Mechanical behavior of coal and rock with central hole defects under eccentric loading conditions

Coal and rock masses in mining projects are often subjected to varying degrees of eccentric loading. To analyze the effect of eccentric loading on the mechanical properties and damage evolution law of coal and rock containing hole defects, a biaxial compression test of coal and rock with eccentric loading was carried out with the help of PFC particle flow program. The results show that the peak stress of the coal and rock decreases linearly with the increase of the eccentricity coefficient under different circumferential pressures. The dominant crack pattern is influenced by the relative position of the hole defects to the loaded area. When the hole defects are located within the loaded area, the main control cracks formed pass through the hole defects, and when the hole defects are located outside the loaded area, the main control cracks do not pass through the hole defects. The evolution process of the number of microcracks in concrete under uniformly distributed load and eccentric load conditions can be divided into three stages: the calm period in the initial loading stage, the pre peak propagation period from the crack initiation point to the peak point, and the rapid increase period after the peak.