The National Monitoring Center for Ground and Underground Risks of Ineris, located at the School of Mines of Nancy, France, carries out research, expertise and early warning capabilities applied to field observation, monitoring and alert services related to ground and underground risks.
The CENARIS aims to develop, in the frame of both scientific and operational projects, innovative tools, methods and resources enabling to improve our understanding of physical processes linked to instabilities and disasters, to enhance forecasting capabilities as well as expertise applied to risk management.
- mines, quarries, and cavities,
- rockfalls, landslides and faults,
- structural engineering, dams and embankments,
- geological storage, rock reservoirs.
Cloud monitoring solutions, based on the e.CENARIS platform, are designed and implemented thanks to an extensive experience, providing optimally customized multi-parameter early warning systems. These include microseismic and advanced GPS-RTK geodetic measurement capabilities and feature a unique advanced website interface.
« Cloud Monitoring » presents a universe of tools, integrated and dematerialized services, which make project monitoring and information exchange for its members very simple.
The concept covers hazard and risk expertise, technical conception and feasibility of the project, observations and surveillance deployment systems. These cover: architecture and data acquisition, transmission, follow-up, control and data expertise.
Furthermore, Ineris conceives maintenance, vigilance and warning procedures, led consular crisis management exercises, and assures continuous feedback collaboration with the lead risk manager.
What is the « Cloud Monitoring » purpose?
As an integrated platform of observing and warning (fast and early) systems, data availability and accessibility are the main purpose of Cloud Monitoring. These are recognized as an efficient approach to highly reduce the population’s and property’s vulnerability, as well as improving its reactivity and resilience to hazards. The ability to operate global-scale geological and geotechnical surveillance, prevention and management solutions, constitute a major scientific and technical challenge in a generally complex context (with respect to anthropogenic activity, extreme climatic events effects, etc.).
What are the benefits of the e.cenaris platform?
The e.cenaris platform offers a high level of acquisition tools, management, data analysis and exchange, enabling optimized solution conception for every project case study.
Multi-parameter telemetry systems (SYTGEM) directly connected to the database with high-speed internet,
An automatic management infrastructure of the multi-parameter database (near real-time) with data teleprocessing and analyzing software, as well as alarm management structures,
A secure web-monitoring site for easy and fast access to data, metadata and associated results, with sharing conveniences between the project’s stakeholders.
To whom does the « Cloud Monitoring » address?
The E.CENARIS platform is meant for all bodies and partner research laboratories, communities, manufacturers, infrastructure managers, engineering offices, as well as decentralized departments in charge of telemetry and surveillance projects, linked to surface and subsurface problems.
Multi-parameter monitoring consists in deploying a system which allows to measure with the best resolution possible relevant variables with various natures (seismic, microseismic, geotechnical, geodesic, hydrological, meteorological, etc.) in order to detect not only hazard occurrence (rupture, collapse, sliding) but also to predict it. This implies the measure of triggering factors, for example exceptional pluviometry, increase of the interstitial pressure in grounds, a strong seismic excitation, and warning signs such as intense microseismic activity or the appearance of large deformations.
The multi-parameter monitoring system is possible thanks to the considerable technological progress made over these past years, concerning:
New generation acquisition,
Technology and radio transmission network developments and wireless connection,
Increased computer processing power, constantly becoming cheaper.
Global supervision of risks covers hazards, and, if necessary, the most vulnerable material stakes which are bound to it. Stakes supervision – buildings, works, infrastructures, etc. – when possible, can considerably improve the evaluation and the management of a crisis and post-crisis situation.
Integration under e.cenaris of a new module for more reliable operational monitoring through the management of alarms.
e.cenaris is an e-Infrastructure under continuous development, dedicated to the scientific observation and the instrumental monitoring for geotechnical and geological risk hazards. It enables the automatic management of data acquired by a high variety of sensors installed in vulnerable areas. By clicking on « Monitoring » on the home page, experts and site managers can access the online database, visualize the data, and get information on the general working state of the network. Data are displayed as graphs, tables, maps or 3D views to ensure a quick and efficient checking, adjustable to monitoring requirements and to stakeholders’ needs.
Data treated by custom time-series processing routines make it possible to work in near real-time on new transformed variables, which are easier to exploit by filtering, weighted moving average, daily cumulated data, etc. e.cenaris can also integrate independent variables coming from external sensors or databases related to industrial (flow, pressure, blast load,…) or natural (pore pressure, pluviometry, …) forcing processes, which facilitate regression analysis.
Data fusion technologies and the definition of complex alarms have lately been implemented into the platform as advanced decision-support tools. The latter is based on combining transformed-variable alarms associated with Boolean operators. This high level of alarm design and management enables a more efficient control not only of network working state but also of computed parameters variability and their coherence level, to ensure more relevant and more reliable alarm settings (e.g. determining the correlation between forcing variables and incident occurrence).
Microseismic surveillance is a non-intrusive passive technique which consists in detecting and recording the seismic waves emitted during fracturing and cracking of a rock mass. The principle is identical to the one implemented in seismology, except that the scale is reduced by some order of magnitude (lower than 2). The processing, analysis and interpretation of the sequences of microseismic events, in terms of their spatiotemporal distribution, rupture mechanisms, released source energies and frequency contents, supply essential information for ground movement hazard management.
Especially, observation and microseismic monitoring find very numerous applications in the fields of natural and industrial risk prevention. It is particularly well developed in the contexts of mine exploitation and hydrocarbon reservoirs, extractive activities generating important stress constraint redistribution (i.e. microseismic activities), and it also finds numerous other applications, such as:
Natural risk prevention: underground cavities, rock and landslides, faults,
Geologic storage monitoring
Reservoir surveillance of fluid injections/extractions in deep drillings,
Civil engineering: dams, engineering works, tunnels,
Acoustic monitoring of an underground cavity is a passive technique used to detect and record the sounds (areal and aquatic pressure waves) emitted during a block fall or fracturing of the cavity roof or pillars. Easily implemented, this method requires favorable environment conditions for the diffusion of these acoustic waves. Usually, it is best adapted for large abandoned and quiet underground cavities. A microphone, correctly implanted inside the cavity, enables to survey over an area of several tens to hundreds of meters diameter, depending on the context. Acoustic monitoring is a pertinent complement to geotechnical surveys in the context of extensive, complex and abandoned underground cavities presenting the risk of evolving vertically towards the surface (i.e. localized collapse or subsidence).
The cost and benefits of this technique are particularly advantageous, and instrumentation is relatively safe considering that the sensors (microphones and/or hydrophones) are not emplaced directly in the zones of strongest deformation. In cases where the cavity is inaccessible, acoustic monitoring of the cavity is equally possible by means of bore drilling, whereby the sensors are inserted inside boreholes. Subsequent analyses and processing of data enable to discriminate between the parasitic acoustic signals and those triggered by the geotechnical deterioration.
Geodetic monitoring by GPS-RTK network supplies all the quantitative data necessary for the complete analysis of the displacement field. To obtain the best possible precisions, while keeping the most essential “real-time” aspect within the framework of an operational ground movement monitoring, the involved principle is the real-time differential GPS precise RTK (Real Time Kinematic) measure.
