CAJ | 학술논문

为分析砂土的剪切力学特性,采用离散元商业软件PFC2D对单粒组密砂在直剪试验中出现的剪切带进行了数值分析.改进传统的分条带观察方式,采用矩形格分割法观察试样内部不同区域的变形特性.对离散元商业软件进行了二次开发,实现了大小主应力及其应力主方向角的可视化,分析了试样内部的应力偏转情况.同时,以纯转动率和颗粒速度等微观变量为中心,观察了试样内部颗粒的运动状态,解析了直剪试验中砂土剪切带形成的微观机制.研究表明,直剪试验中应变局部化区域集中在剪切面附近的一个条带内.通过转动场和速度场的分析可知,剪切带宽度约为10～15倍的砂土平均粒径,带内颗粒转动明显,带边缘出现大的速度和转动变化梯度.对组构和接触力分布的分析可知,剪切过程中粒间接触点和接触力的主轴方向发生了相一致的偏转,偏转后的主轴方向为60°左右.
위분석사토적전절역학특성,채용리산원상업연건PFC2D대단립조밀사재직전시험중출현적전절대진행료수치분석.개진전통적분조대관찰방식,채용구형격분할법관찰시양내부불동구역적변형특성.대리산원상업연건진행료이차개발,실현료대소주응력급기응력주방향각적가시화,분석료시양내부적응력편전정황.동시,이순전동솔화과립속도등미관변량위중심,관찰료시양내부과립적운동상태,해석료직전시험중사토전절대형성적미관궤제.연구표명,직전시험중응변국부화구역집중재전절면부근적일개조대내.통과전동장화속도장적분석가지,전절대관도약위10～15배적사토평균립경,대내과립전동명현,대변연출현대적속도화전동변화제도.대조구화접촉력분포적분석가지,전절과정중립간접촉점화접촉력적주축방향발생료상일치적편전,편전후적주축방향위60°좌우.
In order to analyze the shear behavior of sands, a numerical investigation was carried out on the shear band of ideal dense sand in direct shear test using PFC2D. The traditional band observation method is replaced by a new method , by which the sample is painted into square grid to observe sample deformation pattern. The discrete elements commercial software PFC2D is improved to visualize principal stresses and their inclinations in the sample. Averaged pure rotation rate(APR) and particle velocity are observed to describe the sample with aim to analyze the micro mechanism of the strain localization in dense sand. The study shows that in direct shear test, the strain is concentrated in a band near the shear plane, whose thickness is 10 to 15 times of d50. The particles in the shear band demonstrate significant rotation. Higher gradients are found in velocity and rotation fields on the edge of the shear band. The observation on the contact fabric and contact force shows that principal directions of contact points and contact forces rotate in the similar way with their inclination direction about 60° to the horizontal direction.