Research On Reinforcement Mechanism And Mechanical Characteristics Of Slope Reinforced By Delivery Controlled Anchor Structure

With the advancement of our society, the scale of infrastructure is increasing,geotechnical anchorage technology is widely used in tunnels, side (sliding) slopes, foundationpits, underground caverns, dams, anti-dumping, anti-floating and other engineeringconstructions, which is one of the economical, rational and effective methods to solvegeotechnical engineering problems. The basic principle of geotechnical anchorage is torelying on the shear strength of surrounding soil to pass structure tension or keep the stabilityof stratigraphic excavation surface.The most commonly used anchor at home and abroad is wholly grouted anchor,mechanical action of which is to make the use of bond strength between rod and groutingbody, grouting body and the rock mass to ensure the stability of the soil. However, a lot ofindoor and engineering test data indicate that the distribution of bond stress along the lengthof the anchor is not uniform. Meanwhile, the stress of anchor free section is not uniform,which can not make full use of the bond strength of hole wall in solid strata (free section).Because that the prestressed anchor cable applies prestressed stress on reinforced slope,it greatly limits the deformation of slope being reinforced, but the effect of reinforcement tothe sloped can be reflected after the anchor cable is tensioned, so the play of effect ofreinforcement is slow, which is unfavorable to fight for time to rescue the slope and landslide.Given the existing advantages and disadvantages of wholly grouted anchor andprestressed anchorage cable, combined with the need of rapid slope disease treatment, a newstructure namely delivery controlled anchor is developed, which can make full use of thebond strength of hole wall in solid strata (free section). The anchor consists of two or moreunits of anchor bars, while the each of free section are arranged alternately bond segments andunbonded segments, the bond length of each unit is determined by bond strength between thegrouting hole wall and the grout body, diameter of anchor hole and thickness of soil, eachsegment is coated with butter (or other lubrication preservatives) except the bonding segment,and plastic pipe or PE cannula is corrugated, anchorage segments have the same structurewith existing anchor rod, which can make use of the self anchorage property of reinforcedlayer (landslide or potential sliding mass) to anchor reversely, which can effectively reducethe size of the outer anchor structures.According to the current shortcoming that wholly grouted anchor can not make full useof the bond strength of hole wall in solid strata (free section). The author through relevantlaboratory tests, numerical simulations, and the comparision with wholly grouted anchor,mechanical characteristics and reinforcement effect of the free section of delivery controlledanchor are studied, and the following conclusions can be obtained: (1) Delivery controlled anchor makes use of the self-locking anchorage of slidingformation, and also uses the potential sliding mass to share some of the load, making up theshortage of bond strength of free section. The situation that the outer anchoring structurebears all the reaction force generated by the progressive failure of anchor bar can be avoided,and it also prevents the stress concentration near the reaction force structure, which can resultsin deformation damage at the reaction force structure and the soil near the structure.(2) Through comparative analysis, laboratory tests and numerical calculation results arebasically the same. the distribution of bond stress of the free section of wholly grouted anchoris uneven, it is similar to a single peak exponential curve form; the distribution of bond stressof free section of Delivery controlled anchor is similar to doublet exponential form, and thebond stress distribution is relatively uniform, which can make full use of the bond strength ofhole wall in solid strata (free section).(3) Viewing from the displacement of two different anchors, it can be seen that thedisplacements of delivery controlled anchor is smaller than that of wholly grouted anchor, andthe slope deformation can be restricted much better, which reflects the superiority of deliverycontrolled anchor.