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Introduction
Prof. Wu is the director of the Institute of Geotechn. Eng. at the Universität für Bodenkultur, Vienna, Austria. Prof. Wu is the editor of "Acta Geotechnica". He serves as editor for “Springer Series in Geomechanics and Geoengineering”. He has coordinated some large research projects, e.g. the ITN project on "Multiscale Modelling of Landslides and Debris Flows" (http://www.mumolade.com/). Before his academic career, Prof. Wu worked with leading engineering firms in Europe for more than 10 years.
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Education
October 1986 - October 1992
Publications
Publications (340)
Modelling the cyclic response of granular materials is key in the design of several geostructures. Over the years, numerous constitutive models have been proposed to predict the cyclic behaviour of granular materials. However, pertaining to the hypoplastic constitutive models, one of the significant limitations is their inability to accurately pred...
We propose a smoothed particle hydrodynamics (SPH) model bridging the gap between solid‐ and fluid‐like behaviour observed in granular materials. The key innovation of the proposed approach lies in the decomposition of the stress gradient into rate‐independent and rate‐dependent parts, which are governed by the hypoplastic and constitutive relation...
In this study, an advanced hypoplastic model incorporating the critical state is integrated into smoothed particle hydrodynamics (SPH) for the numerical investigation of geotechnical large-deformation problems. Moreover, a return mapping strategy is proposed to regulate the stress state to avoid calculation failure. Furthermore, a closed-form solut...
This study introduces an SPH (Smoothed Particle Hydrodynamics) model that utilizes mixture theory to address the complex interactions between soil and water dynamics. The model incorporates an intrinsic density formulation for the fluid phase and accurately accounts for the spatial and temporal variations in soil porosity. To discretize the fluid a...
In this paper, we use a phase-field model with the mixed-mode fracture driving forces to study the brittle failure in rockslides. Our phase-field model is capable of predicting the crack initiation, propagation, and coalescence in rock/rock-like materials under different loading conditions. The phase-field model is validated against the experimenta...
The impoundment of Three Gorges Reservoir in China has adversely influenced the stability of the landslide by periodic water level fluctuation, which has been a worldwide issue. The hydrologic action has induced changes in the seep-age field and deterioration in sliding zone soil. Taking the Huangtupo landslide as a case, this study experientially...
Bleeding in fresh concrete refers to the rise of excessive water as a result of sedimentation and consolidation of the aggregates. Various machine learning models are applied in this study to predict the amount of bleeding water based on centrifuge model tests on concrete bored piles. The soil type, its consolidation, concrete age and exposition cl...
Since the first impoundment of the Three Gorges Dam in China, the yearly fluctuations of the reservoir water level have reactivated several landslides. In this study, the stability of the Huangtupo landslide, one of the largest in the Three Gorges Reservoir region, is investigated with a probabilistic approach. The inherent uncertainty of the shear...
This book offers a glimpse of the geotechnical research activities at BOKU, Vienna, in 2023. The research topics are wide-ranged including laboratory testing, constitutive modelling, numerical simulations with DEM and SPH, landslide, tunnelling and machine learning. Many research activities are carried out by visiting scholars from China.
Tunnelling-induced settlement is usually estimated based on field data. However, the data are representative of the local study area only depending on such parameters as geology setting and tunnel geometry. Moreover, the number of training data samples is also limited. In this study, surrogate models are developed to account for the variation of th...
In this work, smoothed particle hydrodynamics (SPH) is employed to investigate the segregation evolution in granular flows. We first provide the Lagrangian description-based governing equations, including the linear momentum conservation and the segregation–diffusion equation. Then the hybrid continuum surface reaction scheme is introduced to formu...
In this work, an advanced hypoplastic model incorporating the critical state is integrated into smoothed particle hydrodynamics (SPH) for numerical investigation of problems with large deformation. This numerical method performs well in cases of element tests such as oedometer test, simple shear test and plain strain compression test, which usually...
https://www.icevirtuallibrary.com/doi/10.1680/jgeot.16.P.233
A novel SPH model aimed at solving the coupled water-soil problems is proposed based on the mixture theory. This method is featured with the spatially overlapped dual continua for both fluid and solid phases. The water phase is modeled as a weakly-compressible Newtonian fluid, and the soil phase is modeled using an elastoplastic constitutive model....
Inherent anisotropy is often observed in natural clays. This paper presents a hypoplastic constitutive model to describe the inherent anisotropy of normally and overconsolidated clays. A stress transformation technique is used to include the nonlinear failure criterion. A fabric tensor for inherent anisotropy is introduced, and its evolution provid...
