Multiscale and probabilistic modelling of progressive slope failure

Lead Research Organisation: Brunel University London
Department Name: Civil and Environmental Engineering

Abstract

In the UK and globally, the slope failures of various sizes are crucially affecting the sustainable development of resilient cities, as its occurrence can significantly threaten the populations, infrastructures, public services, and environment. For example, the British Geological Survey has estimated that 10% of slopes in the UK are classified as at moderate to significant landslide risk, with more than 7% of the main transport networks located in these areas. These slopes may fail during prolonged periods of wet weather or more intensive short duration rainfall events.

To date, the public awareness of slope failure risk is high, but our understanding of its fundamental failure mechanism and countermeasures are still very limited. This is mainly due to the difficulties in analysing the multiscale responses and characterize the spatial inhomogeneity of material properties of slopes. Laboratory and numerical investigations with well-developed empirical models can explain the general features of some specific slope failure events but cannot be applied universally. Some challenging issues need to be addressed, such as i) How to develop reliable mathematical models with multiscale modelling capability to analyse the progressive failure of slopes? ii) How to address the spatial variabilities and uncertainties of real slopes, e.g. material property, fractures, fluid permeability? iii) How to accurately estimate the spreading of landslide and its impact on infrastructures? The fundamental scientific issue of these challenges is the weakening mechanism of inhomogeneous slopes at different scales as it determines the slope responses under various geological and environmental conditions.

The proposed research aims to explore the fundamental mechanism of progressive slope failure and its impacts on infrastructures via a multiscale and probabilistic modelling approach. It enables the large deformation of slopes to be conveniently analysed by FEM as boundary value problem (BVP), while the local fracturing, cracking, or discontinuous behaviours of soil to be evaluated in smaller discrete subdomains through granular mechanics by DEM. The boundary condition of DEM assembly is derived from the global deformation of FEM meshes. In the analysis, the soil/rock properties (e.g. elastic modulus, friction coefficient, strength, and fluid permeability) will be evaluated as random fields with spatial variabilities. The numerical modelling can effectively bridge the gap between the microscopic material properties and the overall macroscopic slope responses. In the numerical modelling, the contributions of material inhomogeneity and discontinuity to slope failure and subsequence landslide spreading can be effectively investigated. The internal fracture would occur naturally when the loading stress exceeds the particle bonding strength at the microscale, which avoids the use of some phenomenological constitutive laws in conventional continuum modelling.

As a multidisciplinary research, this project will involve the subjects of geotechnical engineering, computational geotechnics, geology, statistics, soil/rock mechanics and granular mechanics. The proposed numerical model will benefit all researchers and stakeholders in land planning and management by providing efficient and reliable numerical modelling approaches. This will support the landslide risk evaluation, hazard mitigation and long-term land management, from which the environmental, social, and economic benefits can be achieved. As a result, the decision makers would have greater confidence in slope failure risk assessments on which they are basing their infrastructure investment considerations. Consequently, hazard warning systems, protections and land utilization regulations can be implemented, so that the loss of lives and properties can be minimized without investing in long-term, costly projects of ground stabilization.

Publications

10 25 50
 
Description The research team has successfully programmed the random field theory model in the well-developed continuous-discontinuous modelling platform. This multiscale and probabilistic modelling approach has been employed in investigating the progressive failure of slopes, the impact of cliff collapse on key infrastructures (e.g. road, railway). The numerical results could effectively guide the design of new infrastructure and protect the existing ones.
Exploitation Route The research team is exploring opportunities to work with some UK coast management groups to apply the research outcomes in real landslide hazards.
Sectors Construction

Transport

 
Description Postdoctoral Fellowship (Dr. Bin Gong)
Amount € 236,748 (EUR)
Organisation Marie Sklodowska-Curie Actions 
Sector Charity/Non Profit
Country Global
Start 11/2023 
End 10/2025
 
Title The coupled discrete element method (DEM) - random field theory (RFT) model 
Description The RFT-DEM model has been further improved in this work to simulate the mechanical behaviour of rocky cliffs under the earthquake loading. In this method, the material properties are considered as a series of random values generated at discrete particle centres, following the standard Gaussian distribution pattern. These random values are mutually correlated by a specified correlation length (i.e. scale of fluctuation) using the modified linear estimation method. The properties of adjacent soil particles as variables within this length scale do not differ too much as those further apart. The generation of random fields is repeated for a huge number of times with distinctly different random values in each run. Once the random fields are generated, they are imported into DEM for modelling the earthquake induced slope fracturing. 
Type Of Material Improvements to research infrastructure 
Year Produced 2021 
Provided To Others? Yes  
Impact Many geotechnical researchers have employed this method in their research. 
URL https://figshare.com/s/bdc2051f08d477988bba
 
