Study On The Detecting Methods Of Prestress Of Prestressed Anchor Rope

As the most economical and effective measure to reinforced rock and soil and steady structure, the technology of ground anchorage win the people favor since the emergence of the technology. Improper construction technology and management will make the prestressed anchor rope into “a time bomb”, which may destroy the engineering in one night. So the anchorage quality of prestressed anchor rope has always been the focus of people, and the effective prestress of prestressed tendon, which is one of the critical parameter of anchorage quality, also get attention of people. The ground anchorage engineering is the long-term and concealed work, which will bring hardship and dilemma to detect the effective prestress of prestressed tendon. It became a topic in front of geotechnical workers to explore a efficient,accurate, economical and practical detecting method. Therefore, this paper studies about the problem.In this paper, the mechanism of prestress loss was studied, mainly the mechanism of prestress distribution and transmission of anchor fixed length, the influence factors of anchor rope failure and the prestress loss. At first, based on predecessors’ research, the shear stress distribution pattern of the first bonding surface and the second bonding surface are studied respectively:the peak value of shear stress of the two surfaces and its position is obviously different; Then, according to the investigation and survey information in hand,the five failure forms of prestressed anchor rope were studied:the failure of anchor head, the broken of tendons, the slip failure of the first first bonding surface, the slip failure of the second bonding surface, the failure of the rock and soil mass; Finally, through the analysis of the influencing factors of prestress loss, theoretical calculating formula of effective prestress was obtained: sde-=NNN0. And it provides reference for establishment of judging criteria for effective prestress.At present, only the summation of prestress is concerned in the detection of prestressed tendons, the uneven value of prestress of each tendon is rare concerned. To address this issue, the unevenness was proposed, and two varying lift-off testing, ALL Tendons lift-off testing and EACH Tendon lift-off testing, were discussed by the means of theoretic and experimental methods. First, the changing law of the stress-strain of prestressed tendon during the testing in detail was analyzed and the special judging criteria for effective prestress was established; Then, according to the engineering practice and theoretical analysis, a new view upon the eligibility criteria of stipulation about the effective prestress in Technical Specification for Construction of Highway Bridge and Culverts was put forward; Finally, the detection precision of EACH Tendon lift-off testing, the unevenness of prestress of prestressed tendons and the eligibility criteria of effective prestress were studied by the mean of simulated test.The paper preliminary discussed the engineering feasibility of Non-destructive testing(NDT), which is based on the acoustoelasticity theory. At first, the determination of acoustoelasticity coefficient and the choice of elastic wave were discussed, which are the two key issues of NDT technology; Next, the processing and analysis of test data validated the feasibility of NDT; Finally, the influencing factor of the detection precision and the detecting process in real project of NDT were discussed.