Mechanical Properties Of Rock-Filled Concrete Based On Random Aggregate Placement

Rock-filled concrete is a new type of concrete material,which formed by self-compacting concrete filling rockfill to form a compact structure.Because of its good integrity and high strength,it was often used in large-scale structures.In previous experimental studies,due to the excessive volume of rock-filled concrete,full-scale specimens was impossible to be made to analyze its mechanical properties and failure mechanism.With the research method of concrete random aggregate meso-model,rock-filled concrete was regarded as a three-phase medium composite material consisting of rockfill,self-compacting concrete and bonding interface layer between them.The main contents are as follows:(1)Combining the polar coordinate method with the circular polygon method,a program was complied to generate a two-dimensional convex polygon aggregate model.The quantity of aggregates with all particle sizes in full-graded concrete was calculated by using the Walranen formula,and the random packing process of convex polygon aggregates was realized by using the Monte Carlo method to ensure that aggregates did not intersect or coincide in the placement area.According to this method,bilateral notched concrete beam was established,four-point shear numerical simulation was carried out for concrete beams.Two main and secondary fracture zones were formed at the notches,which were consistent with the failure patterns of digital speckle test,and the concrete damage plasticity model was suitable for simulating the elastic-plastic analysis of concrete materials.The size effect of concrete was verified by comparing three groups of two-dimensional models of cube and prism.(2)The two-dimensional aggregate model of rock-filled concrete was established by using the packing algorithm.The failure process of rock-filled concrete was studied by three-point bending simulation analysis.The meso-simulation results were in good agreement with the stress-strain curve of the test results,with the error less than 5%.Continuous shear failure zone was formed along self-compacting concrete region in the four-point shear simulation.The flexural simulation analysis of rock-filled concrete models with different rockfill ratios was carried out,and the comparison of the simulation results showed that when the rockfill rate was55%,the rock-filled concrete had high compressive strength,good ductility and good overall mechanical properties,which can provide theoretical reference for engineering application.(3)Based on the principle of three-dimensional convex hull,a simplified incremental algorithm program was developed independently to realize the establishment of three-dimensional stochastic aggregate model of rock-filled concrete.The cubic compression simulation analysis of the model showed that the internal failure of the model occurred first at the junction of self-compacting concrete and rockfill body,and then diffused into self-compacting concrete,and the size effect was existed in the rock-filled concrete.The equivalent modulus of elasticity of rock-filled concrete was calculated by the series and parallel models.The analytical solution of equivalent modulus of elasticity of rock-filled concrete was fitted by the least square method with the strength grade of self-compacting concrete,rockfill rate and elastic modulus of rockfill body as variables.The results were compared with the experimental results and the simulation results of different parameters respectively,the error was about 3%.It is verified that the analytical solution of equivalent modulus of elasticity of rock-filled concrete is correct and reliable.It has certain reference value for engineering application.