This principle is based on a referenced marker placed in a stable zone: all the variations in position registered by this marker are considered, by definition, as measurement errors (mainly due to the crossing of the atmosphere by the signal or to terrestrial tides). These variations can then be communicated by radio transmission, in real-time, with one or several measurement markers in the hazard zone, and thus, can be affected by the same measurement errors that allow to drastically reduce the measurement uncertainties.
Furthermore, the RTK method, based on the comparison of the signal phases and not on its binary code, allows to measure much more precisely and also faster. It is then possible to obtain at least a centimetric (differential) precision, even with short measurement cycles (typically from 5 to 30 minutes) and without any treatment in retrospect, which allows to run it in near real-time conditions for the ground movement hazard management.
Measured variations recorded at the referenced marker (i.e. in stable zone) are transmitted in corrected format to the measurement marker located in the zone experiencing ground motion.
Ineris has developed a platform dedicated to geotechnical tests and to the management of risks linked to the presence of cavities. This platform is located inside the former limestone cave of Saint Maximin (Oise, France), which was exploited using the room-and-pillar mining method.
This platform extends over ~3 hectares, it is situated between 10 and 20 m depth, with accesses available from the hillsides. Security conditions, access and equipment facilities are suitable for the performance of tests and training activities.
There Ineris carries out studies on the stability of underground engineering structures as well as on deformation and rupture mechanisms through rock complexes. Experiments are also led to tests in real conditions some tools and methods used for the risk management, such as wall stabilization, landfilling, or monitoring.
Download presentation leaflet: Underground platform for geotechnical tests and for the management of hazards linked to cavities
Or contact: email@example.com
Among the stakeholders the most likely to deal with risks management, local authorities are especially concerned by instabilities of underground cavities such as sinkhole, local and large-scale collapse phenomena. These ground instabilities may have a high impact on public safety, properties and environment. It is then necessary for the decision-makers, and in some cases in emergency situations, to find out solutions to ensure public safety and the protection of structures, property and assets.
Options to eliminate the risks generally rely on expensive time-consuming solutions (backfilling, expropriation). In some cases, using appropriate monitoring tools as an early warning system offers a standstill strategy of great help while entering into large projects with management and decision making are not compatible with fast response and public safety.
Strongly recognized with a long experience in the auscultation and monitoring of underground structures (mines, quarries, underground storage), Ineris has developed and implemented specific methods and tools that can be adapted to a wide range of situations at risks:
Typical instabilities of ancient subsurface cavities: sinkhole and localized collapses,
Instabilities of deep large cavities: large-scale subsidence or generalized collapses.
Ineris’s approach is based on well-known monitoring methods, ranging from visual inspection, geotechnical, acoustic, geodesic or even microseismic monitoring.
Such methods can be used independently or in combination, depending on the situation and issues. Ineris also owns a high-level monitoring infrastructure, which enables to manage monitoring data in a seamless way and in quasi real-time, and to administrate multi-parameter early warning systems.
Feasability analysis, design and construction of the monitoring solution,
Continuous monitoring for permanent networks,
Remote monitoring and data management, metrological and functioning control,
Data processing and analysis, interpretation and expertise,
Monitoring procedures, trainings on crisis situations.
Monitoring of active, abandoned or revamped underground quarries; e.g. the investigation of a limestone quarry converted into thermal baths, by means of automated convergence analysis
Monitoring of shallow or deep mine structures; e.g. the investigation of a salt mine subject to sudden collapse and situated close to inhabited areas, by means of acoustic, microseismic and geotechnical methods
Monitoring of a mine subsidence phenomenon due to the exploitation of the water stored inside the mine; e.g. the automatic monitoring by means of differential GPS technology
High experience in field investigations and monitoring of areas subjects to ground deformations,
About forty monitoring networks deployed in France and abroad,
Quality of our activities approved by our clients and partners (EDF, Andra, IRSN, collectivities…),
Experienced working team able to carry on monitoring and alert systems and ready to respond to the needs of stakeholders and risk managers (24/24 operational). All these services are achieved within the framework of the CENARIS (National Monitoring Center for Ground and Underground Risks).
To meet your needs of diagnosis and performance assessment of underground engineering structures and infrastructures, Ineris designs, develops and implements innovative, stand-alone or coupled, geotechnical (strain and stress monitoring, tilt, displacement) and geophysical methodologies (passive acoustics, active tomography) to help your decision-making. Since each project is characterized by its specific setting, it is necessary to customize the solution, including the execution and the tools on a case-by-case basis.
It is essential to analyze the monitoring data and their evolution with time in order to assess the correct response or not of the geostructure to quasi static or dynamic solicitations. Whenever necessary, a numerical model is used to optimize the layout of the sensors. Field data also enable to check the reliability of the prediction model, which estimates the structure response to the solicitations.
Feasibility analysis, design and definition of the best diagnosis method and of the monitoring planning (periodic, continuous),
Three-dimensional geomechanical and geophysical modeling, including hydro-thermo-mechanical quasi static and dynamic solicitation,
Installation, remote monitoring and data management,
Data monitoring and analysis, interpretation and results assessment.
Well-known capabilities for field experimentation and operational monitoring of underground operations, managed through an experienced working team able to carry on multi-disciplinary projects with fast response to stakeholders, i.e. industries, state agencies and local authorities. All these activities are achieved within the framework of the CENARIS (National Monitoring Center for Ground and Underground Risks).
Ineris offers in situ measurement solutions to investigate, and if necessary to monitor in near-to-real time the static or dynamic stress fields exerting in your geostructure (rock-bedded structures, underground cavity, dam, etc) in order to provide a deeper insight in its stability conditions.
Ineris develops methods and specific tools on purpose for your site and according to the operating conditions of your engineered structure. Ineris identifies and sizes the most adapted stress monitoring solution in order to optimize the analysis and the interpretation of the measurement data.
The stability criteria of a geostructure is based on the fact that the stresses and the pressures exerting inside it, at its interfaces or all around it remain below its strength, all over the life cycle of the geostructure. In some cases where the engineered structures have been designed on an innovative way or for old structures subject to alterations or unexpected solicitations, it may be necessary to characterize the pre-existing stresses in order to control the actual stability conditions. In situ stress measurements are usually an important input parameter to set up and to run numerical models in order to analyze and predict the stability conditions of complex structures.
An instrumental solution can be based on the use of total pressure cells, interstitial pressure sensors, flat jack cells, strain sensors, deformation gauges and hollow cells, clinometers, extensometers, or if necessary on a combination of these complementary methods. Ineris also developed its own solution under the SYTGEOstress® designation (ROck Stress Analysis System).
The tools that are used to analyze the measured stress fields amplitudes and orientations enable to have an accurate overview of the global stress field, including gradient and concentrations areas. The devices are designed for long-term purposes and generally set with auto-calibration and auto-diagnosis functions.
Mines and quarries, engineering structures, deep storage areas, rock masses…
Analysis of feasibility, conception and sizing of the stress monitoring application considering two-dimension, three-dimension, static and dynamic models and using a predictive approach by means of hydro-mechanical numerical modeling,
Field monitoring campaigns,
Continuous monitoring for permanent networks,
Remote monitoring and data management,
Data monitoring and analysis, interpretation and results assessment,
Consulting and assistance.
