Characterization of mechanical and bonding properties of anchoring resins under elevated temperature
International Journal of Rock Mechanics and Mining Sciences
Resin anchored rock bolts are widely used in the construction and mining industries to support and reinforce underground roadways and openings. However, increasing the depth of underground openings, particularly in coal mines, has presented a challenge for ground control designers due to the rise in geothermal heat and coal seam combustion. This study aims to comprehensively investigate the mechanical properties, microstructure, thermal and curing characteristics of the anchoring resins using Thermogravimetric Analysis, Dynamic Mechanical Analysis, and Differential Scanning Calorimetry tests. Pullout tests were conducted on resin encapsulated rock bolts to quantify their bonding performance at elevated temperatures ranging from 20 °C to 250 °C. The results showed that the mechanical properties of the resins are closely related to the type of curing agent, filler type and size, and curing time. The compressive strength and elastic modulus of the anchoring materials ranged from 51 to 103 MPa. DSC testing indicated that 65–83% of curing can be achieved in 30 min. At ambient conditions, good agreement was found between the compressive and shear properties of the anchoring resins and their corresponding bond resistance force. A heating and pull-out setup was fabricated to analyze the effects of temperature on the bonding performance of rock bolts chemically anchored in underground spaces. The results revealed a reduction in bonding capacity of the bolts by 6.6%–31.3% when the temperature of the environment reached 75 °C and 150 °C, respectively. The anchored bolts maintained up to 62.6% of their bonding resistance when the temperature increased to 250 °C. Temperature profiles measured by the thermocouples along the encapsulation length showed that the heat transition is independent of the resin type and more dependent on the rock bolt specification.
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