SafeLand FP7 Deliverable Archive – Hydromechanical Modelling Guidelines
Deliverable D1.4 of the SafeLand FP7 project provides structured guidelines for selecting and applying numerical simulation codes for predicting climate-induced landslides.
The document was coordinated by the École Polytechnique Fédérale de Lausanne (EPFL) and synthesizes the geomechanical mechanisms introduced in D1.2 into practical modelling workflows.
Main Objective
D1.4 aims to evaluate slope-scale and regional-scale numerical tools used for rainfall- and snowmelt-driven instability assessment. It provides procedures for preprocessing, transient hydrological–mechanical analysis, and post-processing interpretation.
The goal is to ensure that model complexity aligns with hazard assessment and Quantitative Risk Assessment (QRA) requirements.
Climate-Induced Triggering Mechanisms
Shallow Landslides
- Rainfall infiltration reduces matric suction
- Collapse or static liquefaction in granular or collapsible soils
- Rapid pore pressure rise near slope surface
Deep-Seated Instability
- Groundwater seasonal fluctuations
- Progressive shear failure along weak interfaces
- Viscous or creep-like deformation
Coupled hydromechanical (HM) processes are emphasised, where pore pressure changes directly influence stress distribution and deformation.
Physical and Numerical Framework
Hydrological Modelling
- Richards equation for unsaturated flow
- Darcy flow for saturated conditions
- Soil water retention curves (SWRC)
- Hydraulic conductivity anisotropy
Mechanical Modelling
- Elasto-plastic constitutive behaviour
- Non-associative flow rules
- Dilatancy and wetting collapse
- Shear Strength Reduction Method (SSRM) for Factor of Safety
Evaluated Numerical Codes
Slope-Scale Finite Element / Finite Difference Codes
- Lagamine
- ZSoil
- PLAXIS
- FLAC
These allow coupled hydromechanical modelling, unsaturated soil mechanics, and transient stability simulations.
Regional GIS-Based Codes
- SHALSTAB
- TRIGRS
- I-MOD3D
These apply infinite slope assumptions combined with infiltration modelling to produce basin-scale susceptibility maps.
Modelling Workflow Guidelines
1. Geological Model Definition
- Layering and stratigraphy
- Hydraulic anisotropy
- Fractures and heterogeneities
2. Input Parameter Collection
- Shear strength parameters from laboratory testing
- Hydraulic conductivity from field tests
- Soil water retention data from monitoring (e.g., tensiometers, TDR)
3. Preprocessing
- Initial stress state (K0 conditions)
- Mesh discretization strategy
- Assignment of boundary conditions
4. Analysis
- Transient rainfall or snowmelt loading
- Coupled HM computation
- Shear strength reduction for stability evaluation
5. Post-Processing and Validation
- Plastic strain localization patterns
- Shear zone identification
- Comparison with field displacement data (inclinometers, DIC)
Applications and Case Studies
The modelling procedures were validated against European case studies including Alpine slopes such as Super-Sauze and Italian pyroclastic terrains affected by intense rainfall events.
Benchmarking exercises (e.g., Sarno 1998 rainfall-induced landslides) demonstrate the strengths and limitations of regional infiltration models.
Practical Implications
- Improved hazard zoning and susceptibility mapping
- Early Warning System (EWS) threshold calibration
- Prediction of failure timing under extreme rainfall
- Scenario analysis for climate change projections
The deliverable emphasises iterative modelling: simulation → monitoring validation → parameter refinement.
Technical Keywords
- Hydromechanical coupling
- Richards equation
- Soil water retention curve
- Shear strength reduction
- Infinite slope modelling
- Unsaturated flow mechanics
- Progressive failure analysis
- Transient slope stability
- Early warning systems
- Constitutive soil models (BBM)
Role Within the SafeLand Research Framework
D1.4 operationalizes the physical mechanisms defined in D1.2 and supports the model selection recommendations later formalized in D1.8 for Quantitative Risk Assessment.
It bridges theoretical soil mechanics and applied hazard forecasting within European mountain and volcanic environments.