Ineris has developed its competences in situ and for operational monitoring of underground structures thanks to its experienced working team able to carry on monitoring and alert system operations and ready to respond to the concrete needs of operators, State entities, territorial collectivities and engineering structures managers. All these activities are achieved within the framework of the CENARIS (National Monitoring Center for Ground and Underground Risks).
More specifically, Ineris has carried out in situ stress monitoring operations for more than 25 years (overcoring, doorstopper, flat jack…) and realized such surveys in numerous geo-engineering structures (deep mines, underground structures, dams…).
Ineris, together with the BRGM and the Cerema, is participating in a study to improve the knowledge about the “wide-collapse” ground movement hazard of the cliff located below Bonifacio Citadel. The works are performed in the framework of a research agreement with the Departmental Division of the territories and the sea (DDTM) and under the auspices of the General Division for the prevention of risks (DGPR).firstname.lastname@example.org
Visited by more than one million people every year, Bonifacio Citadel is characterised by old and dense buildings located above a badly-eroded 20-m-corbelled section of the cliff. Hazard studies led by the Cerema until now have highlighted the necessity to perform complementary geotechnical monitoring for 18 months.
In addition to the expertise about rock fronts’ stability, Ineris partners focus their inputs on their competences in numerical modelling and on the solutions for geotechnical monitoring. In particular, e.Cenaris web-monitoring platform for the supervision of geological and geotechnical risks and the long-range terrestrial LiDAR are used for an accurate observation of the cliff and the management of the acquired data.
Ineris assists the Saline Cérébos company on the technical and administrative procedural aspects for the cessation of the exploitation of Urcuit salt underground cavities. A deep analysis of the context and field investigations led to the implementation of monitoring methods, whose objectives are to minimize the environmental hazards linked to the closure of the email@example.com
More precisely, Ineris is in charge of:
the water monitoring (temperature and conductivity), in order to make sure that the former exploitation site does not contaminate the surface aquifers located just out of the site. This monitoring is also performed to control any possible accidental brine leak within the environment, in case of cavities’ collapse;
the pressure monitoring of three hydraulically-connected cavities, in order to control the evolution of the risks areas where collapses might have consequences.
The monitoring system also integrates an alert procedure, which enables, first to make the site evacuated in case of sudden and repeated pressure variations (possible precursory indicators of collapse), and second to deploy solutions for the observation of any brine leak within the environment in case of collapse.
The monitoring project as well as all the transferred instrumental data are managed from e.cenaris platform; this to follow and to control the evolution of the site in a remote way.
A substantial synthesis research work was performed by Ineris in 2017 on post-mining seismicity recorded within the coal basin of Gardanne since the mining structures were flooded in 2008. This year, research works, including a PhD thesis, have been launched to apprehend the seismic driving forces better and assess the seismic hazard firstname.lastname@example.org
This thesis is co-directed by the laboratory Géoressources of the University of Lorraine and carried out in collaboration with the BRGM and the IPG Paris. It will be based on a multidisciplinary approach with the objective to integrate the hydrogeological behavior of the flooded mining structures together with the local tectonic context.
Acquired knowledge and results of this research work will be used by the scientific community and expert people responsible for the prevention of risks arising from the exploitation of underground resources and likely to generate instabilities and induced seismicity (mining exploitation, deep geothermal energy, CO2 geological confinement, waste storage…).
Post-mining seismicity recorded within the former coal basin of Gardanne between 2008 and 2014 (Matrullo et al. 2015)
The circles represent the location of the seismic events, their colors are related to the magnitude;
the blue line at the center of the basin corresponds to the waterfront limit in the mining structures;
squares and triangles represent the seismological stations;
the red zone represents the extension of the mine structure.
Road and urban developments sometimes face a risk of localized collapse due to the presence of karsts, old mines or marl quarries. The reinforcement of surface terrain by geosynthetics, is a solution to reduce the risk and allow these email@example.com
The objective of the REGIC project supported by the ADEME is to propose solutions for the design, manufacture and validation of "smart" geosynthetics integrating sensors for the monitoring of reinforced and remodeled terrains, in particular in terms of displacement, deformation and settlement.
This project focuses particularly on the application to road or urban structures, thin, supporting traffic loads, if any, and located in line with known or potential cavities, at shallow depths (about 1 m). In the case of existing cavities, the fragility of the cover poses the problem of compacting the overlying layers.
This project includes the realization in 2017 of an experiment in full size, on an old cavity (catiche) with the support of the city of Lille and the CEREMA. The implementation of the geosynthetic layer was carried out in a coherent and shallow soil. Various instrumentation and monitoring systems have also been installed to monitor the behavior of the catiche head, the surface soil and the geosynthetic. The results obtained will make it possible to improve the method of reinforcement dimensioning by a layer of geosynthetic.
Our partners : ADEME, Lille (France), CEREMA, TEXINOV, 3SR.
Ineris is a partner of the EPOS H2020 project, whose objective is to create an integrated, multidisciplinary and open European research infrastructure dedicated to earth firstname.lastname@example.org
Ineris is actively contributing to the theme of "anthropogenic hazards" in WP14, which aims to facilitate and stimulate research and synergies in fields related to the exploration and exploitation of geo-resources, as well as management of geo-risks.
In this framework, Ineris participates on the development of the TCS-AH platform (https://tcs.ah-epos.eu/login.html) and is mainly involved in:
the coordination of the working group responsible for evaluating and polishing the functioning of the e-platform, the quality of the information (data, services, documentation) and its valorization and dissemination through communication actions;
the provision of two documented databases, also known as "episodes", linked to the anthropogenic seismicity and resulting from partnership research projects. The first episode is emblematic of the mining and post-mining fields; The second concerns the study of saline gas storage cavities subjected to rapid exploitation cycles;
the contribution to the development of a hazard and multiple risk assessment tool for exploring and exploiting geo-resources with focus on deep drilling operation, being one of Ineris’s principal expertise.
The prototype of TCS-AH infrastructure is created and accessible online and will be shortly evaluated by the European Commission.
The research project DEMOSTHENE is funded by the French region of Hauts-de-France. It consists in designing and operating an experimental site of hot water storage in an abandoned mine. If it is conclusive, it aims at valorizing the many abandoned mines of this territory by realizing several heat energy seasonal email@example.com
The objective of this project is to operate an experimental pilot to estimate the energy efficiency of this type of storage and to identify the possible risks that thermal cycles may pose to the stability of underground voids.
The demonstrator is implemented in the Parrain’s limestone mine, located in Saint-Maximin (Oise, France), for a period of 12 to 24 months. It is based on a 120 m3 hot water basin, used to simulate the summer air conditioning then the winter heating of a 180 m² building that would be on surface. The experiment began in July 2017 and consists of filling the basin with water at 10 °C, warming it up to 80 °C over a period of 6 months and then cooling it over a similar period.
