Experimental Study Of Load Transfer About Tension-type Prestressed Anchor In Clay Layer

As one of the important rock-soil anchoring techniques, prestressed anchor is widely used in engineering field. The average bonding strength is used to designing anchor in current standards and regulations, and the rationality and security is debatable. There has important engineering application value and academic value for research on load transmission mechanism in anchorage section and the performance of service stage about anchor.Considering the part of slip characteristics of interface between soil and induration under loading process, and define the anchorage section consists of the sliding section and elastic section. The shear stress distribution of sliding section presents that sliding friction force distributes linear. For the elastic section, integrating with the Mindlin solution of a point by concentrated force in elastic semi-infinite space, the shear stress distribution differential equation are derived and shows the unimodal curve type.The engineering equivalent elastic modulus of loaded multi-beam steel strand was investigated through the laboratory test, which provides the reliable basis for tension calculation. And the correction factor of off-axis measuring in steel strand was obtained by resistance strain gage, this offers reliable parameter for prestressed anchor field test.The axial strain of anchorage section was obtained from anchor stretch-draw test to the pile anchor supported foundation excavation filled with clay. After the transformation, shear stress distribution law was captured along the anchorage section. Contrasted with the theoretic result, the highly anastomotic results proved that the theoretical analysis is reasonable.Combining theoretical analysis and experimental data, the design value of prestressed anchor in current standard and regulation was corrected through a modification factor, the soil anchor’s working state will be reflected more accurately. The mobilization factor of anchorage section was proposed, and rules and values were found under different anchor working conditions. Combined with standard and regulation, new idea was put forward about acceptance load, criterion of acceptability and practical safety factor in anchor’s acceptance test.The prestressed anchor plays a pivotal role in the rock-soil anchoring, the research results obtained in this article have certain reference for design philosophy, construction and experiment about anchor.