Abstract：Particle grading is one of the key parameters affecting the mechanical properties of roadbed fill. The traditional sieving method is difficult to refine and quickly determine the sandy soil particle group due to the large interval between sieve diameters. A new method for estimating the sandy soil particle gradation based on image scanning and mean sampling technology is proposed. The method is based on the scanning electron microscope(SEM) and image processing software ImageJ joint testing technology to determine the geometric parameters of the sand particle morphology. The difference in the distance between any two parallel tangent lines of irregular particles on the projected image contour, namely the Feret diameter as the equivalent diameter of an ideal sphere is discussed, and the equivalent area and volume equations for a single sand particle are established. Based on the general rule that the relative density of sand particles gradually increases with the decrease of particle size, a negative power function model between sand particle size and relative density is fitted, and a function expression for the mass and particle size of a single sand particle is established. Finally, the accuracy of the arithmetic mean method and mean sampling method for sand particle grading is examined by sieving method. The results show that the relative error of ImageJ in identifying sandy soil particles of millimeter level and below depends on the difference between particle size and scale length, that is, when the particle size is smaller than the scale length, the larger the difference, the lower the measurement accuracy. When the particle size approaches or exceeds the length of the scale, the measurement accuracy is higher and more stable. The arithmetic mean method shows strong randomness and is not suitable as a basis for determining the grading parameters of sand particles. The grading curve of sandy soil particles obtained by the mean sampling method with short diameter is the most consistent with the results of the sieve method, which can be used for the estimation of sandy soil particles grading parameters, followed by average diameter, long diameter. The new method can arbitrarily divide sand particle groups and obtain relatively accurate grading parameters, with reliable results and convenient operation.
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2024, Vol. 45 