A multi-parameter instrumentation has been set up with 25 different probes. It includes the monitoring of (i) the warming and the cooling of the basin and its surrounding environment (air, backfill, rock), (ii) the quantification of the air masses exchanges between the basin and the rest of the cavity, (iii) the measurement of the deformations of the massif in contact with the basin, and (iv) the evolution of the rock water content.
All data is acquired, managed and shared with Ineris partners via the e.cenaris monitoring infrastructure.
The experimental site may be visited on request from Ineris.
Schematic view of basin instrumentation
Front view of the basin
(Legend : 1 = Warmwater, 2 = Damm, 3 = Data recorder, 4 = support panel )
In the context of ground movements due to abandoned or natural cavities, instable slopes and other geostructures, for risks prevention purposes, Ineris closely watches technological developments of new remote measurement systems and sensors. Using fixed GPS stations to remotely measure displacements has been used for a lot of applications over nearly two decades. Recently, the development of “low-cost” station networks has increased the potential fields of application. In order to appraise the operability and cost-benefit ratio of this technological evolution, Ineris is performing a high-scale test of GEOMON firstname.lastname@example.org
GEOMON system consists in combining several differential GPS devices versus a local reference one. In addition, a base station ensures the calculation of the location of each device and the FTP connection. The system is power-self-sufficient (using solar panels) and it enables to simultaneously follow up to 15 points within a 1500-meter radius around the base station.
Respect to other systems based on the same technology, GEOMON system can be easily and quickly implemented (“plug and play”). Its low cost for three-direction centimeter-accurate measurements is also one of its characteristics.
The first test phase (from March to September 2016) enabled to assess the deployability of the system and to perform blind tests in order to independently determine the measurement’s accuracy. In a second phase, the system has been installed on a pilot site, where substantial ground movements are expected, together with a proven RTK GPS in order to control the performance. Since September 2016, three points are daily measured on site (during 1 hour / day), i.e. two devices are used to follow the ground movement while the third is used to monitor the water level variations of a lake located nearby.
Ineris is one of the partners of SLOPES (Smarter Lignite Open Pit Engineering Solutions), a European research project, funding by the RFCS (Research Fund for Coal and Steel) and started in July 2015. The SLOPES project brings together experts from across Europe to advance the current technology and methodologies applied to monitoring and risk analysis of slopes within open pit lignite email@example.com
Modern techniques (such as UAVs or drones, LiDAR, etc..) which aim to overcome the challenges of monitoring within open pit mines will be deployed and tested within real mines and results will be compared against physical model tests as well as rigorous numerical modelling. A reliability-based method for the evaluation of risks will be developed based on monitoring and modelling results which will provide significant benefits to design optimisation and decision support within real open-pit lignite mines.
In addition, the SLOPES project will design and implement a monitoring scheme as well as an intelligent data management and early warning system. The project will define criterion (displacement, velocity, etc.) for helping the mine authority to manage the mine under safety conditions.
Ineris will work on the deployment of UAV and LiDAR technologies, on the implementation of a web-monitoring multi-parameter system and numerical modelling.
The aim of the CascEff FP7 European Project is to improve our understanding of the cascading effects in crisis situations, in order to reduce the consequences of escalating incidents in complex environments. To this purpose, the project works on the identifications of initiators (both natural and anthropic) dependencies, and key decision points. These are used to develop an Incident Evolution Tool (IET), which will enable improved decision support in escalating incidents, contributing to the reduction of collateral damages and other unfortunate consequences associated with large firstname.lastname@example.org
In addition to contributing to the development of the IET, Ineris works on the strengthening of its network of monitoring and data-transfer systems relative to crisis management in the context geotechnical hazards. To this purpose, engineers and technicians are working on the data fusion technologies to be implemented on multi-variable alarm systems. Such developments are realised with the e-infrastructure e.cenaris and applied to Ineris observation and operational monitoring.
SOLVAY is mining salt in Tuscany, Italy, since the early 20th century. Nowadays, SOLVAY processes solution mining in two salt mining concessions in a rather complex deposit composed of salt lenses underlying 170 m to 300 m deep. The exploitation scheme relies on a regular network of deep boreholes enabling air and clear water injection with brine extraction till the underground communication between boreholes. The brine is transported through pipeline up to the SOLVAY Marittimo chemical plant located at Rosignano.email@example.com
Such a solution mining method induces periodically ground failures originating from the underground cavities created by the dissolution process, sometimes along with landslides. These geohazards raise a risk for the mining staff operating periodically on surface along the access tracks and working zones (drill heads, engineering structures and networks).
To better manage and prevent those geotechnical risks, SOLVAY has entrusted Ineris, in 2015, to the operational management of the microseismic monitoring network based on the e.cenaris web infrastructure. The solution aims to yield early warnings related to underground failures propagating upwards till the surface, relying on the routine analysis of the seismic activity. This strategy provides the best approach for the safety at work in such a mining context.
REN-Armazenagem company (REN group – Energy National Network), in charge of the transport of power and gas in Portugal, is one of the concessionaire companies working for the underground storage of natural gas in Carriço. It supervises the exploitation of six salt caverns, located between 950 and 1370 meters firstname.lastname@example.org
By the end of 2014, Ineris has been appointed by REN to set up and to manage a near-to-real time microseismic monitoring system in order to monitor the stability of the caverns and to better prevent industrial risks. Ineris will ensure the administration of the system and the data analysis and expertise on a pluriannual basis by means of its internet infrastructure e.cenaris.
Ineris, within the framework of the FP7 European project I2Mine and in partnership with the Swedish mining enterprise Boliden, has developed and installed in Garpenberg mine (Sweden) new methodologies and tools related to stress and microseismic measurements in order to monitor the induced stress fields in deep email@example.com
Such study aims at introducing cross analysing methods in near real time together mine working data, which provide an overview of the progression of the exploitation of the drifts/floors inside the mine, by means of explosions, ore extractions and potentially stowing activities of the emptied volumes, with geotechnical and geophysical data measured continuously during these operations. Indeed, we would like to highlight whether stress variations and seismic sources behaviour might be directly bound with mine working evolution in order to improve our knowledge on the response of deep mining cavities to the exploitation solicitations and to develop, if possible, methods to prevent from major hazards such as rock bursts or collapse phenomena.
In the framework of the European Project MARsite FP7 (Supersite EU initiative http://marsite.eu/), started in 2012, Ineris, University of Istanbul, IFSTTAR, CERI-Sapienza, KOERI, TUBITAK have, thanks to the help of the Community of Istanbul, successfully installed a local multi-parameter ground monitoring system on an important active but slow landslide (so-called Beylikdüzü pilot site) located in the heart of a densely urbanized area part of the Cekmece-Avcilar firstname.lastname@example.org
This large landslide prone area is located westwards of Istanbul, and shows high susceptibility to both rainfalls while being affected by very significant seismic site effects as shown by the 1999 Izmit and Duzce earthquakes.
Main objective of this field observatory is to build and yield to the partners a unique dataset of long term observational time series aiming to improve our understanding of the seismic landslide mechanism in this specific geological setting. Recorded data shall open new gates ranging from calibration of advanced dynamic numerical modeling, rendering the failure mechanism scenario more transparent, to the assessment of Early Warning Technologies.
