A method for generating a block system of coarse granular materials that strictly meet gradation requirements

The discontinuous deformation analysis (DDA) method provides unique advantages in simulating the mechanical properties of coarse granular materials. However, the DDA method cannot automatically generate numerical samples of coarse granular materials that can strictly meet the gradation requirements. Therefore, to solve this problem, a new generation method is proposed for generating a block system of coarse granular materials. First, a particle is randomly selected from the basic morphology database and randomly scaled and rotated to match the particle size requirements of the current gradation, based on the relevant requirements for laboratory tests of coarse granular materials. The accumulated particle area will enter the next gradation when it meets the area proportion requirements of the gradation, and this step is repeated gradually from the large particle size group to the small particle size group. Second, the random drop area, which has the same diameter as the coarse granular sample but a height several times that of the sample, is defined. The particles are randomly placed in this area in order of large to small particle size groups, and the requirements of nonoverlapping and noncrossing between particles or between particles and boundaries must be met. When the efficiency of random dropping is very low or even fails, it is important to keep increasing the sample height multiplier. Third, a DDA-based compaction operation is performed to obtain a stable block system with close particle contact. Fourth, a coarse granular material sample that fully meets the gradation requirements is obtained by gradually adjusting the height of the prepared sample. Finally, an example is used to demonstrate the feasibility of the proposed algorithm.