Research On Calculation Method Of Elongation For Pre-stressanchor

As a reinforcing and supporting technology, pre-stress anchor has been widely usedin the reinforcement of water conservancy engineering, water and electricityengineering,railway, highway, industry and civil constructions. It takes a key role toinspire the self-bearing capacity of rock mass, to adjust and improve the stregth andself-stabilization of rock and soil, and to decrease the deadweight of the supportingstructure.Currently pre-stress construction is usually depanded on two ways, strss andelongation, so It takes a key role to calculate the theoretical elongation accurately andevaluate the quality of construction.Currently,there are lack of special theoretieal about the contact problem betweenpre-stress anchor and mortar in bending duct. In this paper, the formulas are derived todescribe the stress and displacement fields in the rock mass around the pre-stress anchor.We systematically propose description method for related parameters and shapecharactering special position of curved pre-stress anchor. In the end of the thesis, theauthor summarize The calculation method of elongation for prestressed anchor. Thethesis includes the following contents:(1) Based on Boussinesq equation of the semi-space infinite solution and Kelvinequation of the infinite space theory, the theoretical formulas of the extral stress anddisplacement fields in the rock mass around the pre-stress anchor are proposed. Thedistribution shape of the stress, displacement and theinfluence range of the pre-stressaround the anchor are obtained. The stress characters,distributing rule and influencefactors are discussed.(2) we describe the characteristics of drilling trajectory by establishing the geographiccoordinate system,relative coordinate system and drill coordinate system. Based ondrilling trajectory of pre-stress anchor, various calculation methods and adaptabilitycondition are derived. Therefore, establishing calculation model of pre-stress anchortrajectory could be realized on the basis of this method.(3) Based on the elastic contact theory analysis and Hertz contact stress calculationmethod, the characteristic of contact problem between pre-stress strand and concrete inbending duct is obtained. The proeessing method that reduce it to two plane contactproblems is introduced: for the contact Problem within the cross-section of duct, a Hertzcontact stress calculation method based on the cushion layer hypothesis is putforward;for the contact problem within the centerline plane,using elastic plane halfspace line load theory the uniform pressure assumption is inaccurate.(4) The calculation method of elongation for pre-stress anchor in linear condition andbending conditon is proposed. In order to analyze the elongation of curved pre-stressanchor accurately, the pre-stress strand is divided into three phases and four states. Inaddition,on the basis of the factors that affect the calculation method the reasons for thedeviation of pre-stress anchor elongation in the actual construction and productionoperations has been point out.(5) Bi Wei highway K93is the first ultra-high highway slope. The high slope is up to176m, ranking highest among the same slope.Its slope radio is1:0.3or1:0.5.Pre-stress anchor is the main reinforcemen manner.