Title The coupled finite element method (FEM) - discrete element method (DEM) model 
Description The coupled FEM-DEM model has been developed to characterize the cross-scale failure process of discontinuous rock mass involving the fine fracture creation, propagation and penetration based on the rock mechanics, computational geomechanics and contact theory. For the developed FEM-DEM model, by deducing the unified global equilibrium equation, the continuous and discontinuous problems can be solved jointly, i.e., the mechanical behaviors of continuous regions and discontinuous structural planes can be simulated simultaneously; by constructing the specific fracture sequence to connect continuous medium with discontinuous medium, the automatic transformation of rock materials from continuous medium to discontinuous medium can be realized; by establishing the unified analytical framework, the cracking process of rocks at small deformation stage and the movement and contact process of blocks at large displacement stage can be fully captured, and the whole-process simulation of rock failure and instability can be achieved. 
Type Of Material Improvements to research infrastructure 
Year Produced 2023 
Provided To Others? No  
Impact The developed FEM-DEM model can provide an entire and unified description for rock deformation, crack initiation and growth as well as rock body translation, rotation and mechanical contact, and can effectively reproduce the progressive process of landslides. 
 
Title The improvement of the commercial software Plaxis to couple Random Field Theory 
Description The developed tool has coupled the traditional FEM model with the Random field theory to consider the heterogeneity of soil material properties. 
Type Of Material Improvements to research infrastructure 
Year Produced 2023 
Provided To Others? No  
Impact The coupled FEM-RFT model can be easily applied to the industrial designs. The company GDG has express great interest in this work. 
 
Title Analysis of Rainfall-Induced Slope Stability using Probabilistic and FEM Hydro-Mechanical Coupling 
Description In this research, an integrated approach combining random fields and FEM hydro-mechanical coupling was employed to investigate the occurrence of shallow landslides near the slope surface during and after rainfall events. The related Python script to generate random fields and Plaxis input codes are included. 
Type Of Material Database/Collection of data 
Year Produced 2023 
Provided To Others? Yes  
Impact The Plaxis model can be used to guide the slope design. 
URL https://brunel.figshare.com/articles/dataset/Analysis_of_Rainfall-Induced_Slope_Stability_using_Prob...
 
Title DEM-RFT model 
Description he coupled discrete element method (DEM) - random field theory (RFT) model has been developed to study the material heterogeneity in the microscale. The codes covers the generation of random fields and the DEM modelling of slope failure. 
Type Of Material Computer model/algorithm 
Year Produced 2021 
Provided To Others? Yes  
Impact The datasets includes detailed guidance on how to generate random fields and import them into DEM models. 
URL https://figshare.com/s/bdc2051f08d477988bba?file=31316530
 
Description Collaboration with Dr. Charlotte Thompson at University of Southampton 
Organisation University of Southampton
Country United Kingdom 
Sector Academic/University 
PI Contribution The team has regular meetings with Dr. Thompson for investigating the monitoring data of the coastal cliffs in the UK managed by her to clarify the long-term deformation trend and possible failure modes.
Collaborator Contribution Dr. Thompson has provided the monitoring data of the coastal cliffs in the UK managed by her as the director of the Channel Coastal Observatory. Meanwhile, Dr. Thompson has contributed to win the 2023 MSCA postdoctoral fellowship for Dr. Bin Gong.
Impact No
Start Year 2022
 
Description Collaboration with Dr. Indrasenan Thusyanthan at Gavin & Doherty Geosolutions (GDG) 
Organisation Gavin & Doherty Geosolutions
Country Ireland 
Sector Private 
PI Contribution The team has worked closely with Dr. Thusyanthan on developing advanced computational geotechnics models. Dr. Zhao, Dr. Thusyanthan and Dr. Gong have regular research meetings on landslide hazard studies, forming strong research collaborations.
Collaborator Contribution Dr. Thusyanthan has joined the research advisory board and help steer this research. He has guided the software development.
Impact The outcomes are not available.
Start Year 2021
 
Description Collaboration with Prof. Giovanni Crosta at University of Milano-Bicocca 
Organisation University of Milano-Bicocca
Country Italy 
Sector Academic/University 
PI Contribution The team has programmed the coupled FEM-DEM method and is applying it to model the field investigations conducted by Prof. Giovanni to clarify the mechanism of the observed slope failures.
Collaborator Contribution Prof. Giovanni has guided the software development and its application in understanding the progressive failure of actual slopes.
Impact The outcomes are currently not available because the relevant research is ongoing.
Start Year 2021
 
Description Collaboration with Prof. Gordon Zhou at Institute of Mountain Hazards and Environment, Chinese Academy of Sciences 
Organisation Institute of Mountain Hazards and Environment
Country China 
Sector Charity/Non Profit 
PI Contribution Dr. Gong had two meetings (on Jan. 11 and Feb. 26, 2023) with Prof. Zhou and his team in person at the Institute of Mountain Hazards and Environment, Chengdu, China. During the meetings, they discussed the application of the developed FEM-DEM method in clarifying the failure mechanism of the rockfalls monitored by Prof. Zhou.
Collaborator Contribution Prof. Zhou has provided guidance on modelling the failure mechanism of the rockfalls observed in Tibet, China.
Impact No
Start Year 2021