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基于可破碎三维离散颗粒模型模拟了一系列常规三轴试验与真三轴试验,研究了砂土在真三轴应力状态下的破碎行为。数值调查主要关注试样的应力应变特性、级配及相对破碎率的演化。随着围压增大,颗粒破碎率增大,试样应变软化特性和剪胀性逐渐减弱,而超过临界高围压后,由于固结中颗粒大量破碎,试样剪胀性反而增强。真三轴试验中,试样偏应力比峰值均随中主应力参数b值增大而减小。由于破碎随b值增加而明显增大,试样剪胀性随b值增大而逐渐减弱。试样内摩擦角φ随围压增大而减小,其演化关系基本满足对数关系;内摩擦角随b值增大先增大后减小,Lade-Duncan准则较为适合描述其变化规律。此外,试样相对破碎率增大的速率随围压和轴向应变增大而逐渐降低,暗示试样最优终极级配的存在,且相对破碎率与试验输入能量之间存在唯一的双曲线关系。
A series of conventional triaxial tests and true triaxial tests were simulated based on the crushable three-dimensional discrete particle model. The crushing behavior of sand under true triaxial stress was studied. The numerical investigation mainly focuses on the stress-strain characteristics, grading and evolution of the relative fragmentation rate of the sample. As the confining pressure increases, the rate of particle crushing increases, and the strain softening behavior and dilatancy of the sample gradually decrease. When the critical high confining pressure is exceeded, the dilatancy of the sample increases due to the large amount of particles in the consolidation. In the true triaxial test, the peak value of the deviatoric stress of the specimens decreases with the increase of the b value of the main stress parameter. As the crushing increases with the increase of b value obviously, the dilatancy of specimen decreases with the increase of b value. The internal friction angle φ decreases with the increase of confining pressure, and its evolution relationship basically satisfies the logarithmic relationship. The internal friction angle first increases and then decreases with the increase of b value. Lade-Duncan criterion is more suitable to describe the variation law. In addition, the rate of increase of relative crushing rate gradually decreases with the increase of confining pressure and axial strain, indicating the existence of the optimal final grade of the sample, and there exists a unique hyperbola between the relative crushing rate and the experimental input energy relationship.