The Anchoring Mechanism Of High-strength Prestressed Anchor And Time-dependent Deformation Analysis Of Bolted Rock Mass

Because of large-scale exploitation in recent years, resource in low location has dried up and the exploitation of coal has extended to the deep location. Along with the increment of exploiting depth and the deterioration of the geological conditions, it becomes hard to control the stability of the surrounding rocks in deep tunnel and support. The common suspension roof support without pre-stressing based on the constant stress field is no longer safe for such engineering. Recently, the popular and receptible supporting form is high-strength pre-stressed bolting (HSPB) with resinic anchoring agent for the deep underground engineering. But the recent anchorage technology is just applied in coal mine in few countries. Its method is only engineering analogy, thus there is no unify academic direction and scientific gist. So it is very important to research the mechanism and time effect of the HSPB technology. This paper based on the deep tunnel suspension roof support project in Hunan coal mine analyzes the mechanism and time effect of the HSPB technology through theory analysis, numerical simulation and in situ experiment. The content of this paper is presented as follow:1,Through the elastic-plastic theory analysis and numerical simulation, study the axial mechanism of the HSPB technology, viz. improving the stress state and the mechanical parameters of surrounding rocks.(1) Simplify the HSPB to be the radial force of the cavern and the improved mechanical parameters in the anchorage zone, analyze the improvement of the HSPB affecting on the surrounding rocks through the elastic-plastic theory analysis.(2) Set up the 3-D numerical model for the deep underground cavern by FLAC3D, study the improvement of the stress of the surrounding rocks and the evolutions of parameters of each anchor (anchorage diameter, anchorage length L, anchorage spacing D, pre-stressing T), and obtain the effects of anchorage parameters on the stress statement of surrounding rocks.(3) Using FLAC3Dsoftware to simulate the compressive experiment of the anchorage rocks under the load conditions of plane strain, study the improvement of the mechanical parameters (compressive strength, modulus of elasticity E, Poisson's ratio, cohesive force c, friction angle) under the influence of different anchor spacing D and pre-stressing T, obtain the evolutions of the mechanical parameters changing with the anchorage parameters.2,Through viscoelastic theory, numerical simulation and in-situ experiment of HSPB, study the time effect of the anchorage zone, viz. the long-term stability of anchorage rock mass.(1) Simplify HSPB to be the radial pressure of cavern and the improvement of mechanical parameters of the anchorage zone, analyze the time effect of anchorage rock mass by the viscoelastic theory.(2) Study the time effect of anchorage specimens and anchorage rock mass through the creep deformation analysis of FLAC3D numerical simulation and the in-situ experiment of HSPB.