基于离散元法的真三轴应力状态下砂土破碎行为研究

发布时间：2019-05-16 18:57

【摘要】：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。
[Abstract]:Based on the breakable three-dimensional discrete particle model, a series of conventional triaxial tests and true triaxial tests are simulated, and the crushing behavior of sand under true triaxial stress is studied. The numerical investigation mainly focuses on the stress-strain characteristics, gradation and the evolution of relative fragmentation rate. With the increase of confining pressure, the breaking rate of particles increases, and the strain softeness and dilatancy of the samples gradually weaken, but after exceeding the critical high confining pressure, the dilatancy of the samples increases due to the large number of particles broken in consolidation. In the true triaxial test, the peak value of bias stress ratio decreases with the increase of the middle principal stress parameter b. As the breakage increases obviously with the increase of b value, the dilatancy of the sample decreases with the increase of b value. The internal friction angle 蠁 decreases with the increase of confining pressure, and its evolution relationship basically satisfies the logarithmic relationship, and the internal friction angle increases at first and then decreases with the increase of b value, and the Lade-Duncan criterion is more suitable to describe its variation law. In addition, the increase rate of relative crushing rate decreases with the increase of confining pressure and axial strain, which indicates that the optimal ultimate gradation exists, and there is a unique hyperbolic relationship between the relative crushing rate and the input energy of the test.
【作者单位】：武汉大学土木建筑工程学院;
【基金】：国家自然科学基金项目(10802060,11172216,11472196) 国家重点基础研究发展(“973”计划)计划项目(2010CB731502)
【分类号】：TU441

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