The mine of St-Jean-de-Maruéjols-and-Avejan (Gard, southern France) exploited, by rooms and pillars, the asphaltic limestones of the Oligocene filling of the Alès trench. The work was performed during the 20th century, from the surface down to 230m depth. These lands being aquifers, it was necessary to drawdown the watertable by continuous pumping during the exploitation. After the closure of the mine, pumping was stopped and the water invaded the underground galleries, creating a mining aquifer of about 1.5 million m3. Most exploited panels have collapsed, creating a decimeter-scale subsidence. The subsequent flooding of the mine induced a maximum water rise of about email@example.com
Farmers now want to capture this water resource at a flow rate of 300m3/h, which is likely to create a drawdown of 80 m. In accordance with the DREAL Languedoc-Roussillon, a pumping trail lasting a few months was set up to measure both the induced drawdown and the movement of the ground surface. These are followed through by two complementary techniques: 1) precise leveling of 31 points performed every week by an expert geometer, and 2) continuous ground motion measurement of two GPS tags implanted by Ineris in the most sensitive places.
This protocol has been followed by the Prefect and alert thresholds have been established.
In the recent years, new modes of storage operation are observed in salt caverns with higher frequency cycling. It is the case for Natural Gas Storage and Compressed Air Energy Storage. With these higher rates of injection and withdraw, the temperature variation in the caverns are also firstname.lastname@example.org
To evaluate the consequences of such temperature variation, a project has been proposed to perform a full instrumented thermal fracturation test of salt in real scale in a dry mine. The project is sponsored by Solution Mining Research Institute’s founding and lead by Storengy. The other partners are Salins du Midi, Ecole des mines de Paris, University of Hannovre and Ineris. The main objective is to create fractures with cooling and prove that fracture depth remains small, even after several thermal cycles. The experimental device is constituted by a fridge chamber in a single galley to cool the floor on 10 square meters. To follow the cooling field and the strain field, the rock mass of salt is monitored with strain and thermal sensors. To follow the fractures, an ultrasonic network is listening the Acoustic Emissions and a camera network is observing the cooled surface.
The concept of reference to seal the galleries of Andra for the purpose of fluid storage consists of a core composed of swelling clay. Massive concrete supports provide axial mechanical confinement of the core during re-saturation, to ensure the best radial swelling email@example.com
The objective of this experiment “Noyau de SCellement” (Sealing Core) is to evaluate the hydraulic performance of the sealing core near field. The concrete support will be subjected to significant mechanical stress and is dimensioned to withstand the thrust of the sealing core. One of the challenges is to verify in situ if the large radial pressure generated by the core can damage the concrete support. Ineris, in scientific partnership with ANDRA, designed an ultrasonic monitoring system to "listen" to acoustic emission generated by damage in the concrete structure and possibly in the host rock. A portion of the device has been installed in the concrete before casting and the other portion on the wall’s face. In the case of this experiment, the information collected by the central sensor also enables to verify a velocity model and to accuracy localize events. This is a first step in the monitoring of acoustic emissions and possible changes in the velocity field during the experiment, physically associated with localized fracturing of the material.
It is a first step in monitoring acoustic emissions and change of the velocity field during the experiment physically associated with localized rupture of the material.
Présentation du site expérimental de Catenoy (Oise) et impact d'une fuite simulée de CO2 dans l'aquifère de la craie.
Microssismique des glissements de terrain dans les roches argilo-marneuses.
Sismicité induite dans différents contextes d'exploitation du sol et sous-sol.
L'utilisation des corrélations de bruit de fond sismique pour suivre les processus dynamiques dans l'exploitation des mines profondes.
Hydrogéologie des versants instables profonds.
Etude détaillée de l'ancien basin houiller de Gardanne.
InSAR data: why we should care.
Analyse et interprétation de la microsismicité induite par l’effondrement provoqué d’une cavité saline créée par dissolution : une contribution pour progresser dans l'évaluation des risques d’instabilité de cavités souterraines.
La surveillance de cavités par méthode acoustique.
Développement d’un modèle analytique d’interaction solstructure pour l’étude du comportement mécanique des structures soumises à un mouvement de terrain – influence des déformations de cisaillement et de la plasticité
Modélisation numérique de la redistribution des contraintes et des affaissements de surface pour évaluer la prédisposition aux coups de terrain autour des panneaux de longue taille : Etude de cas de la mine de charbon de Provence, France
Casque en tête, pénétrez dans une mine réduite et explorez-en les coins et recoins pour y détecter des tremblements ou des effondrements. Initiez-vous à la sismologie en découvrant les techniques d'enregistrement des vibrations du sol et apprenez à reconnaître des signaux.
Réservation en ligne, limitée aux 120 premiers inscrits : https://tcs.ah-epos.eu/login.html
1-2 Septembre 2016, à Mines Nancy, Campus Artem
Origine de la sismicité de l'ancien bassin houiller de Gardanne : apport de l'analyse des mécanismes à la source, par Jannes
Amélioration de la prévision du risque sismique dans les mines profondes, par Francesca.
Etude des effets de l'eau sur les phénomènes de rupture et de déformation affectant les carrières souterraines de craie.
Présentation de la suite logicielle SYTMIS: Mécanismes et paramètres à la source sismique.
"Gestion Verte" des rejets d'eau et de gaz dans les activités minières.
Présentation du système IBIS-FL avec résultats de Séchilienne et du système IBIS-FS.
Explicit modeling of initiation and propagation of fractures
The study of the behavior of rocks requires understanding their response under various stresses. The energy study of rock damage is essential in order to predict dynamic phenomena. These phenomena are due to the development of cracks in the rocks subjected to strong initial and induced stresses. Fracturing is a form of energy dissipation that restores the balance of the environment.
The aim of the thesis is to model the cracks in rocks and study the behavior of underground structures at great depths. The development of models able to simulate the fracturation, coalescence of cracks and their interaction with pre-existing fractures is essential. From the literature, there are two main theoretical and numerical approaches to crack modeling: continuous and discrete. A critical synthesis of these approaches has led us to choose the discrete approach and more particularly the code named Yade. This code enables to simulate explicitly the cracks propagation with or without pre-existing fractures. Developments have been made to evaluate the different forms of energy involved in rock behavior. In particular, a correlation between the cracks energy determined numerically and the microseismic activity observed in laboratory samples. The various energy components developed and then implemented in Yade are: external work, potential energy, elastic energy, friction energy, cracks energy, kinetic energy and damping energy. Validation of the energy approach was carried out by simulating laboratory tests. The evolution of the various energy components permits to verify that the energy balance is correctly evaluated. The energy balance was also verified on a large scale by simulating the underground excavation of a Mine-by Experiment (URL Manitoba). The extension of the damaged zone excavation predicted numerically was compared with that observed in-situ around the Mine-by Experiment. It has been found that the predicted damage is similar to that observed in the minor and major initial stress directions. In addition, the energy formulation enables to study numerically the fracturation process of rocks. Wassermann (2006) performed uniaxial and triaxial compression tests on samples of iron ore from Lorraine. We have modeled these tests. The qualitative comparison of acoustic events and cracks energies determined from tests and numerical simulations showed similar trends. On the other hand, the quantitative comparison showed that the number of numerical acoustic events is greater than the number of experimental acoustic events. Also, the energy dissipated by cracks determined numerically is greater than the cracks energy measured in the tests. This difference is explained by the fact that the sensors of the experimental device do not detect all the acoustic events. A good correlation is obtained between the numerically calculated cracking energy and the microsismic activity observed in the laboratory for the Lorraine iron ore samples. The results obtained will allow us to better understand the dynamic phenomena in the deep underground structures. Another application was to model an iron ore pillar of Joeuf (Lorraine). The numerical model shows two modes of cracking in the pillar: (a) flaking of pillar wall, (b) two breaking bands initiating from the wall and roof of the pillar to propagate towards the core of the pillar. This provides good prospects for better understanding the cracks propagation on a larger scale.
