The Application Of Discrete Element Method On Filling Performance Simulation Of Self-compacting Concrete In Rfc

RFC (rock-filled concrete) is a new type mass concrete construction technology. The property of the RFC mainly depends on the flow performance and filling capability of SCC (self-compacting concrete) used in the pouring process. The purpose of this study is the flow process simulation of the SCC during RFC casting, in order to pridect the flow behavior of SCC and the compactness of RFC. In this dissssertation, DEM (discrete element method) is adopted, and the study of contact detection algorithm and DEM constitutive model are conducted.The contact detection is the most time-consuming part in the DEM simulation. During the DEM simulation of flow performance of large-scale SCC, contact detection among elements is critical for improving computational efficiency of the DEM. A new area contact detection algorithm named HACell was developed by dividing the space into a hierarchy of cells. The results of contact detection of the 3D discrete element system shows that the only O(N) computation is required. The computational cost is only about 30% of the triditional CGrid algorithm, which means that the high efficient contact searching among discrete elements has been achieved, and makes the DEM suitable in the numerical simulation.The DEM constitutive model of SCM (self-compacting mortar) and SCC is proposed. The reheological parameters of SCM element are used in the simulation of flowability and viscosity of the real SCM. A DEM simulation software has been developed, and the determination method of the parameters has been proposed based on the property tests of SCM. SCM with different properties were simulated. Feasibility of the simulation was validated by observing different types of unconstrained SCM free flows.When SCC flows through obstacles, it is deformed and the restraint makes the flow process complex, which makes the flow performance of SCC mainly affected by the friction behavior of SCM. Based on the load analysis of SCM between coarse aggregate particles during the complex flow process, the friction behavior of SCM is studied experimentally. Shear experiment of SCM paste among sand particles is conducted, and the engaging factor f e is proposed to modify the DEM contact model of SCM. The simulation result agrees well with the experiment result, which shows that the contact model considering engaging factor f e could simulate the friction behavior of SCM properly.Finally, the simulation of the pouring process of the RFC is conducted to verify the DEM constitutive model of SCC. Via the experimental and numerical study of the complex flow process of real SCC, the DEM constitutive model of SCC proposed above has been verified. The simulation results agree with the experiment results. The contact model of SCC considering engaging factor and the determination method of reheological parameters proposed in this dissertation could be used to simulate the complex flow process of SCC during RFC construction properly.