Dr Xuzhen He obtained his bachelor’s degree in Hydraulic Engineering from Tsinghua University (2010), and studied in the University of Cambridge for his PhD (till 2017) with a full scholarship (Raymond and Helen Kwok Scholarship) from the University and Jesus College. In 2015, he received the prestigious John Winbolt Prize from Cambridge.
After working as a Research Fellow in BOKU, Vienna, Austria for two years, he joined UTS as a Research Fellow in July 2019 and will continue to work as a Lecturer from May 2021.
Dr He is interested in the multi-scale multi-physics modelling of geomaterials, the application of mesh-free methods in geotechnics, the application of machine learning or AI in geotechnical designs.
Can supervise: YES
Multi-scale Multi-physics modelling of the geomaterial
- micro-mechanics and Discrete Element (DEM) Simulations
- coupling between DEM and CFD (or SPH, etc)
- 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 dynamically installed anchors
- piles or pipes in soil etc.
AI in geotechnics:
- symbolic regression in computational geomechanics
- adaptive learning and surrogate-based optimization
He, X, Wu, W, Cai, G, Qi, J, Kim, JR, Zhang, D & Jiang, M 2020, 'Work-energy analysis of granular assemblies validates and calibrates a constitutive model', GRANULAR MATTER, vol. 22, no. 1.View/Download from: Publisher's site
Cai, G, He, X, Dong, L, Liu, S, Xu, Z, Zhao, C & Sheng, D 2020, 'The shear and tensile strength of unsaturated soils by a grain-scale investigation', GRANULAR MATTER, vol. 22, no. 1.View/Download from: Publisher's site
Dong, W, Li, W, Guo, Y, He, X & Sheng, D 2020, 'Effects of silica fume on physicochemical properties and piezoresistivity of intelligent carbon black-cementitious composites', Construction and Building Materials, vol. 259.View/Download from: Publisher's site
© 2020 Elsevier Ltd Carbon black (CB) filled cementitious composites as cement-based sensors with intrinsic piezoresistivity have the potential applications for structural health monitoring (SHM). Effect of silica fume (SF) replacement ratio on the physicochemical, mechanical and piezoresistive properties, and microstructure of CB-cementitious composite were experimentally investigated in this study. The results show that 5% or 10% replacement ratio of SF can improve the water impermeability, setting time and electrical conductivity, but decrease the fresh flowability. Cementitious composite with 10% SF exhibiteds excellent compressive and flexural strengths. Moreover, cement hydration in the acceleration stage decreased with the increase of SF content in the early stage, but the phase analysis after 28 days curing demonstrates that with the addition of SF, there are more hydrated products and less ettringite. In addition, the microstructures of cementitious composites without SF present more porous structures and CB agglomerations. In contrast, the amount of micropores or voids was significantly reduced by the addition of SF due to the physical filling effect and less CB agglomerations. In terms of piezoresistivity, SF can obviously improve the fractional changes of resistivity (FCR) under cyclic compression. With 10% SF, CB-cementitious composites as cement-based sensors exhibited excellent FCR and electrical stability, which will promote their development and application in the SHM for smart infrastructures.
He, X, Xu, H, Sabetamal, H & Sheng, D 2020, 'Machine learning aided stochastic reliability analysis of spatially variable slopes', Computers and Geotechnics, vol. 126.View/Download from: Publisher's site
© 2020 This paper presents machine learning aided stochastic reliability analysis of spatially variable slopes, which significantly reduces the computational efforts and gives a complete statistical description of the factor of safety with promising accuracy compared with traditional methods. Within this framework, a small number of traditional random finite-element simulations are conducted. The samples of the random fields and the calculated factor of safety are, respectively, treated as training input and output data, and are fed into machine learning algorithms to find mathematical models to replace finite-element simulations. Two powerful machine learning algorithms used are the neural networks and the support-vector regression with their associated learning strategies. Several slopes are examined including stratified slopes with 3 or 4 layers described by 4 or 6 random fields. It is found that with 200 to 300 finite-element simulations (finished in about 5 ~ 8 h), the machine-learning generated model can predict the factor of safety accurately, and a stochastic analysis of 105 samples takes several minutes. However, the same traditional analysis would require hundreds of days of computation.
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: 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: 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
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.