Analysis of stress distribution characteristics of fully anchored bolt based on actual surrounding rock deformation
(2.Key Laboratory of Safe and Effective Coal Mining of the Ministry of Education, Anhui University of Science and Technology, Huainan, China 232001)
(3.School of Mining Engineering, Heilongjiang University of Science & Technology, Harbin, China 150022)
(4.Zhongtian Hechuang Energy LLC., Ordos, China 017020)
【Abstract】During the supporting process of a fully anchored bolt, the interaction between the bolt and the surrounding rock will cause the stress distribution of the bolt to change. In order to explore the stress distribution of the bolt in the normal supporting process and critical failed supporting process, the interaction model of the anchored bolt–surrounding rock is established based on the deformation of surrounding rock. The analytical expressions of axial force and shear stress along the length of the bolt during the normal supporting process and critical failed supporting process are derived. Furthermore, the distribution curves of axial force and shear stress along the length of the bolt are obtained. Also, the effects of rock conditions, anchor length, and tray anchoring force on the stress distribution of a fully anchored bolt are analyzed under the consideration of anchorage parameters such as the moduli and cross-sectional areas of the bolt and the anchoring agent. The results show that during the normal supporting of the fully anchored bolt, the stress distribution of the bolt body conforms to the neutral point theory. The factors affecting the axial force and shear stress distribution of the anchor include surrounding rock conditions, anchorage parameters and tray anchoring force. During the normal supporting process, the stress distribution of the fully anchored bolt body conforms to the neutral point theory. As the surrounding rock becomes softer, the neutral point moves to the orifice, and the axial force and shear stress increase. Tray anchoring force affects the stress distribution of the bolt body. The greater the anchoring force, the more uneven the axial-force distribution. In addition, the shear stress from the orifice to the neutral point becomes lower, while that from the neutral point to the bolt end becomes higher. Therefore, in the actual project, the tray anchoring force can be monitored in real time. The theoretical basis of this paper can reveal the force characteristics during the bolt supporting process. In the critical failure of bolt supporting, the harder the surrounding rock, the higher the shear stress and the axial force and the more concentrated the stress distribution. The length of the bolt affects the supporting performance of a fully anchored bolt, but the increase in the bolt length after the bolt length exceeds a certain range does not significantly improve the anchoring effect of the anchor bolt.
【Keywords】 fully anchored bolt; stress distribution; neutral point; surrounding rock condition; tray anchoring force; length of bolt;
(Translated by HAN R)
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