人工模拟堆石料颗粒破碎的分形特性

摘要

人工制备等粒径、不同强度的水泥球颗粒模拟堆石料，进行室内三轴加载试验。依据试验前后颗粒破碎后的粒径分布，采用Tyler等建立的分形模型，研究堆石料颗粒破碎的分形特性，并与Hardin相对颗粒破碎率进行对比分析，探究分形维数表征颗粒破碎程度的可行性。结果表明：排水和不排水条件下得到的结果相似，试验采用的4种水泥含量的试样颗粒在颗粒破碎后的分布特征具有良好的分形特性。同一水泥含量下，随着围压的升高，堆石料分形维数逐渐增大；高围压下，颗粒破碎严重，中间粒径和细粒含量较多，级配更均匀，分形模拟结果与试验结果较低围压下具有更好的线性关系。相同围压下，随着颗粒强度的增大，颗粒破碎程度减小，分形维数随之逐渐减小。通过与Hardin相对颗粒破碎率进行对比可知，分形维数可以很好地表征试样的级配情况，其值越大，级配越良好，粒径分布情况越均匀，颗粒破碎越严重。%Different intensities and equal size of artificial cement balls were prepared to simulate natural rockfill materials,on which triaxial tests were tested. Based on the fractal model established by Tyler,we studied the fractal characteristics of the rockfill materials before and after the parti-cle breakage,and compared it with Hardin rate of particle breakage to explore the feasibility of the fractal dimension characterizing the degree of particle breakage. The results show that the drained and undrained triaxial shear tests on the same conditions are similar,and the particle size dis-tribution after particle breakage of these four kinds of cement contents possesses good fractal characteristics. Under the same cement content,the rockfill fractal dimension increases with the increasing confining pressure;when the confining pressure is high,the particle breakage is seriously, middle size and fines content are large,so the relationship between the results of fractal simulation and the experimental on high confining pressure more linearity than on the low confining pressure. With the increasing of particle intensity,the degree of particle breaking decreasing,and the frac-tal dimension gradually reduces under the same confining pressure. Through comparing with Hardin rate of particle breakage,it shows that,fractal dimension can express the grading situation of the particles well,the larger the fractal dimension is,the more the well-graded of sample is,com-panied by more serious broken particles .