This paper deals with the numerical simulation of initiation and propagation of mixed mode fracture in rocks. A bond-level energy-based peridynamic model is developed by introducing a dilatation function to capture both volumetric and deviatoric deformations. We proceed to define the nonlocal stresses to obtain the isotropic and deviatoric forces c...
Estimating the failure probability of rainfall-induced landslides is often challenging as the triggering mechanism is influenced by a number of parameters whose uncertainty is difficult to quantify and, in practice, is neglected. The reinforcing effect of vegetation on natural slopes adds to the complexity of the stability analysis. In this study,...
This paper proposes a regularized smoothed particle hydrodynamics (SPH) scheme to solve the problems of tensile instability and stress noise in large deformation soil–structure interaction. Particle shifting and stress regularization are combined to maintain uniform stresses and particle distributions. A generalized frictional boundary condition is...
We formulate a modified phase-field model for cohesive interface failure in quasi-brittle solids. Our model has two novel features: (i) a traction-separation-damage law for damage process; (ii) an energetic degradation function controlled by critical gap ratio. This modification offers an attractive approach to simulate the cohesive interface failu...
In tunnel excavation with boring machines, the tunnel face is supported to avoid collapse and minimise settlement. This article proposes the use of reinforcement learning, specifically the deep Q-network algorithm, to predict the face support pressure. The algorithm uses a neural network to make decisions based on the expected rewards of each actio...
In tunnel excavation with boring machines, the tunnel face is supported to avoid collapse and minimise settlement. This article proposes the use of reinforcement learning, specifically the Deep Q-Network algorithm, to predict the face support pressure. The approach is tested both analytically and numerically. By using the soil properties ahead of t...
We present a new phase-field formulation for the formation and propagation of a compaction band in high-porosity rocks. Novel features of the proposed formulation include (a) the effects of inertia on the rate of development of compaction bands, and (b) degradation mechanisms in tension, compression, and shear appropriate for dynamic strain localiz...
The strength reduction method is often used to predict the stability of soil slopes with complex soil properties and failure mechanisms. However, it requires a considerable computational effort. In this paper, we make use of a convolutional neural network to reduce the computational cost. The factor of safety of 600 slopes with different inclinatio...
In this study, analytical solutions are developed to assess the hydraulic and structure responses of underwater tunnels by considering the tidal loading in conjunction with water ingress. Two scenarios are considered, that is, the surface water fluctuation (SWF) and groundwater variation (GWV). A single-step scheme is put forward to obtain the exac...
Smoothed particle finite element method has been gaining recognition as an appropriate approach for large deformation problems in geotechnics. This paper presents formulations for coupled large deformation problems in geotechnics within the framework of SPFEM. Emphasis is put on the incompressibility associated with the undrained limit. To stabiliz...
In this paper, we investigate the performance of a compressed air energy storage (CAES) pile in overconsolidated soils through finite element analyses. A hypoplastic constitutive model is used to account for the over-consolidation effects of the soil surrounding a CAES pile in a plane-strain model. The numerical results show that the normal force o...
Natural soils usually exhibit microstructure effects that significantly influence their engineering properties; however, existing hypoplastic constitutive models rarely consider structural evolution during loading. This paper presents a hypoplastic constitutive model for structured soils. A structural factor that combines the initial structure degr...
We propose a numerical procedure to locate the critical slip surface of slopes with the method of slices. We employ the Deep-Q Learning algorithm with experience replay and target memory to determine a non-circular slip surface. The overall stability analysis is performed with Janbu's simplified method. Our approach, however, is flexible and can ac...
Residual state rate effects of shear-zone soil regulating slow-to-fast transition of catastrophic landslides
In this work, a three-dimensional multi-layer SPH method is presented for generic water–soil dynamic coupling problems. Based on the mixture theory, two mathematical models using the apparent and intrinsic fluid densities are formulated. Compared with models from literature, our models correctly consider the spatial and temporal change of soil poro...
Catastrophic landslides with basal shear zones usually involve a number of mechanisms that are poorly understood. One mechanism issue is the transition from slow sliding to fast movement, leading to catastrophic failure. We perform laboratory experiments on landslide shear-zone materials to investigate how rate effects influence the slow-to-fast tr...
Slope stability in reservoirs depends on time-dependent triggering factors such as fluctuations of the groundwater level and precipitation. This paper assesses the stability of reservoir slopes over time, accounting for the uncertainty of the shear strength and hydraulic parameters. An intelligent surrogate model has been developed to reduce the co...
The New Austrian Tunnelling Method (NATM) tunnel design is performed by testing support classes against the geological profile. We propose to replace this manual process with reinforcement learning, a generic framework within the realm of artificial intelligence that solves control tasks.
Previous studies have demonstrated this possibility, albeit...
