Mechanism And Calculation Of Pre-stress Anchors For Rock Mass Reinforcement

As a reinforcing and supporting technology, pre-stress anchor has been widely used in the reinforcement of water conservancy engineering, water and electricity engineering, railway, highway, industry and civil constructions. It takes a key role to inspire the self-bearing capacity of rock mass, to adjust and improve the stregth and self-stabilization of rock and soil, and to decrease the deadweight of the supporting structure. It also can be used to save engineering materials and assure the safty and stability of the construction, bring to a great economy and social benefit. Because of the complexity of practical engineering, there have many influence factors on the effection of pre-stress anchor and difficult problems in the research of anchor mechanism. Therefore, it is need to take more attention to study the action effection of pre-stress anchor. In this paper, the formulas are derived to describe the stress and displacement fields in the rock mass around the pre-stress anchor head. The multi-anchor effection is studied. The formulas of the stress and the displacement fields in the rock mass around the pull-type and compression-type pre-stress anchorage segments are given. The formulas of the friction stress on the interface of anchorage segment plasm and rock mass are obtained furtherly. In numerical study, the displacement functions and coordinate radiation functions of the 3D 4-node and 8-node dot radiation infinite elements are derived. They are coupled with the isoparameter elements to simulate the action of the pre-stress anchor head and segment. The thesis includes the following contents:(1)Based on Boussinesq equation of the semi-space infinite solution, the theoretical formulas of the extral stress and displacement fields in the rock mass around the pre-stress anchor head are proposed. The distribution shape of the stress, displacement and the influence range of the pre-stress around the anchor head are obtained. The stress characters, distributing rule and influence factors are discussed. The theoretical results are compared with the numerical simulation results by FLAC3D, and agree with each other.(2)Based on Kelvin equation of the infinite space theory, the theoretical formulas of the extral stress and displacement in the rock mass around the pull-type anchor segment are derived. The distribution shape and influence range of the extral stress and displacement in the rock around the pull-type anchor segment are obtained. Furthermore, the theoretical formulas of the stresses and the displacements in the rock mass around the dispersing-pull-type anchor segment are deduced. The theoretical formulas of the friction stresses on the interface of the anchor segment plasm and the rock mass are derived, and the distribution shape are also obtained.(3)Based on Kelvin equation of the infinite space theory, the theoretical formulas of the extral stress and displacement in rock mass around the compression-type anchor segment and the dispersing-compression-type anchor segment are derived. The theoretical formulas of the friction stress on the interface of the anchor segment plasm and the rock mass are derived. The distribution shape and the influence range of the extral stress and displacement in the rock around the compression-type anchor segment are obtained. The distribution rule of the friction stress is summarized.(4)Based on the theoretical formulas of the extral stress and the displacement in the rock mass around the singal anchor head, the formulas of the multi-anchor are derived. The surfacial effection on the rock mass caused by the multi-anchor effection is studied. The results indicate that the effection is a homologous rock-anchor wall on the rock mass surface. The theoretical results are compared with the numerical simulation results of FLAC3D, and agree with each other.(5)The theory of 1D dot radiation infinite element is extended to 3D case. The displacement functions and coordinate radiation functions of the 3D 4-node and 8-node dot radiation infinite elements are derived. They are coupled with 8-node and 20-node isoparameter elements to simulate the displacements of the pre-stress anchor head and segment respectively. The numerial results are compared with the theoretical results, showing that the infinite element method is an effective numerical method to simulate the infinite field problem.