development. Therefore,large numbers of high slopes and foundation pits are appearing. Prestressed anchortechnology has been widely used in each field of geotechnical reinforcement and hasachieved the tremendous economic and social benefits due to its many advantages,such as the slight disturbance, the rapid construction, the security and its economy.But in the former design of prestressed anchorage structures, the Limitequilibrium theory has been widely used. The anchorage system was considered aspermanent and the problem of durability is ignored. However, the factors that caninfluence the life-span of prestressed anchorage structures have many aspects, whichare closely related to the exterior environment (including rainfall and temperature),anchorage mechanism, and the presence of corrosion medium and so on. Based on theanalysis of factors that can influence the durability of prestressed anchorage structures,the dynamic conception of durability of prestressed anchorage structures is putforward.Firstly, the indoor model tests of similar material and the digital photographydeformation measure system are introduced to analysis the whole sectioncharacteristics, the development mechanism of microscopic displacement and thebreakage mechanism. The change of axis stress of bolt and shearing strength ininterior bond section rock, and the regularity of development and change of the fieldof displacement under the circumstance of single anchor and group anchor arediscussed in emphasis, which also provide the theoretical foundation for lattermicroscopic numerical simulation.Then through a practical engineering, the variation characteristic of stress ofprestressed anchor during the course of construction, long-term operation is analyzed.rhe various factors that can influence the change of prestressing force are discussed,and the basic laws of change of prestressing force are revealed. Additionally, theconception of big circulation and small circulation about the change of prestressingforce is also put forward. Base on the conclusions, taking into account different cyclicloading schemes and amplitude, and adopting the method of indoor model tests of similar material, the durability of interior bond section under the cyclic loading isdiscussed. Through the test, it is found out that the ultimate times under cyclic loadingis featuring index attenuation and the strength of anchorage body also has importantinfluence on the ultimate times under cyclic loading.Particle flow code is an approach to study the characteristics of microscopicmechanics. It can relate the microscopic structure change of soil with themacroscopical strength, deformation and the mutual operation of structures, and it ishelpful to improve people's understanding on essence and mechanism of geotechnicalengineering problems. In this article, the PFC2D is adopted to study the anchoragemechanism of prestressed bolt enduring pulling force. Especially, the microscopiccharacteristic of displacement filed and stress field of peripheral soil mass is discussed,and further reveals the anchorage mechanism of single anchor and group anchor.Through the comparison with finite differential program and indoor tests, theconclusion gained from numerical simulation is proved to be correct.In the sixth chapter, the indoor accelerated corrosion test is adopted to study thedurability of interior bond section under stress and corrosion medium. The influenceof PH value, time and stress level on corrosion quality of unit length is describedquantitatively. Using the Fick second law, the life-span of the grout under theinfiltration of chlorine ion is forecasted. In the end, the measures that can improve thedurability of prestressed interior bond section are put forward from the design andconstruction aspects.Finally, the problems requiring further studies are discussed.