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Confirmation of Candidature - Candidate : Amin Motallebiyan

Optimisation of Rock Bolt Ribs According to Geotechnical Conditions
15 MAR 2023
2.00 PM - 3.30 PM

One of the systems widely used for the reinforcement of underground structures after rock excavation is the rock bolt. They are rock-reinforcing tools used to support the unstable rock strata and prevent further deformation by transferring load from unstable rock to intact rock. Fully grouted rock bolts are the most common types of rock bolts which are anchored by resin or cement. When a fully-grouted rock bolt is installed and rock mass starts to displace, the load is conveyed from unstable rocks to the intact rock through interaction between the grouted materials and surrounding rock mass. Factors like rock bolt geometry, mechanical properties of the profile, grout, rock mechanical characteristics, confining stresses, encapsulation length, and hole diameter in the rock, affect the final behaviour of rock bolts. Bolt surface geometries include the rib profile shape, height, angle of wrap, and distance between the ribs, however, among them, rib space and height play an essential role in transferring the load through the rock bolting system. 

Understanding the combining of these factors is necessary to design and make a suitable rock bolt for any ground condition. The axial behaviour of rock bolts can be studied by analysing deformation and stress distribution using the pull and push-out tests. As far as it can be determined and to the best of authors' knowledge, there has been no systematic experimental study optimising the rib heights and distances for various geotechnical conditions including resin and grout encapsulating agents, encapsulation length, and host rock strength which is the subject of this research study. All previous research studies have only focused on limited pull-out tests of rock bolts encapsulated inside steel tubes without considering the effects of the host rock strengths. In addition, the idea of having grooves between ribs to increase the bond resistance is a departure from the current circle of knowledge which is quite pioneering. 

This study will also provide practical knowledge on the load transfer mechanisms of optimised rock bolts and will benchmark the results against the conventional bolt for further geotechnical implementation. In the end, attempts will be made to develop Finite Element Numerical codes incorporating ABAQUS software to simulate load transfer mechanisms of optimised rock bolts and to carry out parametric studies. The results of experimental studies together with the numerical simulations will provide rock mechanics researchers and designers of rock structures with the required knowledge to implement the optimised rock bolt in geotechnical and rock mechanics projects such as urban tunnels, slopes, and underground mines, improving safety and serviceability of rock structures.

For more information, please email the Graduate Research School or phone 0746 31 1088.