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Li G.,China University of Mining and Technology | Li G.,Huaibei Coal Mining Ltd Company | Sun H.,China University of Mining and Technology | Zhang N.,China University of Mining and Technology | And 2 more authors.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2014

Hollow grouting anchor cables(HGAC) integrates tail resin anchorage and full-size grouting anchorage. The shear stress between anchor agent and borehole surface in HGAC possesses distinct pattern compared with that of traditional tension concentrated anchor cables. By simplifying the mechanical model around the grouts and using the analytical solutions of Kelvin problem and Boussinesq problem, theoretical formulas of shear stress of the grouts between anchor agent and borehole surface was derived based on the theory of elasticity. FLAC3D was also used to simulate shear stress distribution around anchor cables pre- and post- grouting. The results showed that the shear stress curve present bimodal distribution along the axial direction of anchor cable. Drawing force has limited effect on the shear stress distribution of the cable tail part. It has been found that shear stress and its concentration of the end anchored segment and the grouting anchored segment were respectively proportional to the pretightening force and the drawing force, while the shear stress and its concentration of the whole anchor cable was inversely proportional to the pore diameter within certain ranges. ©, 2014, Academia Sinica. All right reserved. Source


Li G.-C.,China University of Mining and Technology | Li G.-C.,Huaibei Coal Mining Ltd Company | Ma Z.-Q.,China University of Mining and Technology | Zhang N.,China University of Mining and Technology | And 2 more authors.
Caikuang yu Anquan Gongcheng Xuebao/Journal of Mining and Safety Engineering | Year: 2013

Although high-frequent maintenance work has been performed on roadways affected by multiple overhead mining in Huaibei mining area, these roadways still cannot meet the requirement of normal coal production. Taking II82 gallery in Luling coal mine as an example, we summarized four common failure characteristics, namely the breakthrough of mental net joint, floor heaving, ingression of support leg, and asymmetric deformation of U-steel support based on the comprehensive analysis of engineering geological conditions. The deformation mechanism of roadways affected by multiple overhead mining was studied by theoretical analysis and numerical simulation, enhanced control technology including new hollow grouted anchor cable, high-effective bolt and grouting reinforcement technique was put forward. Field practice shows that the deformation affected by multiple overhead mining can be effectively controlled by using the supporting technology of hollow grouted anchor cable combined with high-effective bolt. Roof-to-floor relative displacement ranged from 126 to 393 mm after mining, which can meet normal production demand with routine maintenance. Source


Li G.,China University of Mining and Technology | Jiang Z.,China University of Mining and Technology | Lv C.,China University of Mining and Technology | Huang C.,Huaibei Coal Mining Ltd Company | And 2 more authors.
International Journal of Mining Science and Technology | Year: 2015

Based on deformation and failure characteristics of the second belt conveyor roadway at level II of Zhuxianzhuang coal mine, laboratory experiments, numerical calculation and field test were adopted to analyze the composition and microstructure of mudstone, the law of mudstone hydration and its strength weakening induced by water, the characteristics of surrounding rock deformation and failure under the action of confined water. Results showed that montmorillonite clay minerals accounted for as much as 76% of mudstone, with a large number of pores existing in the microstructure. Besides, as the molecular structure of montmorillonite changed, mudstone microstructure damage occurred with the macroscopic manifestation of its rheological instability. Weakening degree of confined water on residual strength of mudstone was almost 50%. The instability mechanism of soft rock roadway caused by high confined water is that surrounding rock circulates the process of "fracture-seepage-mudding-closed" twice, which weakens its strength and leads to roadway instability. A combined support technology, namely the, "high-toughness sealing layer + hollow grouting cables + full-length anchoring bolts with deep borehole" was proposed. Based on field observation, the soft rock roadway was controlled effectively, which also verified the effectiveness of new control technology for surrounding rock. © 2015. Source

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