Experiments On Mechanical Properties Of Bit Expanded Anchor Rod Made By Calcined Coal Gangue Solid Waste Material

Solid waste as anchor grouting material has received widespread attention in anchor rod support engineering.The anchor grout slurry was prepared using calcined coal gangue solid waste as a cementitious material.The mechanical properties of the bit expanded anchor rod with solid waste materials were studied using a comprehensive approach that included XRF experiments,SEM experiments,direct shear tests,and indoor bit expanded anchor rod pull-out experiments.The results provide technical support for the application of solid waste materials in new bit expanded anchor rods.By conducting XRF experiments to analyze the composition of calcined coal gangue,it was determined that it is free from heavy metal pollution.The microstructure of the calcined coal gangue material and its hydration products were analyzed through SEM experiments,indicating that the pores of the hydration products were small and the microstructure of the cementing sand was more compact.Using an orthogonal experiment for slurry proportioning,the optimal ratio suitable for engineering application was selected.The results showed that the calcined coal gangue slurry has good workability,and its compressive strength is approximately 15% higher than that of pure cement specimens.With the aid of a specially designed direct shear box,shear experiments were conducted at the interface between the bit expanded anchor rod made of solid waste material and the soil.The shear stress-shear displacement relationship,interface friction angle,and friction coefficient were obtained.The results indicated that the use of calcined coal gangue material increases the interface shear strength between the bit expanded anchor rod and soil,with an increase in interface shear strength of approximately 4.61% to11.11%.Moreover,the increase in interface shear strength is positively correlated with the increase in soil cohesion and internal friction angle.Using an MTS hydraulic servo universal testing machine,pull-out experiments of the bit expanded anchor rod made of calcined coal gangue and pure cement materials were conducted to obtain the pull-out force-displacement curve and study the failure mechanism of the bit expanded anchor rod.The results indicated that the failure mode of the bit expanded anchor rod specimens is related to the diameter and length of the grouting body,and the bearing capacity is easily influenced by the diameter of the steel bar and the diameter of the grouting body.Compared with pure cement materials,the bonding degree between calcined coal gangue material and steel bar is higher,with an improvement of approximately 15% under the same conditions.