A thermodynamically consistent phase field model with new crack driving forces is proposed to simulate the mixed-mode fracture phenomena in rock-like materials. The governing equations are derived using the volumetric and deviatoric strain split. Based on the Benzeggagh–Kenane failure criterion, our model captures the salient features of different...
Most deep-seated landslides are characterized by large volumes with deep shear surfaces. They are sensitive to hydrological forcing, especially in climate change scenarios. This paper studies the role of soil–water interaction in affecting the motion of a deep-seated landslide near the southeast coast of China, where seasonal rainfall combined with...
The three-halves Bagnold profile for granular flow down an incline, assuming no-slip at the base, is a generally accepted velocity profile that applies in many instances. In the intermediate dense regime, the material behaviour resembles a Bingham fluid and the widely accepted friction model - μ(I) rheology originally defined within the realms of v...
Chong Peng Shuai li Wei Wu- [...]
Hui Tang
Lagrangian particle-based smoothed particle hydrodynamics (SPH) is increasingly widely used in landslide modelling. This paper investigates four important issues not addressed by previous studies on SPH modelling of large-scale landslides, i.e., convergence property, influence of constitutive parameters, scale effect and friction reduction, and inf...
This is a poster for the annual department meeting of the Department of Civil Engineering and Natural Hazards at BOKU. Please feel free to request the LaTex poster template.
This paper presents the results of centrifuge tests on rainfall-induced instabilities in variably saturated slopes. The roles of rainfall intensity and initial conditions, such as slope angle, porosity and degree of saturation of the soil, in the failure initiation and postfailure kinematics are considered. The failure patterns, infiltration profil...
In this paper, a new Lagrangian differencing dynamics (LDD) method is presented for the simulation of granular flows. LDD is a truly meshless method, which employs second-order consistent spatial operators derived from the Taylor expansion and point renormalization. A decoupled pressure-velocity formulation is employed to derive the pressure Poisso...
Cone penetration test (CPT) is widely used to explore the in situ soil mechanical properties and the stratigraphy. The numerical simulation of CPT can help understand its mechanical process and link the testing data to soil properties. However, this task is challenging due to multiple (i.e., geometric, material and contact) nonlinearity of the prob...
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...
The study on fluid-solid interaction in heterogeneous suspensions is essential for theoretical research and engineering practice. In this paper, a three-dimensional fully resolved SPH-DEM method is presented to model suspen-sions with non-Newtonian fluids and solid particles of arbitrary shape. The fluid phase is modelled using SPH with a regulariz...
Clastic soil is ubiquitous in practice but still poses challenges for testing and modelling. Conventional laboratory tests with small sizes are not suitable for the large grain size, while large-scale tests and field tests are often too costly and time-consuming. In this paper, the mechanical behaviour of clastic soil is described by a hypoplastic...
Frequent water level fluctuation such as wave is one of the significant differences that distinguish subsea tunnels from land tunnels. For a better understanding of the influence of the dynamic wave loading, this study develops a new set of analytical solutions for the wave-induced hydraulic response on the subsea shield tunnels. The proposed analy...
In this paper we exploit the fact that dense granular flow down an inclined chute exhibits a simple scaling property. This implies that the fundamental governing partial differential equation admits similarity profiles which are applicable to any general friction law \(\mu (I)\) of the material irrespective of the particular functional form under c...
A non-orthogonal elastoplastic constitutive model for sand with dilatancy is presented in the characteristic stress space. Dilatancy of sand is represented by the direction of plastic flow, which can be directly determined by applying the non-orthogonal plastic flow rule to an improved elliptic yield function. A new hardening parameter is developed t...
A non-orthogonal elastoplastic model for clay is proposed by combining the non-orthogonal plastic flow rule with the critical state concept, and the model framework is presented from the perspective of the magnitude and direction of the plastic strain increment. The magnitude is obtained based on the improved elliptical yield function and the plast...
Clastic soil is ubiquitous in practice but still poses a challenge for testing and modelling. Conventional laboratory tests with small sizes are not suitable for the large grain size, while large-scale tests and field tests are often too costly and time-consuming. In this paper, the mechanical behaviour of clastic soil is described by a hypoplastic...
Most granular materials encountered in nature and industry lie either in the quasi-static regime or the intermediate dense flow regime. Debris materials are a typical granular material with viscous interstitial fluid, and shows solid-like behaviors before failure and fluid-like behaviors after failure. Based on Bagnold’s pioneering work on granular...
The mechanical behaviors of methane hydrate-bearing sands (MHBS) are largely affected by the presence of methane hydrate, temperature, and pore pressure. In this study, we present a simple hypoplastic model for MHBS. Methane hydrate saturation is included as a state parameter affecting the mechanical behaviors of MHBS. A new phase parameter is intr...
