Design Optimization of Aggregate Grading for Coal Gangue Paste Piping Backfill
The aggregate grading is a key parameter in the design of cemented paste backfill.In re-sponse to the problem that original coal gangue is coarse and cannot be directly used for preparing coal gangue paste,research on crushed coal gangue grading design and optimization for backfill are performed through laboratory experiments and hydration simulation.The results show that the dry density of coal gangue sampled on site is 1.614 g/cm3,with a specific gravity of 2.518.More than 70%of the particle diame-ter is greater than 1 mm,belonging to block stones and gravel,and the grading is unreasonable.Using the Taibol theory to design the grading of crushed coal gangue,within the Taibol index range of n is 0.3 to 0.7,the packing density of the crushed coal gangue has a parabolic relationship with n.When n=0.35,the de-signed crushed coal gangue aggregate has the maximum packing density of 2.222 g/cm3,with fine particles below 75µm accounting for 14.2%,which can meet the preparation standards of the paste.There is a clear linear relationship between the Taibol index n and the featured particle diameter,while the relationship for curvature coefficient cc and the non-uniformity coefficient cu is not significant.Using VCCTL hydration simu-lation software,it is verified that the hydration degree of coal gangue paste with the grading of n=0.35 reached 0.78 after 28 days.The microstructure of the paste was denser,with higher predicted mechanical properties,which are related to the filling and nucleation effects of fine particles.The rationality of gradation optimization design is verified from the perspectives of indoor experiment and hydration simulation.The study provides an important theoretical basis and guiding significance for the design and optimization of coal gangue paste fill.
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