Francesca De Santis, PhD student at Ineris – GEORESSOURCES and Lorraine University (France), cosupervised by IPG Paris (France) and BOLIDEN (Sweden), has been primed twice in 2017 for her research work on microseismic data analysis applied to the seismic risk assessment in deep hard rock mines. Her research is leaded in collaboration with the Garpendberg Mine staff.
First award was received at the ETH Zurich international workshop on induced seismicity at Davos, march 2017. Second award was won in November 2017, Santiago, Chili, during the RASIM9 international conference on induced seismicity and the rock mass response to mining and underground construction.
Ineris is participating in the RaSiM9 2017 event. Ineris will show its technologies - hardware and software - and services for advanced monitoring in mining, post-mining and underground operations. Ineris solutions range from stand-alone to networking systems, integrating geotechnical, geodesic and microseismic monitoring. Cost-effective solutions are designed to support ground engineers, operators and stakeholders involved in the mitigation of georisks including induced seismicity, failure of geostructures and geo-environmental issues.
Binôme est la rencontre entre un scientifique et un auteur de théâtre. L’un consacre sa vie à la recherche, l’autre à l’écriture. L’un se raconte, l’autre le questionne, ils ont 50 minutes chrono.
Effondrement(s) de Lucie Depauw, est écrit à la suite de sa rencontre avec Isabelle Contrucci, ingénieur à la Direction des Risques du Sol et du Sous-sol de l'INERIS.
Improving seismic risk prediction in deep mining operations
Knowledge review concerning hazards and risks related to Anthropogenic Seismicity
When : 13 December 2018.
Where : Mines Nancy, Campus ARTEM, France.
Within GOR meetings, a presentation will be held by Isabelle Contrucci, Engineer at Ineris, on Thursday the 13th of December at 12:00 in Mines Nancy, Campus ARTEM. This presentation is entitled “Knowledge review concerning hazards and risks related to anthropogenic seismicity”. This is part of a synthesis work that was performed for the Ministry of Ecological and Solidary Transition and which led to the production of a downloadable report (click here : in French, in English)
Free access. For registration (compulsory), please contact :
Ineris and GeoRessources are pleased to announce the 3rd edition of OSR2G Worskhop.
This event will focus on the technical challenges of in situ stress measurements and their practical applications in geosciences, mining and civil engineering.
Date: 21-22 November 2018.
Venue: Mines Nancy, Campus ARTEM, France.
Participation is free although registration is mandatory.
Online registration: https://osr2g.sciencesconf.org/
Full program available.
Gilles Armand, PhD (France)
Daniel Ask, PhD (Sweden)
Robert Corthésy, PhD (Canada)
Matti Hakala, Res. Eng. (Finland)
Maria-Helena Leite, PhD (Canada)
Ove Stephansson, Prof. Dr. (Germany)
Ineris: C. Balland, C. Bouffier, J.-B. Kazmierczak, E. Klein
GeoRessources: M. Conin, Y. Gunzburger
21-22 November 2018, Mines Nancy, Campus Artem (Nancy, France).
In the framework of GOR meetings organized by Georessources department, Romuald SALMON and Christian BOUFFIER, engineers at the Ineris, will present their work carried out on the topics of Resilience and Critical Infrastructures. In particular, they will speak on the principles and methodologies developed within IMPROVER H2020 project.
This meeting is open to everyone, though registration is needed.
On May 14th, on the initiative of the House for Science of the University of Lorraine, Ineris participated to an awareness day addressed to the teachers in natural sciences of the Lorraine Region. The meeting was held at the Salt House (la Maison de Sel).
The day aimed at presenting one geological resource of the Lorraine territory, i.e. the salt, and its exploitation.To this purpose, Isabelle CONTRUCCI, our expert, held a conference on the research works performed by Ineris on the provoked collapse of the salt cavity of Cerville Buissoncourt. She was accompanied by Hervé MARTIN, from SOLVAY exploiting company, who presented the salt dissolution exploitation methods used on that site and the environmental actions which were performed for its conservation.
Ineris Ground and Underground Risks Division recently acquired a latest-generation 3D laser scanner and completes thus its range of auscultation and monitoring tools. This 4-km-scanning-range tool enables to produce 3D topographical surveys with millimetric accuracy. Capable of acquiring up to 222.000 measurement points per second, the on-board computer performs innovative data processing, especially for big geostructures and in case of bad weather conditions. The aim of this tool is to give the possibility to perform new research and study projects regarding, among others, the impacts of the climate changes on the stability of rocky front edges located in hard reachable places.
On March 26th, Artem Entreprises, a Lorraine gathering association of the three Artem schools and of about forty citizen enterprises, visited the National Monitoring Center for Ground and Underground Risks (Cenaris) of Ineris. Located inside Nancy School of Mines, the mission of this research and expertise center is to develop and to implement ground and underground scientific observation methods, as well as monitoring and early-warning devices. Since 2006, the Cenaris is involved in French and international projects.
This visit, which was organized by Mrs. Raphaëlle Friot – Artem coordinator and administrative officer of Artem-Nancy, and Mr. Olivier Crancée – president of Artem Entreprises, gathered around twenty participants. It was followed by a discussion time about risk management and public and industrial safety.
Date : Le 14 mars 2019
Lieu : Paris
Le 14 mars 2019, le Comité français de mécanique des roches (CFMR) organisait une séance technique à Paris, sur le thème de la sismicité induite.
L’institut a été sollicité pour présenter l’état des connaissances sur le lien entre activité industrielle et sismicité, notamment en ce qui concerne les phénomènes en jeu et les solutions de gestion de l’aléa et du risque. Il s’agissait notamment de restituer un important travail de synthèse réalisé en 2017, dans le cadre de la mission d’appui de l’Ineris aux pouvoirs publics.
Une vue d’ensemble sur cette problématique ainsi que des cas d’applications sur lesquels travaille l’Ineris ont été présentés.
Date : February 05, 2019.
Place : Mines Nancy, Campus ARTEM, France.
