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A smoothed particle hydrodynamics code based on micropolar continua for geomaterials is developed for problems involving large deformation and shear strain localization. Two typical geotechnical problems, i.e., biaxial compression test and sand column collapse, are simulated using classical and micropolar model to demonstrate the performance of the newly proposed method. A parameter study is given on the scale effect in the micropolar continua. [ABSTRACT FROM AUTHOR]

Drainage channels with step-pool system are widely used to control debris flow. The blocking of debris flow often gives rise to local damage at the steps and baffles. Hence, the estimation of impact force of debris flow is crucial for designing step-pool channel. Existing empirical models for impact pressure prediction cannot consider the influence of baffle shape. In this work, a three-dimensional smoothed particle hydrodynamics (SPH) study on the impact behavior of debris flows in step-pool systems is presented, where debris material is modeled using the regularized Bingham model. The SPH method is first checked using the results from two laboratory tests. Then, it is used to investigate the influence of baffle shape and flow density. Numerical results show that the impact pressure at the first baffle highly depends on the baffle shape; however, the largest impact pressure usually occurs at subsequent baffles due to the violent impact induced by jet flows. The peak impact pressure at the first baffle initially grows with increasing flow density; however, it starts to drop as density is beyond a threshold. Based on the numerical results, an empirical relation considering the influence of baffle shape is proposed for better prediction of debris impact pressure. [ABSTRACT FROM AUTHOR]

Smoothed particle hydrodynamics (SPH) is a meshless method gaining popularity recently in geotechnical modeling. It is suitable to solve problems involving large deformation, free-surface, cracking and fragmentation. To promote the research and application of SPH in geotechnical engineering, we present LOQUAT, an open-source three-dimensional GPU accelerated SPH solver. LOQUAT employs the standard SPH formulations for solids with two geomechnical constitutive models which are the Drucker–Prager model and a hypoplastic model. Three stabilization techniques, namely, artificial viscosity, artificial pressure and stress regularization are included. A generalized boundary particle method is presented to model static and moving boundaries with arbitrary geometry. LOQUAT employs GPU acceleration technique to greatly increase the computational efficiency. Numerical examples show that the solver is convergent, stable and highly efficient. With a mainstream GPU, it can simulate large scale problems with tens of millions of particles, and easily performs more than one thousand times faster than serial CPU code. [ABSTRACT FROM AUTHOR]

Predictive-corrective incompressible smoothed particle hydrodynamics (PCISPH) is an efficient SPH variation originally developed for computer graphics. Its application in modeling physics-focused fluid flows has not yet been reported. In this work, an improved PCISPH method is presented for physics-focused fluid flow modeling. Different from traditional weakly-compressible SPH (WCSPH) and incompressible SPH (ISPH), PCISPH satisfies the incompressibility requirement at the particle level without a predefined equation of state. The pressure is obtained using an iterative predictive-corrective scheme at each individual particle. The presented PCISPH allows much larger time steps compared with WCSPH. It also avoids the time-consuming solution of Pressure Poisson Equation (PPE) in ISPH. Consequently, the PCISPH has high computational efficiency even with millions of computational particles. To ensure physically correct modeling of fluid flows, we employ several techniques to enhance the accuracy and stability of the PCISPH: (1) the continuity equation is used to predict density, replacing the mass summation approach used in the original PCISPH, (2) numerical diffusion and pressure smoothing are introduced to improve the pressure computation, (3) a generalized boundary treatment approach which can handle arbitrarily complex geometries is employed, (4) an adaptive time-stepping algorithm is used, allowing efficient simulation as well as ensuring stability. The performance of the improved PCISPH is systematically investigated using three standard SPH validation cases. Comparisons between the improved PCISPH and the state-of-the-art δ — SPH are presented. It is found that the improved PCISPH gives numerical results as accurate as δ — SPH, except for having moderate temporal pressure oscillations. However, the numerical results show that the improved PCISPH is approximately five times faster than δ — SPH. The improved PCISPH method shows to be a promising tool for large-scale three-dimensional fluid flow modeling. [ABSTRACT FROM AUTHOR]

In this paper, we present a unified numerical framework for granular modelling. A constitutive model capable of describing both quasi-static and dynamic behaviours of granular material is developed. Two types of particle interactions controlling the mechanical responses, frictional contact and collision, are considered by a hypoplastic model and a Bagnold-type rheology relation, respectively. The model makes no use of concepts like yield stress or flow initiation criterion. A smooth transition between the solid-like and fluid-like behaviour is achieved. The Smoothed Particle Hydrodynamics method is employed as the unified numerical tool for both solid and fluid regimes. The numerical model is validated by simulating element tests under both quasi-static and flowing conditions. We further proceed to study three boundary value problems, i.e. collapse of a granular pile on a flat plane, and granular flows on an inclined plane and in a rotating drum. [ABSTRACT FROM AUTHOR]

A hypoplastic constitutive model is implemented in a smoothed particle hydrodynamics code for the first time. An improved wall boundary treatment is presented for better performance. The proposed approach is first validated by comparing the numerical results with the analytical solutions for oedometer test. Two more problems involving large deformation, i.e., the collapse of sand between two parallel plates and the failure of a homogeneous slope, are analyzed to demonstrate the performance of the proposed method. [ABSTRACT FROM AUTHOR]