| Prestressed anchor is widely applied in geotechnical engneeringreinforcement with some types。This paper mainly study Compressiondispersion-type prestressed anchor。Compression dispersion-type prestressed anchor comes forth as anew type pressed anchor for project requirement in these years,it has itsown unique advantages.It involves the installation of a multiple of unitanchors into a single borehole。Each unit anchor has its own individualtendon,its own unit fixed length of borehole。 The total working load of theanchor is beared by each fixed anchor length of all units in stepped depthin the borehole and by means of respective bearing bodies,the tensionloads applied to the plastic coated strands are changed into thecompression loads on the grout of each fixed anchor length,then the totalworking load can be divided into several smaller loads and transmitted tothe rock mass and soil in different locations in dispersed compression,which adapt weak and cracked uneven stratums.It has these advantagesas follows:1, The peak value of internal force clearly is reduced anddistribute more evenly as a result of distributed load.2, Fixed anchor length of all units in stepped depth in theborehole fully uses stratum's own strength and provide more biggerbearing force.3, Special classifying compensated tension effectively controlsprestress loss.4, The sole grouting simplify the working procedure of groutingand quicken project's progress.5, Unbonded steel cable enhances anchor's antisepsis andlengths its life.6, It retrench material and reduce the cost of project.Central institute of construction of metallurgical industry and OVEEngineering Ltd Coof Liuzhou and so on study Compressiondispersion-type prestressed anchor in theory and test, and deduce someconclusions。 I carry through testing and theoretical simulative researchfor more knowledges about this type of anchor。On-site tests ,threetesting anchors are made respectively up of three units with four meterfixed length 。 Through tension test , load-displacement behavior isanalyzed,we educe:1, Three anchors have different structure,but the way of loadingis different.From test's datum we may see they are in elastic deformationwith little plastic deformation and vary steadily.2, Peak values of the second anchor and the third anchor are inline roughly which indicate tension's elastic status.The first anchor is inline initially,but rock-soil's deformation behind loading board induce lastlater peak values have some distance from line,plastic deformation has atrend of increase.3, From the tension graph of anchor,we may see that graphreappear well.On the basis of datum measured by strain piece,we may educe:1, Strain-load graph is mild and sleek at lower load,axial strain ofgrouted body of two units increase following upon load's increase;strainincrease remarkably in the one-meter's scope of load board hereabout,which carry major load.2, Peak values of strain in the fixed anchor length appear aboutloading pallet,reducing remarkably in the dimention of one meter followingdistance increasing from loading pallet,out of that scope reductionbecome slow and strain's value gradually reduce to zero in the distance offive to six meter from loading pallet.3, By contrast with the status of strain of different anchor roundloading pallet in the same of load,we find their difference,which indicatethat grouting quality have some disadvantages and stratum also havesome difference.4, In test,we find that different tension procedures influence eachunit's load,firstly tensing the first unit induce increase of strain value of thesecond unit,moreover the second unit's tension make the first unit'spressing strain reduce because of tensile strain produced by the seconduint's tension behind the second loading pallet;by contraries,influence islittle.Apparent free tendon lengths of anchors and elastic displacement arecalculated and testify these anchors safe and steady.we deduce theexpressions of axial force ,strain and bonded stress in the fixed sectionsof compression dispersion-type prestressed anchors in theory.Accordingto these expressions we analyze the influencing factors of internal force offixed anchor length such as the ratio of grouting body's and rock-soil'selastic modulus,radius of grouting body,fixed anchor length and frictionangle of interface between grouting body and rock-soil.We simulate the model of reinforcement by Compressiondispersion-type prestressed anchor with finite-difference,and make theseconclusions as follows:1, Peak value of displacement,stress and strain mainly distributein the scope of half one meter about loading pallet,and their value andscope increase following load's increase.2, The distributions of displacement , stress and strain aredifferent from sole units's distributions in the way of size and scopebecause of overlay.Their values in overlay section increase if they aresame kind,otherwise they reduce.3, Rock-soil behind loading pallet is in a tensile way,so aopposite peak value come into being.By contrast with pertinent research in country and abroad,field test'sand analytical results, we testify theoretic analysis right,and bring forwarddesign method of compression dispersion-type prestressed anchor,whichprovide some important theoretic gists.
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