孔隙率、级配参数对粉土双轴压缩性状影响的颗粒流分析

针对颗粒流法中颗粒几何参数等对土体宏观力学性质的影响进行了数值模拟,并将数值模拟结果与室内模型试验验证进行了对比。对二维、三维下土体级配及孔隙率进行了理论分析,并提出二维数值试样颗粒数目及孔隙率转换公式。采用PFC2D软件进行了6组参数验证及24组交叉对比(含4组级配、3组孔隙率及2类接触模型)双轴压缩试验。结果表明:孔隙率对土体力学性质的影响大于级配;随着孔隙率增加,土体强度峰值逐渐降低,对应轴向应变增大,体应变则由剪胀性逐渐向剪缩性过渡。当孔隙率较低时,采用线性及Hertz-Mindlin(H-M)接触模型得到的模拟结果均较接近;而当孔隙率升高时,建议采用H-M接触模型,以更好地反映土体到达强度峰值后产生的后续剪胀效应。

Analysis of particle flow for impacts of granular parameters and porosity on silt’s properties under biaxial compression

To analyze the impact of geometrical particle parameters on macromechanical properties of the soil in particle flow method, the conversion formula of the granule number and modified porosity of numerical sample group in the 2D condition was proposed; and the numerical simulation and the laboratory model tests were carried out. It conducted 6 groups of parameter validation tests and 24 groups of variables cross-comparison biaxial compression tests, and included 4 types of gradations, 3 types of porosities and 2 kinds of contact models. The results show that the effect of porosity is larger than that of gradation on soil mechanical properties. With the increase of porosity, the peak value of soil strength gradually decreases; and the axial strains of corresponding points increase accordingly. Compared with the results of the Hertz-Mindlin (H-M) contact model which is focused on the nonlinear relation between the contact force and relative displacement; the results of the linear contact model are more reliable. Meanwhile the behavior of volumetric strain transited from dilatancy to negative dilatancy. And it is suggested when the porosity increases the H-M contact model reflected the subsequent dilatancy effect of soil after peak strength better.