Abstract
Rock bolt support is an effective technique for controlling surrounding rock of deep roadway. The stability of the anchorage body composed of rock bolts and surrounding rock mass is the core in keeping the stability of roadways. In this paper, the UDEC Trigon model was used in simulating uniaxial compressive test on the anchorage body under different pretension loads. The energy equilibrium criterion of the anchorage body under the uniaxial compressive state was proposed. Furthermore, the fracture evolution and the energy dissipation during the failure process of the anchorage body were analyzed. Results showed that before the peak strength, the external work was stored in the anchorage body in the form of the elastic strain energy (Ue). After the peak, energy dissipated through three ways, including the fracture developing friction (Wf), plastic deformation (Wp), and acoustic emission (Ur). Based on the simulation results, the high pretensioned rock bolts can eliminate the continuous tensile fractures in the anchorage body, decreasing the damaging extent of the anchorage body and the energy that was consumed by the following two main approaches: fracture developing friction (Wf) and plastic deformation (Wp). Moreover, the surplus of the elastic strain energy (Ue) and the strength of the anchorage body can be improved. The pretension load had a positive relationship with elastic strain energy and a negative relationship with the anchorage body damage degree. Based on the above research, the transport roadway of the working face 6208 in the Wangzhuang Coal Mine selected tensile rock bolts to establish the high-performance anchorage body. The monitoring data showed that this reinforcement method effectively managed the serious deformation issue of the roadway surrounding the rock masses.
Highlights
In recent years, the depth of coal mining has been increasing at an annual rate of 6–10 m [1]
The UDEC Trigon method was used to study the influence of pretension on the anchorage body strength and energy. e anchorage body model was composed of triangle deformable blocks
According to the standard calibration procedures, rigid calibration and validation were conducted on the input character of the anchorage body and the rock bolts. en, through the Uniaxial Compressive Strength (UCS) test, the anchorage body, and the influence of pretension force was studied. e following conclusions were acquired: (1) High pretension rock bolts can reduce the extent of fractures in the anchorage body, especially the tensile fractures. e damage extent of the anchorage body was reduced, with a reduction of 16.6% with 90 kN
Summary
The depth of coal mining has been increasing at an annual rate of 6–10 m [1]. Wang et al [17] investigated the effect of the anchoring length of the rock bolts and the pretension force on the stability of the anchorage body. It indicated that increasing the pretension force more effectively control the surrounding rock masses. When the anchorage length of the rock bolt was constant, the effective compressive stress area of the surrounding rock mass in the nonanchored section increased with the pretension force. Using the perspective of energy to analyze and explain the mechanical responding characters of the deformational failure in the anchorage body is an effective method. It is expected that the research results can be more representative of the deformational failure rule of the anchorage body
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