I obtained my bachelor’s degree in Hydraulic Engineering from Tsinghua University (2010), and studied in geotechnical group of University of Cambridge for my PhD (2016) with a full scholarship (Raymond and Helen Kwok Scholarship) from the University and Jesus College. In 2015, I received the prestigious John Winbolt Prize from University of Cambridge.
I am interested in micro-mechanical analysis of granular materials, multi-phase modelling of geo-systems and application of mesh-free methods in geotechnics. I am currently working with Distinguished Prefessor Daichao Sheng on the CFD-DEM study of mud pumping. Before joining UTS, I was working as a research fellow in BOKU, Vienna, Austria.
Multi-scale analysis of the granular materials
- micro-mechanics and Discrete Element (DEM) Simulations
Multi-phase modelling of the geo-system
- coupling between DEM and CFD (or SPH)
- mixture theory for modelling soil-water interaction problem
- unsaturated soil mechanics
Application of numerical methods, particularly the mesh-free methods (SPH, MPM) in
- landslides, debris flows
- mud pumping of railway track embankment
- penetration of dynamic installed anchors
- piles or pipes in soil etc
He, X, Wu, W & Wang, S 2019, 'A constitutive model for granular materials with evolving contact structure and contact forcesPart I: framework', GRANULAR MATTER, vol. 21, no. 2.View/Download from: UTS OPUS or Publisher's site
He, X, Wu, W & Wang, S 2019, 'A constitutive model for granular materials with evolving contact structure and contact forces—part II: constitutive equations', Granular Matter, vol. 21, no. 2.View/Download from: UTS OPUS or Publisher's site
© 2019, The Author(s). This and the companion paper present a constitutive model for granular materials with evolving contact structure and contact forces, where the contact structure and contact forces are characterised by some statistics of grain-scale entities such as contact normals and contact forces. And these statistics are actually the 'fabric' or 'force' terms in the 'stress–force–fabric' (SFF) equation. The stress–strain response is obtained by inserting the predicted 'fabric' or 'force' terms from evolution equations into the SFF equation. In the model, the critical state is characterised by two fitting equations and three critical state parameters. A semi-mechanistic analysis is conducted about the change of the contact number and the obtained results are combined with observed phenomena in DEM virtual experiments to give the constitutive equations for the 'fabric' terms. The change of fabric anisotropy is related to the strain rate, current fabric anisotropy and also contact forces. The change of coordination number is induced by two terms related to volumetric and shear deformations, and also an additional term related to the change of fabric anisotropy. The constitutive equations regarding the 'force' terms are also proposed. All the 'fabric' or 'force' terms are modelled to tend toward their critial state value, which agrees with Li and Dafalias's (J Eng Mech 138(3):263–275, 2012. https://doi.org/10.1061/(ASCE)EM.1943-7889.0000324) basic philosophy in their evolution equation for the fabric tensor. These equations along with the SFF equation form a constitutive model.
He, X, Liang, D, Wu, W, Cai, G, Zhao, C & Wang, S 2018, 'Study of the interaction between dry granular flows and rigid barriers with an SPH model', INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, vol. 42, no. 11, pp. 1217-1234.View/Download from: Publisher's site
Wang, S, Wu, W, Peng, C, He, X & Cui, D 2018, 'Numerical integration and FE implementation of a hypoplastic constitutive model', Acta Geotechnica, vol. 13, no. 6, pp. 1265-1281.View/Download from: Publisher's site
© 2018, The Author(s). 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.
Wang, S, Wu, W, Yin, Z-Y, Peng, C & He, X 2018, 'Modelling the time-dependent behaviour of granular material with hypoplasticity', INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, vol. 42, no. 12, pp. 1331-1345.View/Download from: Publisher's site
He, X, Cai, G, Zhao, C & Sheng, D 2017, 'On the stress-force-fabric equation in triaxial compressions: Some insights into the triaxial strength', COMPUTERS AND GEOTECHNICS, vol. 85, pp. 71-83.View/Download from: Publisher's site
He, X & Liang, D 2015, 'Study of the Runout of Granular Columns with SPH Methods', INTERNATIONAL JOURNAL OF OFFSHORE AND POLAR ENGINEERING, vol. 25, no. 4, pp. 281-287.
