Granular materials exist widely in nature, industry and engineering applications and perform complex mechanical behaviors. Theoretical analysis, numerical simulations and physical experiments were adopted to investigate the mechanical properties of granular systems and to solve the engineering problems.The discrete element method (DME) was proposed in 1970s and has been a practical approach to study the macro and mesoscopic behaviors of various granular materials. Although numerical methods have been successfully applied to the study of basic physical and mechanical properties of granular materials,there are still many challenges in computational granular mechanics, such as the construction of real particle morphology, flow characteristics of granular materials, multi-media and multiscale modelling and high-performance computational algorithms.

This special issue of Computational Granular Mechanics includes of five research papers relating to the numerical methods and some engineering applications of granular materials. The five papers addressed different topics on computational granular mechanics. The first three papers were written by the authors of Dalian University of Technology, Wuhan University and Institute of Mechanics, Chinese Academy of Sciences respectively.The first paper introduces a multi-superquadric model and a poly-superquadric model to construct the complex geometric asymmetric and concave particles in DEM [1]; The next paper analyzes the dispersion behaviors with five Cosserate wave modes to study the wave propagation in the elastoplastic unsaturated granular media [2]; The last paper describes the particleblock replacement approach based on the DEM-FEM coupled model to study the fracture and fragmentation process of continuum media [3]. The last two papers were written by the professors of Belarusian State University. One paper presents a virtual internal bond model based on deformable Voronoi particles for rock mechanics [4]. The other paper develops a mechanicalmathematical model of the negative Poisson's ratio for the locklayered structure to analyze the deformation process of rock massif in discontinuity zones [5].

We would like to appreciate all the authors for contributing their current research achievements on computational granular mechanics, and also appreciate the organization of the Editorial Office of Theoretical and Applied Mechanics Letters. These research papers enable readers to gain basic understandings and insights into the computational granular mechanics relevant to theoretical models and engineering applications.

Shunying Ji is a professor in the Department of Engineering Mechanics State Key Laboratory of Structure Analysis for Industrial Equipment at Dalian University of Technology. He obtained his bachelor, master and doctor degrees from the Department of Engineering Mechanics of Dalian University of Technology in 1995, 1998 and 2001,respectively. He was a post-doctoral researcher at Clarkson University of USA during 2003-2006.Recently, he works on the discrete element method (DEM) and its applications in cold region offshore engineering and soil mechanics. Since 2011, he severed as a full professor in the tate Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics of Dalian University of Technology. He serves as Dean of the DUT-BSU joint Institute of Dalian University of Technology recently. His research interests are mainly concentrated in areas of computational granular mechanics and its engineering applications in polar ship and offshore engineering, ballast dynamics of railway, landing process of lander and return capsule. He also works on the field experiments of sea ice physical and mechanical properties and the field observation of ice loads on ship hull during polar navigations of ice-breakers. His group developed the computational software SDEM based on GPU-parallel algorithm of discrete element method (DEM). Thus software has been applied in various engineering field well. He published over 150 journal papers, three academic books titled as Numerical Modelling of Engineering Ice and its applications (2011), Computational Granular Mechanics and its Engineering Applications (2018 in Chinese version and 2020 in English version).