Candidat : Francesca De-Santis
Jury composed by :
Beata ORLECKA-SIKORA, Associate Professor, Institute of Geophysics, Polish Academy of Sciences – Rapporteur
Martin GRENON, Professor, Université Laval – Rapporteur
Evelyne Foerster, Cadre scientifique d’EPIC, CEA – Examinatrice
Katshidikaya Tshibangu, Professor, Université de Mons – Examinateur
Yann GUNZBURGER, Maitre de conférences, Ecole Nationale Supérieure des Mines de Nancy – Directeur de thèse
Pascal BERNARD, Physicien du Globe , IPGP – Co-directeur de thèse
Isabelle CONTRUCCI, Cadre scientifique d’EPIC, Ineris – Encadrante
Savka DINEVA, Professor, Luleå University of Technology – Invité
Anders NYSTRÖM, Engineer, BOLIDEN – Invité
Seismicity in underground mines is the result of stress perturbations and rock fractures induced by excavations. In the last decades, the problem of mining-induced seismicity has become more and more important due to the increasing depth of underground mines. Understanding mining-induced seismicity is, then, a fundamental purpose for improving seismic hazard assessment in deep mining operations, for mine infrastructure stability and mine workers safety.
With the aim of better understanding interactions between stress modifications induced by mining and the generation of seismic activity, a deep area of Garpenberg mine (Sweden) was instrumented by Ineris with microseismic probes and geotechnical cells. The main objective of this thesis is to realize a comparative analysis of the recorded seismic and geotechnical data, along with a 3D numerical model, taking into account the mining sequence and the geological conditions.
As a first major contribution of this thesis, recorded microseismic activity between 2015 and 2016 (~700 events) has been analyzed and interpreted. Results show a clear dependence between blasts and microseismic events, even if the rock mass response to mining appears to be very variable across space and time. Two seismic clusters are observed: one located in the major production area (Central Cluster) and another (Right Cluster) located at some distance from the excavations, in a zone characterized by a heterogeneous distribution of weak (talc) and stiff (limestone, polymetallic ore) rocks. Seismic source parameters analysis demonstrates that the two clusters are characterized by different dynamics, with Right Cluster events being mainly controlled by geological heterogeneities. Indeed, weak rocks impose high stress concentrations in the stiff rock masses, inducing a mechanism of stress transfer from the exploitation area toward the weak zone.
Geotechnical data analysis shows important strain changes throughout the study period, whose intensity seems to be more correlated with mining sequence and the proximity of weak geological zones than to the amount of extracted rock mass. Geotechnical measurements also show that mechanisms of differed strains take place at Garpenberg mine, and that seismic activity decays proportional to the decaying rate of measured strains. This latter observation implies that, in addition to the immediate stress change induced by blasting, aseismic creep may be another mechanism driving seismicity at Garpenberg mine.
A 3D elasto-plastic geo-mechanical numerical model was run considering a precise reconstruction of the geology, the virgin stress state and the mine sequence. The model simulates 70 excavation steps. The results show how the mining sequence, with one column of stopes being exploited upward and downward simultaneously, leads to high stress concentrations in the remaining pillar and to strong plastic deformation within the weak rocks.
In the last part of this thesis, model results have been compared with seismic data analysis to investigate whether correlations exist. Results shows that mine-wide numerical models can be suitable for the analysis of mining induced seismicity at large-scale. However, there are some aspects of the induced seismicity that the model cannot fully explain. This is particularly true for remote seismicity occurring at a distance from excavations, while better correlations are found when considering seismicity close to production areas. Further analysis will be needed in future works to deeper characterize remote seismicity and found appropriate constitutive law able to represent it within the model.
Dans le cadre du programme d’appui au Ministère de la Transition écologique et solidaire relatif à la prévention des risques naturels, l’Ineris exerce une veille scientifique vis-à-vis de dispositifs de mesures émergents et novateurs sur le marché.
En 2016 et 2017, l’Ineris a testé un dispositif conçu pour la télésurveillance instrumentale de mouvements de terrain.
Le dispositif se compose d’un réseau de modules GPS, permettant l’acquisition des signaux GNSS, et d’une station de base assurant les calculs des positions et la connexion GSM ou Ethernet. L’ensemble des éléments sont autonomes (alimentés par panneaux solaires). La transmission des données entre les modules GPS et la station de base est assurée par une communication radio.
À comparer aux technologies existantes basées sur la mesure GPS, ce type de dispositif se veut innovant de par son coût très maîtrisé, sa mise en oeuvre simplifiée et une précision centimétrique.
Les tests ont été réalisés sur les bordures des effondrements (exploitation de sel) du site de SOLVAY à Cerville et Haraucourt (54). Des modules GPS ont été implantés dans des zones connues comme actives ou considérées comme stabilisées. Un test « forcé et en aveugle » a également été réalisé.
L’objectif de cette instrumentation a été d’évaluer :
• la précision des mesures de position ;
• la mise oeuvre du dispositif sur site ;
• la gestion du suivi à distance ;
• la fiabilité des mesures et la robustesse du matériel dans le temps ;
• les limites éventuelles du système.
Les mouvements de grands versants font partie des risques naturels majeurs, dès lors que les populations et les infrastructures sont menacées. La prévention de tels mouvements n’est pas aisée, dans la mesure où les phénomènes sont amples et les mécanismes physiques sont complexes, parfois brutaux, difficiles à observer en continu et à étudier.
Le mouvement de versant « des Ruines de Séchilienne » est à ce titre emblématique. Il est situé à une vingtaine de kilomètres au sud-est de Grenoble, en rive droite de la vallée de la Romanche. Son instabilité en masse pouvait notamment conduire à l’obstruction de la rivière, ainsi que la coupure de la route départementale 1091 (ex RN 91) desservant les stations de l’Alpe d’Huez et des Deux-Alpes, ainsi que le col du Lautaret et Briançon.
Dès 1985, le site a fait l’objet d’investigations techniques et scientifiques dont les résultats ont permis de faire une première évaluation de l’aléa géologique et hydraulique. En 1986, au vu d’une accélération du phénomène, un dispositif d’alerte opérationnel a été installé par le CETE de Lyon (actuel Cerema Centre-Est) à la demande de l’Etat.
Entre 2009 et 2016, l’Ineris, dans le cadre de son programme d’appui au Ministère de la Transition écologique et solidaire, et en partenariat avec le Cerema, a contribué aux investigations sur ce mouvement de versant par la mise en œuvre d’un dispositif automatique d’observation multi-paramètres (géodésique, géotechnique et microsismique) en quasi temps réel, et placé en bordure ouest du secteur actif.
Le présent rapport, destiné aux acteurs qui interviennent dans la gestion du risque de « mouvement de versant » par la surveillance, décrit les apports technologiques et méthodologiques de l’observation menée par l’Ineris, et fait la synthèse des enseignements qui ont été tirés.
keywords: Industry, mines, hydrocarbons, geothermal, seismicity, hazard, risk, management, social acceptance.
The relation between underground industrial activity and seismicity has been highlighted at the beginning of the twentieth century in the deep gold mines of South Africa. Today, as the demand for mineral resources and energy keeps increasing, the number and size of industrial projects as well as new emerging underground industries that can potentially induce seismicity is also raising. Some of the most illustrating cases are presented in this report. This report also deals with the issues related to seismic hazard assessment, risk mitigation and emerging regulations in the context of anthropogenic seismicity.
