Study On The Interfacial Bond Deterioration Mechanism Of The Geotechnical Prestressed Anchorage Structure Under Cyclic Load

Because of the advantages such as:small disturbance to the rock and soil mass, fast construction, safety, economical and practical etc, the prestressed anchor technology has been widely used in large scale reinforcement of geotechnical engineering, which include:high steep slope reinforcement, dam reinforcement, deep foundation pit support and mine support etc. this technology has also been creating considerable economic and social benefits. However, due to the inconvenience for the research and testing,which is caused from the deep underground working status of the prestressed anchor cable, its design concept still apply old ideas based on the limit equilibrium principle, what ingores the changes of the prestress itself. But, as a matter of fact, under the impact of the external environmental factors, the tensile of the prestressed anchor cable is in constant cyclic fluctuation in practical engineering. This fluctuation has a severe effects on the interfaces of the inner anchoring section, it is not conductive to the durability of the anchorage structure. Based on the study of other scholars on the cyclic fluctuation law of the tension within the prestressed anchor cable, this paper will research the interfacial bond deterioration mechanism within the inner anchoring section and the development characteristics of the inner microcosmic physical and mechanical parameters, under the action of prestress cyclic fluctuation, from the two aspects of laboratory experimental and numerical simulation. The main research contents are as follows:(1) Researching the interficial bond deterioration mechinism under different stress levels, load fluctuation and grout strength through the laboratory cylic loading test. Measuring the axial strain of the bolt and the shear strain on one interface bewteen the bolt and the grouting and another one bewteen the grouting and the surrouding rock, analysis on the change law of the data obtained along with the number of the cylic loading. To reveal the macro mechnism of bond deterioration of each interface in the inner anchoring section under cylic load.(2) Based on the test results, according to the distribution characteristics of the axial strain within the bolt and the shear strain on the interfaces, preliminary study the quatitative relations of the bond deterioration depth with grout strength, load variation and other factors.(3) Based on the particle flow theory and the PFC2D program, found a mesoscopic mumerical simulation platform for the analysis of the interfacial bond deterioration performance of the geotechnical prestressed anchorage structure. And search the meso mechnical nature of the interfacial bond deterioration from the micro structure evolution level. Establish the relationship between the macro evolution rules of which include the macroscopic interfacial shear stress, bolt axial force and interface crack and the meso parameters which include Particle porosity, coordination number, contact method, the amount of rotation to the particle contact force, etc. To reveal the meso mechanical mechanism of the interfacial bond deterioration under cyclic load.