He, X, Wu, W, Zhang, D & Kim, J 2018, 'On collapse of 2D granular columns: A grain-scale investigation', Springer Series in Geomechanics and Geoengineering, pp. 157-160.View/Download from: Publisher's site
© 2018, Springer Nature Switzerland AG. This study uses the Discrete Element Method (DEM) to investigate the grain-scale mechanisms that give rise to the diverse flow phenomena of granular material, particularly the collapse of granular columns. The small-scale 2D experiments conducted with aluminium rods are used as benchmarks. It is found that the stiffness or the viscous dissipation at the contacts are not important factors to influence the kinetic, but the apparent friction angle is the dominant one, which is contributed by several sources.
He, X, Wu, W, Zhang, D & Kim, J 2018, 'The hypoplastic model expressed by mean stress and deviatoric stress ratio', Springer Series in Geomechanics and Geoengineering, pp. 17-20.View/Download from: Publisher's site
© 2018, Springer Nature Switzerland AG. Over the past several decades, hypoplasticity has been shwon to be a powerful tool to predict the non-linear behaviour of soils. Early hypoplastic models were developed from trial-and-error procedures and these models are usually expressed in a unique tensorial equation regarding the stress tensor. However, most models for fluid-like soil are expressed in the deviatoric stress ratio and the mean stress and these variables are usually modelled differently. This paper presents the hypoplastic model in a new format and written in these two variables. Additionally, parameters of hypoplastic models usually do not have any clear physical meaning and the authors try to investigate the meaning of parameters in the new equations.
Wang, S, Wu, W, He, X, Zhang, D & Kim, JR 2018, 'A stress correction algorithm for a simple hypoplastic model', Springer Series in Geomechanics and Geoengineering, pp. 419-422.View/Download from: Publisher's site
© 2018, Springer Nature Switzerland AG. In this paper, we consider the numerical integration of a simple hypoplastic constitutive equation. The stress drift away from the failure surface is corrected with a predictor-corrector scheme, which is verified by a boundary value problems, i.e., failure process of a homogeneous slope.
He, X & Liang, D 2015, 'SPH study of rapid landslides of cut slopes', Proceedings of the International Offshore and Polar Engineering Conference, pp. 727-734.
Copyright © 2015 by the International Society of Offshore and Polar Engineers (ISOPE). More and more natural slopes are reshaped into cut slopes nowadays and these slopes are prone to landslides. To properly use the land near cut slopes, a method to evaluate the travel distance of cut slope landslides is necessary. This paper firstly reports on the use of SPH method for the simulation of the Fei Tsui landslide, Hong Kong. Then, the influence of geometry of cut slopes is investigated. It is concluded that the soil friction and pore pressure parameters are important in the evaluation of the landslide travel distance. For landslide deposit residing completely at the toe, the volume, slope angle and source angle are important factors for the prediction of travel distance. Conversely, the landslide height and the shape of the landslide mass are insignificant. For landslide deposit residing partially on the slip surface, the detailed shape of slip surface is also important.
He, X & Liang, D 2014, 'SPH study on the influence of shear-rate dependent effects on the flow behaviour of dry granular assemblies', Proceedings of the 11th (2014) Pacific/Asia Offshore Mechanics Symposium, PACOMS 2014, pp. 198-204.
Copyright © 2014 by The International Society of Offshore and Polar Engineers. Phenomenally, the loose soil behaves like a 'frictional material' in most circumstance, so Mohr-coulomb type models are adopted in the modeling. However, these models generally do not consider the shear-rate dependent effect of the MohrCoulomb friction angle. This paper reports on an application of the incompressible Smooth Particle Hydrodynamic method to the dynamics of the dry granular assemblies. The traditional model with a constant friction angle is compared with the modified Mohr-Coulomb model with a shear-rate dependent friction angle, by comparing their predicted runout of dry granular columns.