A1 – Hazard departure
The frequency of impact results from the frequency of failure, currently rated qualitatively, and from the probability of propagation. The objective is to quantify the frequency of rupture, which will make possible the quantitative assessment of the frequency of impact and risk. The influence of meteorological factors on the incidence of rupture will be also studied, allowing the modeling of the influence of climate change.
Quantify frequency of departure for block based on the volume
Measurement on different type of cliffs (Lidar and Photogrammetry at different times) to give the altimeter in different contexts geological and meteorological
The proposed approach will allow a truly quantitative assessment of the risk of rupture and thus to hazard resulting (frequency of impact on an issue), and risk. To enable designers to use it, a classification of rock walls will allow to estimate the spatio-temporal frequency of landslide (number of falls by century depending on volume) depending on the geological characteristics and environment of the wall. A simple method to deduce the number and size of blocks to introduce in trajectography software to model the behaviour of a watershed for a certain period and deduce the impact frequency. This approach
Confrontation of different approaches of characterization of localized hazard (risk zone well identified and localized) on instrumented and well-documented reference sites
Instrumentation of sites, access to data and previous analyses, evaluation of hazard by different agencies (BE, research laboratory,…)
State of knowledge relative to the hazard of the Rocky escarpments and cliffs. Presentation of the results of the benchmark and proposal of a methodology.
Contribution to a discussion paper on the research work on the theme of the risk of failure in both cases.
Improved measurement methods for characterizing the localized hazard
Dynamic response to the seismic noise floor, photogrammetry with structural analysis software
A new approach for the assessment of the unstable Rocky compartments (or potentially unstable) will be proposed, based on a more realistic geomechanictic modeling, as compatible with the observed behaviour of the compartments in response to the seismic noise floor, and taking into account the maximum available information surface with photogrammetry.
The geomechanical modelling will assess the stability of the Rocky compartments (which depends strongly on the persistence of discontinuities), to interpret their evolution where a temporal evolution is observed (the measure of the seismic noise supplementing traditional monitoring by extensometry) and size reinforcement if necessary. The effectiveness of strengthening in terms of stiffening of the wall, can be controlled by new seismic measurements and checking that resonant frequencies have increased after strengthening. This method of control is easy to perform, could prove more economical than anchors pullout tests.
A simplified evaluation method (charts), will be proposed to establish a preliminary rapid diagnosis of potentially unstable rock compartments from seismic measurements, without resorting to a finite element calculation.
A2 – Sensitivity of hazard trigger uncertainties and climate change
The climate context of the rock plays an incontestable role in triggering the movement of boulders. Factors characteristic of the massif and materials on the one hand, environmental factors on the other hand are the two sets of parameters that influence the occurrence of hazard “fall of boulders”. This action will focus on two families, with a special effort on climate data modeling, and rely on data obtained within other actions for the characterization of the parameters of the massif. It will operate in particular feedback data from observation of the massifs (monitoring environmental, followed by deformations, statistical fall…).
In a context of climate change, it should be:
- clarify values and ranges of variations of the most influential environmental factors,
- specify the weight of these factors by a detailed analysis of the trigger mechanisms,
- on the basis of the experience feedback, quantify relationships between environmental variables and the descriptive parameters of induction,
- estimate how the tripping hazard is likely to evolve to specific climate change scenarios.
Definition of environmental parameters that can be used in models of trigger (risk of departure)
Analysis of instrumented full-scale sites, laboratory testing, modelling hydro-thermo-mechanical analysis
Better knowledge of climate-induced mechanisms influencing the block falls, especially in what concerns the phenomena of thermal cycling.
Combination of the problems of spatial variability (features hydro – and geomechanical across the massif) and temporal variability of the climatic characteristics to implement an approach to develop term mapping of hazard in terms of return period, adapted to a dynamic development to integrate the effects of climate change.
The statistico-reliability analysis of the outbreak will also target efforts to better reduce the uncertainties on the FTAA: we should first learn the massif and its variability, should be better clarify the expected climate changes, should develop more accurate models for prediction of hazard?
Research of correlation between extreme events and climate change
Statistical databases of landslides and weather analysis (collaboration with weather France)
It is expected from this action of strong fundamental opportunities concerning the link between rare blocks falls and changes in climate.
Term, significant operational benefits are likely in terms of improvement of trajectographiques codes, including the point of view of events sizing to the zoning by-law (the strongest) and taking account of non-climate stationnarites in their assessment.
A3 – Risk of spread
This action consists of laboratory and field testing in order to achieve a benchmark of different approaches to modeling in trajectographique analysis.
Confrontation of different approaches to characterisation of hazard spread
Testing of releases of blocks in controlled on two instrumented sites conditions. Comparison of the results of the modeling benchmark measures
Benchmark on the basis of tests on a reduced scale
Comparative analysis of the relevance of the different types of models (point models, models taking into account explicitly the form,…), to translate the physics governing the spread of boulders and the variability of this phenomenon.
Benchmark on the basis of releases free trajectories on live site.
Two objectives are covered through this benchmark:
- the possibility for users and developers of codes to improve their tools and practices,
- be able to assess the level of trust that may be given to the simulation results (plaintext, for example: ‘given current resources, an uncertainty of X % can be applied to values of passage height from trajectographique simulations’).
A3.2 - Taking into account variability and uncertainty of field parameters on the evaluation of spreading hazard
Quantifying uncertainty on the characterization of the risk of spread by estimate and propagation of the uncertainties and variability of trajectographique modelling parameters
Methodological developments. Applications on pilot sites
Improve the taking into account of the forest cover in trajectographique analysis
Laboratory testing, testing of calibration in the field, models of interaction between blocks and trees
This research action will lead to define a protocol of integration of a module for taking account of the forest in trajectografic analyses of different types software.
Furthermore, the model developed will allow to quantify accurately the effect of forest on the spread of the blocks. The findings of this study will be exposed in the working groups on the quantification and zoning of the risk of spread and incorporated into the guides or methodological recommendations on these topics.
Dispose of first low volumes landslides (rock avalanche) modeling tools, less than 1,000 m3.
Use of model test results reduces to calibrate a digital model. Extrapolation to real websites.
- better knowledge of the mechanisms of spread of rock avalanches.
- improvement and validation of the calculation methods
- establishment of a database of the calculation parameters
- transfer to operational
- development of a methodology of calculation specific to each code used.
Test a method for measuring the hazard resulting in an infrastructure copyright
Listen for seismic action
- Knowledge of the measured and quantified hazard for 2 different configurations.
- Discrimination of the signals of blocks falls. Today, it is not known how to discriminate reliably dropping block from an analysis in the time field, frequency field or time frequency of a seismic signal.
- Temporal localisation of blocks falls. Today, because of the great heterogeneity of soil and therefore physical parameters (speed, density, etc.) the classical techniques of event location are not exploitable.