This paper presents a new rate-dependent hypoplastic constitutive model for overconsolidated clays. The model is developed based on a basic hypoplastic model proposed recently for sand. New density and stiffness factors are introduced to account for history dependence. The Matsuoka-Nakai failure surface is incorporated for the limit stress criterio...
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 ba?es. Hence, the estimation of impact force of debris flow is crucial for designing step-pools channel. Existing empirical models for impact pressure prediction cannot consider the influence...
A surface mesh represented discrete element method (SMR-DEM) for granular systems with arbitrarily shaped particles is presented. The particle surfaces are approximated using contact nodes obtained from surface mesh. A hybrid contact method which combines the benefits of the sphere-to-sphere and shpere-to-surface approaches is proposed for contact...
Particle finite element method (PFEM) is an effective numerical tool for solving large-deformation problems in geomechanics. By incorporating the node integration technique with strain smoothing into the PFEM, we proposed the smoothed particle ?nite element method (SPFEM). This paper extends the SPFEM to three-dimensional cases and presents a SPFEM...
Most slow-moving landslides in the Three Gorges Reservoir (TGR) region of China are characterized by pre-existing shear surfaces. The large deformation within the shear zones usually gives rise to clastic soil formation. The creep properties have large influence on the kinematic feature of landslides. In this paper, we report an in-situ direct shea...
Most granular materials encountered in nature and industry lie either in the quasi-static regime or the intermediate dense flow regime. Debris materials are a typical granular material with viscous interstitial fluid and show solid-like behaviors before failure and fluid-like behaviors after failure. Based on Bagnold’s pioneering work on granular–f...
Poster EGU2014
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 capabl...
The mechanical behaviors of methane hydrate-bearing sands (MHBS) are largely affected by the presence of methane hydrate, temperature, and pore pressure. In this study, we present a simple hypoplastic model for MHBS. Methane hydrate saturation is included as a state parameter affecting the mechanical behaviors of MHBS. A new phase parameter is intr...
Particle finite element method (PFEM) is an effective numerical tool for solving large-deformation problems in geomechanics. By incorporating the node integration technique with strain smoothing into the PFEM, we proposed the smoothed particle finite element method (SPFEM). This paper extends the SPFEM to three-dimensional cases and presents a SPFE...
Hypoplastic constitutive models are able to describe history dependence using a single nonlinear tensorial function with a set of parameters. A hypoplastic model including a structure tensor for consolidation history was introduced in our previous paper (Wang and Wu in Acta Geotechnica, 2020, https://doi.org/10.1007/s11440-020-01000-z). The present...
Infrastructure are long-lasting products which have huge impacts on the environment during their whole lives. The design and subsequent maintenance of infrastructure should take into consideration long-term environmental and economic benefits. Through a systematic literature review this report presents the concept of sustainable infrastructure desi...
Predicting the onset of shear band is of significance in understanding the failure of geomaterials. The prediction accuracy is dictated by the constitutive model used for the description of the pre-bifurcation behaviour. In this study, we first modify a recently proposed hypoplastic constitutive model by incorporating a general strength criterion a...
This paper presents an experimental investigation on the loading-relaxation behaviours of reconstituted shear-zone soils through drained triaxial tests. A multistage loading-relaxation approach is adopted to perform this test. The test aims to study two main issues: the influence of relaxation on the mechanical response during reloading, and the in...
This paper presents an experimental investigation on the loading-relaxation behaviours of reconstituted shear-zone soils through drained triaxial tests. A multistage loading-relaxation approach is adopted to perform this test. The test aims to study two main issues: the influence of relaxation on the mechanical response during reloading, and the in...
A surface mesh represented discrete element method (SMR-DEM) for granular systems with arbitrarily shaped particles is presented. The particle surfaces are approximated using contact nodes obtained from surface mesh. A hybrid contact method which combines the benefits of the sphere-to-sphere and sphere-to-surface approaches is proposed for contact...
Clastic soil is ubiquitous in practice but still poses challenge for testing and modelling. Conventional laboratory tests with small sizes are not suitable for the large grain size, while large-scale tests and field tests are often too costly and time-consuming. In this paper, the mechanical behaviour of clastic soil is described by a hypoplastic c...
Unlike the existing truss models for shear and torsion analysis, in this study, the torsional capacities of reinforced concrete (RC) members were estimated by introducing multi-potential capacity criteria that considered the aggregate interlock, concrete crushing, and spalling of concrete cover. The smeared truss model based on the fixed-angle theo...
The thermomechanical behaviour of soils is significantly important in some geoengineering applications, such as design and installation of energy piles,radioactive waste disposal, burying of high-voltage cables and geothermal pipelines in soils, among others. These applications have led to the increased interest of the temperature effects on the en...