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.

Hypoplastic constitutive equation based on nonlinear tensor functions possesses a failure surface but no yield surface. In this paper, we consider the numerical integration and FE implementation of a simple hypoplastic constitutive equation. The accuracy of several integration methods, including implicit and explicit methods, is examined by performing a set of triaxial compression tests. Adaptive explicit schemes show the best performance. In addition, the stress drift away from the failure surface is corrected with a predictor-corrector scheme, which is verified by two boundary value problems, i.e. rigid footing tests and slope stability.

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Reasonable design of induced holes on thin-walled structure is beneficial to enhance the crashworthy performance of the structure. In order to improve the crashworthiness of Al/carbon fiber-reinforced polymer (CFRP) tube, the effect of induced holes on the Al/CFRP thin-walled structure was studied, and the Al/CFRP tube configuration with better overall crashworthiness was obtained by multi-objective optimization design method. First, the quasi-static axial compression tests were carried out on the intact Al/CFRP tube and the Al/CFRP tube with induced holes, and a numerical model validated by the experiment was established. Second, the parameters of the induced hole were studied numerically to explore the influence of the induced holes on the crashworthiness of the Al/CFRP tube. It was found that the diameter and number of the induced hole had a great influence on the crashworthiness and energy absorption (EA) capacity. Finally, the multi-objective optimization was performed to optimize the parameters of the induced holes by integrating the Kriging model technique and the nondominated sorting genetic algorithm (NSGA-II). Compared the optimal design with the intact Al/CFRP tube, the first peak load is reduced by 24.32% and the specific EA is slightly improved by 0.68%.

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This paper presents a simple hypoplastic constitutive model for overconsolidated clays. The model needs five independent parameters and is as simple as the modified Cam Clay model but with better performance. A structure tensor is introduced to account for the history dependence. Simulations of various elementary tests show that the model is capable of capturing the salient behavior of overconsolidated clays.