TRIGGERering mechanismsof LANDslides : analysis and modelling – TRIGGERLAND

Scientific background and objectives – Landslides monitoring, modelling and forecasting is a rapidly
advancing research field. There are many new techniques being developed, as well as challenges of data
acquisition and analysis. Despite considerable advances in the last decade, there are still gaps which must be
filled, in order to apply this knowledge for the long-term development of mountain territories and for the safety of
citizens. This is mainly the consequence of the large kinematic variability of gravitational phenomena, of the
control of many static terrain conditions (rock, soil) and preparatory factors, of the existence of several triggering
mechanisms, of their transient and non-linear behaviour, and of the lack of accurate landslide models.
Therefore, the main objective of this project is to deliver new technologies (experimental prototypes, numerical
tools, models) in order to better understand the processes governing landslide failures and particularly to
identify landslide patterns and possible forerunners that characterize significant changes in landslide dynamics.
Many laboratory and field data from instrumented sites are available on many aspects of landslide dynamics
(landslide databases and event catalogues, multi-parameter monitoring datasets, detailed geomorphological,
geotechnical and geophysical concepts), but we are still lacking analytical and numerical analysis tools because
of landslide complexity and dependence of the controlling parameters. Moreover, many studies have focused
on the post-failure stage of landslide (e.g. slow or fast propagation, rock avalanches, debris flows); few studies
were performed on the pre-failure and failure stages of landslides which understanding is of paramount
importance for hazard assessment (estimation of the volume able to fail, estimation of the rheological and
kinematic characteristics of the failed material) and for early-warning or threshold identification (time to failure).
Description of project and methodology – Three Working Blocks (WB), related to the 'life' of an unstable
hillslope (e.g. landslide), from the preparatory stage to the triggering stage and finally failure, have been
defined. These WBs are characterized by several specific research actions:
WB-1: To improve our understanding of the preparatory factors controlling long-term slope behaviour and
mechanisms (pre-failure stage).
WB-2: To improve our understanding of the triggering factors controlling landslide failures or landslide crises
as accelerations (failure stage).
WB-3: To progress in the predictable time scale of landslides and identify elements for early-warning planning
through detailed field case analysis introduce standardised procedures for landslide hazard.
The project will make extensive use of experimental analysis in the laboratory (flume tests, torsion and triaxial
tests, creep tests), development of physically-based numerical models, and analysis of monitoring datasets.
The developed technologies will be applied to largely documented case studies, in order to quantify their
reliability and applicability. All tasks have strong connections with work carried out recently by the partners,
which significantly increases the feasibility of the project.
The originality of this project is to propose a global approach for both hard rocks and soft rocks (e.g. soils)
instabilities. This approach has already proven to be very successful within the SAMOA Project which has been
supported by the French Ministry of Research through the ACI 'Prévention des Catastrophes Naturelles' (2002-
2004). This will allow us to collectivise the experimental and numerical knowledges which are generally
developed separately and to benefit from complementary technologies and prototypes. The association of
researcher coming from various scientific fields and having already experienced such a pulridisciplinary
collaboration, should be particularly fruitful. This is aimed to improve widely the applicability of numerical and
experimental approaches on landslides, particularly in the case of complex landslides, for which the behaviour
can be a combination of rock/soil/fluid behaviour and can switch from one to the other.
The project is proposed for a duration of 4 years in order to monitor field records of substantial length to detect a
wide range of meteorological, piezometric and earthquake conditions that may trigger instability on the sites. As
the ultimate goals of the project are to develop analysis prototypes and modelling tools, we have chosen to
dedicate the major part of the budget to the recruitment of 6 post-docs (with contracts of 1 year).
Added value of the cooperation – The strength and the originality of this project will be to combine different
techniques and methodologies and to join the capabilities and competences of various expertises within a
coordinated approach (geomechanics, geophysics, geomorphology, engineering geology, hydrology and
hydrogeochemistry). The multidisciplinary background of the members could potentially lead to the development
of new concepts and emerging strategies for landslide hazard analysis. Moreover, the project consortium
integrates two foreign research groups (Utrecht University – Faculty of Geosciences; Politecnico di Torino -
Dipartimento di Ingegneria Strutturale e Geotecnica) to widen its global expertise; the role of these foreign
groups will also to host for a short period of work the hired post-docs.