Assessment of Bolt Reinforcement Effect Based on Analytic Hierarchy Process

The prediction and assessment of bolt reinforcement effect are directly related to the safety of the underground engineering. However, the bolt support effect is affected by multi-factors. In order to evaluate the reinforcement effect comprehensively, the weight of the controlling factors of the reinforcement effect was carried out based on analytic hierarchy process (AHP). The feasibility of the AHP model was verified by numerical simulation. The study indicated that the weight of controlling factors from large to small is: rock grade, geology, bolt diameter, number of bolts, excavation time, rock formation, anchoring length, bolt length, technical equipment, bolt type and construction worker. In addition, two-stage assessment and management methods for bolt reinforcement were proposed, including the preliminary assessment and dynamic controlling assessment. Preliminary assessment is the evaluation of risk surroundings, and it is a risk assessment carried out before the construction scheme. Dynamic assessment is the evaluation of risk surroundings, risk factors and reinforcement background, and it is brought into operation for dynamic risk assessment and management. Moreover, the influence of bolt parameters to reinforcement effect was deeply analyzed. The results show that the diameter of bolts should be controlled within 30 mm, and the length of bolts should be limited within 6 m. Furthermore, the existence of free part along a bolt could improve the reinforcement effect. This research has an important theoretical reference to guide the parameter design of bolt support engineering.