The Study On Long Time Mechanical And Failure Nature Of The Geotechnical Prestressed Anchor

The prestressed anchor structure is being used widely in geotechnical engineering, and makes great economic benefit and social benefit. The former design of the anchor structure, based on the limiting equilibrium, considers the anchor system to be once for all. The long time security problems of employing prestressed anchor technology to reinforce the rocks and soils have not been considered. Actually, geotechnical prestressed anchor structure is affected by many kinds of outside environment in its operation period. The pretension presents periodic cyclic loading feature. This will affect the long time service life of the prestressed anchor structure. Based on the summary of former researches, the paper studied the long time mechanical and failure nature of the geotechnical prestressed anchor, employing in-situ measurement, indoors model tests and numerical simulation. The main content includes the following aspects.(1)By means of the analysis the monitoring data of the actual anchored slope for 6 years, the long time variation law is suggested. The variation feature, the rangeability, and the variation frequency of the pretension for the prestressed anchor system, under the effect of outside environment factors, are settled.(2)The indoor cyclic loading test is adopted to study the relationship between cyclic times and displacement, shear strain on the inner anchoring section of the anchor bolt. The differences of variation law between the displacement via cyclic times, together with the difference of the shear strain development law between the interfaces of the grout and concrete and the grout and the anchor bolt, are compared.(3)Through the analysis of variation law of the shear strain, the intrinsic reason of the shear strain varies with cyclic times is explained. Under cyclic loading, the feature of the shear strain's peak values moves inside and the feature of the gradual progress of failure on the inner anchoring section, are suggested. (4)The numerical model for inner anchoring section of the anchor cable(bolt) is installed with numerical simulate software FLAC3D. By means of the comparison with the indoor static loading test, the reliability of the numerical model has been proved. The study of the failure development law on the inner anchoring section includes 3 aspects:the variation of the displacement, shear stress, and yielding points. Finally, the influences of the variation of the length of the inner anchoring section and the variation of grout bonding strength on failure development law on the inner anchoring section, has been analyzed.