Quantification of Shape Properties and Their Effects on Particle Packing of Coarse-Grain Soil
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TECHNICAL NOTE
Quantification of Shape Properties and Their Effects on Particle Packing of Coarse-Grain Soil Aijun An1 • Zhihong Nie2
Received: 29 March 2020 / Accepted: 1 September 2020 Ó Indian Geotechnical Society 2020
Abstract Particle shape is known for its significant influence on the engineering properties of coarse grain soil. But it remains difficult to quantify how the different scales of shape properties will affect the macroscopic soil behavior individually. This study aims to select independent shape descriptors at different geometrical scales and evaluate the influence of particle shape irregularities on the particle packing of coarse-grain soil. With the aid of the digital image technique for 2D image acquisition of coarse grain soil particles, the shape properties were firstly quantified by the presented shape descriptors. Statistical analysis was performed to evaluate the independence of each shape descriptor and the most common independent descriptors; elongation, roundness, and texture signature were put forward. The proposed shape descriptors were then used to classify the collected particles and establish the particle shape library. The influence of each scale shape property on particle packing was systematically investigated using discrete element method (DEM) simulations of uncompacted void content test with predefined particles selected from the shape library. The simulated particles with specified shape properties were selected from the corresponding shape library. The numerical simulation results indicated that elongation and roundness significantly contribute to particle packing, while the influence of texture signature can be neglected due to its small variation in nature. The larger elongation and smaller roundness values were
& Zhihong Nie [email protected] 1
China Road & Bridge Corporation, Beijing 100011, China
2
School of Civil Engineering, Central South University, Changsha 410075, Hunan, China
proved to increase the uncompacted porosity of coarse grain soil. Keywords Coarse-grain soil Particle shape descriptor Digital image process Statistical analysis Discrete element modeling Void content
Introduction Particle shape characteristic of coarse-grain soil is an issue of interest in the railway industry where the engineering performances of the embankment filling materials are under highly concerned. In order to better understand the shape effect on macro-scale properties of coarse-grain soil and to predict the filling material performances with different shape irregularities [1], it is essential to characterize the particle shape characteristics in a quantifiable manner. Different imaging techniques (conventional digital photography, optical microscopy) have been employed to capture digital images of soil grains [2]. Various shape descriptors (aspect ratio, sphericity, angularity [3], roundness [4], elongation [5], convexity, roughness, etc.) have been proposed to quantify the particle shape for both fine and coarse grains such as sand, aggregates, and rock parti
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