Influence of surface rib parameters of bolts on anchoring performance and optimization

Abstract

Deep coal mining rock support structures using rock bolts face complex geological conditions such as high ground temperatures and groundwater. Rock mass deformation and failure caused by bolt failure frequently occur, making it crucial to enhance the anchoring performance of rock bolts. First, the stress state of the anchor rod under axial loading across five stages of any anchored segment is analyzed. The shear stress patterns at the anchoring interface during different stages are elucidated. A refined mechanical model of the anchoring interface incorporating surface rib parameters is established. A failure criterion for the anchoring interface under the influence of ground temperature or groundwater is derived and validated. Second, the influence of anchor rib parameters on anchoring force is analyzed, and in-situ shear tests are conducted. Results indicate that increasing the rib angle and optimizing rib spacing can enhance anchoring force. To minimize the shear component of axial force at the anchor interface, the rib angle of the anchor bolt should not be less than 70°. When the anchor grout possesses high inherent strength, the spacing between ribs on the anchor bolt surface may be increased (to 24 mm or greater). Finally, methods for enhancing the anchoring performance of bolts in deep complex strata are proposed, providing technical references for the safe and efficient support of tunnel rock masses in similar geological conditions.

Keywords

geotechnical engineering / anchorage support / anchorage interface / resin anchoring agent / surface rib parameters / anchorage performance optimization

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Funding

Natural Science Research Project of Anhui Educational Committee(2022AH050814)

Open Fund of State Key Laboratory of Nuclear Resources and Environment (East China University of Technology)(2022NRE07)

National Natural Science Foundation of China(51964002)

National Natural Science Foundation of China(52174104)

Open Fund of Engineering Research Center of Underground Mine Construction of Ministry of Education(JYBGCZX2022105)