Stress evolution and support mechanism of a bolt anchored in a rock mass with a weak interlayer

• Published in: International journal of mining science and technology Vol. 27; no. 3; pp. 573 - 580
• Main Authors: Ding, Shuxue, Jing, Hongwen, Chen, Kunfu, Xu, Guo'an, Meng, Bo
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.05.2017; State Key Laboratory for Geomechanics&Deep Underground Engineering, School of Mechanics and Civil Engineering, China University of Mining&Technology, Xuzhou 221116, China; Elsevier
• Subjects: Deformation process; Fully grouted bolt; Stress evolution; Support mechanism; Weak interlayer; Fully grouted bolt; Deformation process; Stress evolution; Support mechanism; Weak interlayer
• ISSN: 2095-2686
• DOI: 10.1016/j.ijmst.2017.03.024

By applying experimental method, the bolt stress and supporting mechanism is studied during the deformation process of a rock mass containing a weak interlayer. The force measuring bolt is installed manually and instrumented five pairs of symmetrical strain gauges. The experimental results show that the fully grouted bolt suffers tensile, compressive, bending and shear stress at the same time. The bolt stress evolution is closely related to the deformation stages of the rock mass which are very gradually varying stage, gradually varying stage at the pre-peak and suddenly varying stage at the post peak stage. The axial compressive stress in the bolt is mainly induced by the moment. Thus, in most cases the axial compressive stress is distributed on one side of the bolt. For axial stresses, induced by the axial force and the bending moment at the post-peak stage, three types of changing are observed, viz. increasing- increasing type, decreasing-increasing type and increasing-decreasing type. The stress characteristics of the bolt section in the weak interlayer are significantly different from those in the hard rock. The failure models of the anchored bolt are tensile failure and shear failure, respectively. The bolt not only provides constraints on the free surface of the rock mass, but also resists the axial and lateral loading by the bending moment. This study provides valuable guidelines for bolting support design and its safety assessment.