基于尺寸效应的粗粒土单颗粒破碎试验及数值模拟

在外荷载等因素作用下,粗粒土易发生颗粒破碎。对泥岩和砂岩颗粒进行了一系列的单颗粒破碎试验,基于尺寸效应和颗粒破碎分形模型,研究了单颗粒破碎强度、破碎能量及Weibull模量等与分形维数间的关系。利用PFC^3D对单颗粒破碎过程进行分析,并与试验数据对比,验证了数值程序的可靠性;随后扩展到大颗粒粒径,分析了其单破碎强度及破碎能量。结果表明:在同类试验条件下,不同材料所得的分形维数是不同的;不同粒径砂岩的破碎程度均大于泥岩;单颗粒破碎强度具有明显的尺寸效应;单颗粒破碎强度与破碎能量均可通过分形维数与颗粒粒径预测得出;修正后的Weibull模量也可通过分形维数得出;数值模拟结果与试验结果及预测结果基本一致;大颗粒粒径单颗粒破碎强度模拟结果与预测结果基本一致,破碎能量稍有差异,需进一步试验验证。研究成果可为获取大粒径粗粒土的单颗粒强度与变形特性提供参考。

Single-particle crushing test and numerical simulation of coarsegrained soil based on size effect

The coarse-grained soil is prone to particle breakage under external loads and other factors. A series of single-particle fragmentation tests is conducted for mudstone and sandstone particles. Based on the size effect and fractal model of particle fragmentation, the relationships between the fractal dimension and single-particle crushing strength, fragmentation energy, and Weibull modulus are investigated. A single particle crushing process is analyzed using PFC3D and the modelling results are compared with that from the experimental data to verify the reliability of numerical code. The crushing strength and crushing energy of large particle size are then analyzed by numerical models. The results show that the fractal dimensions of different materials are different under the same test conditions. The fragmentation degree of sandstone with different grain sizes is greater than that of mudstone. The crushing strength of a single particle has an obvious size effect. In addition, the crushing strength and energy of single particle can be predicted by fractal dimension and particle size. The modified Weibull modulus can be also predicted by fractal dimension. The numerical simulation results agree with the experimental results and also agree with the predicted results. Besides, the modelling results of the single particle crushing strength with large particle size are also consistent with the predicted results. The crushing energy, however, shows slightly different, which requires further experimental verification. The research results can provide a reference for obtaining the single particle strength and deformation characteristics of large-size coarse-grained soil.