Particle Breakage Strain Of Rockfill Materials And Its Numerical Simulation

Particle breakage of rockfill materials is serious under high pressure, so the influence of particle breakage on deformation and strength of rockfill can not be ignored in practice. Most of the research works about particle breakage were performed on natural rockfill so far. The triaxial tests of natural rockfill have some disadvantages that particle breakage can not be controlled and particle breakage rate cannot be precisely determined, so it is difficult to conduct such research quantitatively. In order to investigate deeply the mechanism of particle breakage and the influence of particle breakage on deformation and strength of rockfill, a series of triaxial tests were performed by using cement-ellipse-shaped artificial rockfill. The main achievements obtained in the dissertation are as follows.1. A method for preparing artificial rockfill. The ellipse-shaped particles were moulded in various size and strength with cement pastes. Comparing with the existing artificial rockfill materials, the cement-ellipse-shaped artificial rockfill prepared in this dissertation is more simular to the natural rockfill in mechanical properties, and have the merits of regular shape and controllable strength.2. Triaxial tests on the artificial rockfill. A series of triaxial tests including complete triaxial tests, process triaxial tests, isotropic consolidation tests and load-unload cyclic triaxial tests were performed by using artificial rockfill particles with five levels of strength to investigate the characteristics of particle breakage and the mechanism of breakage deformation. By making use of the merits of artificial rockfill, a detailed statistic and sieving analysis of particle breakage was performed.3. Characteristics of particle breakage. Based on the triaxial test results on the artificial rockfill, the characteristics of particle breakage such as the particle breakage pattern, the grain-size distribution, the evolution of breakage rate, the breakage work and so on were analyzed systemically, and the optimizing state line concept of particle breakage was presented.4. Influence of particle breakage on deformation and strength of rockfill. By analyzing the damage and hardening mechanism caused by particle breakage, a formula for evaluating the strength reflecting the breakage mechanism was developed. On the basis of test results of artificial rockfill materials with different particle strength, the breakage volumetric strain of artificial rockfill materials was separated successfully. The test results show that the relationship between breakage volumetric strain and relative breakage rate is unique and can be fitted by a power function.5. A constitutive model considering the influence of the particle breakage. Based on Shen's double-yield-surface elastoplastic model, a constitutive model considering the influence of the particle breakage was developed by introducing the research findings about particle breakage in this dissertation. The modified model can preferably reflect the influence of particle breakage on the mechanical behaviour of the rockfill materials.