| Compression dispersion-type anchor involves the installation of a multiple of unit anchors into a single borehole. Each unit anchor has its own individual tendon, its own unit fixed length of borehole, and is loaded with its own unit stressing jack which ensures that the load in all unit anchors is always identical. The total working load of the anchor is beard by each fixed anchor length of all units in staggered depth in the borehole and by means of respective bearing bodies, the tension loads applied to the plastic coated strands are changed into the compression loads on the grout of each fixed anchor length, then the total working load can be divided into several smaller loads and transmitted to the rock mass and soil in different locations in dispersed compression. Compression dispersion-type anchor can be mainly classified into two categories, one of which is that, plastic coated strands in different length are respectively passed through their own bearing bodies and pre-bent as their midpoints to be the shape of "U" , then forming several totally unbonded strand loops, i.e. unit anchor tendon. As the research object in this paper, study is performed on the anchor holding capacity, load-displacement behavior, displacement of the fixed anchor length, strain and bond stress distribution, and the removability of anchor tendon, furthermore, with the aid of analytical solution, the distribution of the bond stress is calculated and analyzed, based on the results of test and analytical solutions, design method is provided in this paper.On-site tests are taken as the main research way in this paper, in which total three trail anchors are installed, each consisted of two units with 4m fixed lengths. Conventional construction techniques have been employed in all procedures such as drilling, fabrication, installation, grouting and stressing. All anchor tendons are removed from the borehole in the end. In the tests, the maximum loads of three trail anchors reach above 600kN, one of which is 650kN, and all anchors are still in good working conditions. As products of the tests, anchor bearing body and a device for strand pre-bending practical for engineering application have been developed.In the on-site test, with loading and unloading in several cycles, load-displacement data is monitored with which the load-displacement behavior and reproducibility are investigated, and according to related specifications, apparent free tendon length of anchor is calculated for assessment of anchorage. At the same time, behavior and some influence factors of displacement of the fixed anchor are analyzed.As the main method of measurement in the tests, some strain measuring points are arranged on the reinforced steel bars of the anchor bearing body. The changes of strain with different loading levels at their locations have been measured, through which range of influence and distribution of strain with loading in grout can be investigated, and corresponding distributions of axial force and bond stress are calculated according to Hooke's Law. Making use of nonlinear curve fitting, distribution equation of bond stress of the fixed unit anchor length is achieved. It is indicated in thetest that the influence of loading to strain in the grout was about in the range of 5~6m, and very weak beyond 4m. The distributions of strain and bond stress in the grout are attenuated in the minus exponential rule.Based on Winkler Assumption and Mindlin's solution of displacement, elastic solutions for distributions of strain, axial force and bond stress are derived, and the influence of mechanical parameters to those are discussed. The elastic solutions are compared with results of testing, which indicate that the solution from Winkler Assumption can be well tallied with the test results.In the end, according to achievements from home and foreign countries in related research and those gained in the on-site test, two design methods for compression dispersion-type anchor are provided in this paper, the first one is experiential des...
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