The mechanisms of anthropogenic seismicity are now relatively well understood, and researchers suggest distinguishing induced events which results from the anthropogenic underground disturbance itself, from triggered events, which are related to the reactivation of natural geological faults due to industrial activity. In some extreme situations, anthropogenic seismicity can endanger public safety, especially when man-triggered earthquakes occur in regions with low natural seismicity and poor seismic prescription and sensitivity of the populations. In addition, social acceptability can quickly be challenged, and lead to the cessation or abandonment of industrial projects even when only rare earthquakes with very low intensity are felt. In some cases, induced seismicity can persist long after the ending of the underground operations. It can even occur several kilometers from the operations. These situations have been observed especially during fluid injection and extraction activities. The so-called triggered seismicity remains the potentially most destructive threat to public safety.
Currently microseismic monitoring has become a prominent tool for managing the risk of anthropogenic seismicity. The near to real-time processing of microseismic data, coupled with the monitoring of industrial parameters offers a helpful approach to decision making. Similarly, solutions exist to reduce the vulnerability of buildings and infrastructures, when the relocation of the project is not possible. Regarding the safety of minors at work, operators have developed numerous approaches to limit worker exposure.
Both the world of industry and the world of research are nevertheless facing several challenges. One of them concerns the characterization of the anthropogenic seismic hazard and the capability to distinguish natural earthquakes from anthropogenic earthquakes. This is of obvious interest for all parties involved; it may also have a significant impact in terms of responsibility of the operator. The success of future deep projects depends obviously on how well anthropogenic seismicity is managed and communicated to be acceptable to all stakeholders.
keywords: Underground cavities, natural and anthropic seismicity, gravity hazards
French territory is largely exposed to the risks of underground cavities. Some of them are subjected to anthropic or natural solicitations like seismic vibrations that could affect their stability in the long term. The objective of this study is to estimate the impact of those vibrations on shallow underground cavities and on the underground space located between the surface and several tens of meters deep, as they may induce ground movements (subsidence, crown-hole, sinkhole, etc.).
Based on a wide national and international bibliographic study, vibratory sources that may affect the stability of underground cavities (earthquakes, explosions, machines, traffic) are presented and discussed. We then describe the dynamic phenomena involved.
Among the different vibratory sources, it turns out that major earthquakes have the potential to destabilize the underground cavities during a single event and that a weaker but repeated seismic event can damage a little more a rock mass already fractured. Mechanical models for room-and-pillar underground excavation make it possible to estimate this impact, and the probability to collapse the pillar or the roof of an underground mine as a function of its depth and the intensity of the seismic loads.
Vehicles and construction equipment can also induce significant stresses when located in the immediate vicinity of underground cavities (particle velocity greater than the prescribed particle velocity of 10 mm/s). The traffic generates movements of low particle velocity (less than 3 mm/s) even at very short distances; it can only affect very sensitive structures or already close to ruin.
This document finally presents the preventive actions that could be envisaged to limit the impact of vibrations. It also shows the importance to consider the fatigue of underground and underground structures abandoned at low depths.
Keywords: monitoring – underground cavities – rockfall – treatment - methods
Wide areas and tens of thousands of communes in France are concerned by the risks related to underground anthropogenic (i.e. human-built) cavities. Sustainable solutions do exist, such as voids landfilling. Monitoring underground cavities can be used as a palliative and transitory tool, though.
The guide for the monitoring of underground anthropogenic cavities is a document produced by Ineris for the French Ministry of the Environment, the Ecology and the Sea (“MEEM”) to be addressed to the territorial collectivities and any field project manager that might face whether to use monitoring technologies or not.
This guide mentions the points that may be discussed before considering monitoring. First, the feared instability phenomenon must be known and correctly assessed. Second, how long monitoring will be performed should be considered: either for emergency, for short-term, or for more sustainable periods, before more stable risk management solutions are fixed. Then, access conditions and facilities to the site, security rules and transmission ways should be considered to decide whether to implement monitoring locally or in a remote way.
The monitoring project can start once these preliminary points are well understood. Several equipment solutions area available. They are briefly presented in the main section of the guide and are detailed in didactic documents in appendix.
Visual surveys are fundamental and to be performed as soon as it is possible to access to the site in acceptable security conditions; they are by the way often considered. Using additional tools such as photogrammetry or laser scanner is sometimes necessary to observe some evolutions which are hardly visible to the naked eye. In addition, geotechnical measures enable to directly assess local physical characteristics such as displacements, pressures, water levels… while geophysical sensors are used to monitor wider areas, thanks to remote measurements, i.e. by detecting the waves linked to any evolution and instability through the rocks or the underground voids.
To be effective, not only monitoring must be operational, but also all its constituting elements must be mastered: measurement devices, data transfer processes, maintenance and organization procedures. Monitoring might be based on meaningful alarm thresholds, corresponding to a possible prejudicial instability evolution, in order to alert the project managers or collectivities if necessary. The maintenance and the continuous follow-up of the equipment should also enable to detect any dysfunction along the measurement chain. Data sharing and transmission finally facilitate more rapid analysis and thus provide with feedbacks by taking into account the historical data.
Keywords: underground cavities – rock fall - surface effects - treatment - methods
Ineris provides people involved in land use and planning with a technical guide on procedures to ensure safety of the fields located over abandoned underground cavities. This guide was produced in the framework of the French National program for the prevention of risks related to collapse of underground cavities (“Cavity National Plan”).
This guide is addressed to local administrations and politicians, sites stakeholders and managers. It presents the most used processing methods to make surface fields secured, which are exposed to collapse hazard because of the presence of abandoned human-excavated cavities: carries, chalk mines, underground shelters, troglodyte houses, war sapping structures, etc. These methods are applicable not only for prevention (i.e. the presence of underground voids is known, however no disorder has affected the surface yet) but also for managing collapsing incidents (e.g. sinkhole formation). They are classified into two categories: the first methods consist in directly working on the cavity, the second ones are used to limit the surface effects induced by the presence of the cavity.
Underground cavities are at the origin of various risks of ground movements such as collapses and subsidences. A sinkhole is a “located” collapse, a phenomenon peculiar to cavities situated at shallow depths. This kind of risk, which widely affects most of the national territorial regions, covers the main part of the natural and anthropological cavities: post-mining, abandoned quarries, marlpits, karsts, tunnels and abandoned civil works, etc.
Nowadays, the supervision of these phenomena is essentially realized by visual inspection and by conventional geotechnical instrumentation. These steps present limits, particularly in terms of appreciation of the phenomena kinetics. In the context of a research operation financed by the Ministry of the Environment, and of Sustainable Development and Energy (“MEDDE”) as well as the European Regional Development Fund (ERDF), the institute Ineris tested and estimated acoustic detection as an innovative instrumental technique used for the cave-in risk evaluation. The present report synthesizes these works by detailing more-or-less:
the conception of equipments necessary for the underground cavity measurements;
full-scale tests on a pilot site and operational feedback experience;
identification of the advantages and limitations of this technique.
Keywords: microseismic monitoring - mining collapse - signes précurseurs - mécanismes de rupture - atténuation - interaction fluide / roche
In some cases, site supervision appears as the best compromise for the post-mining risk management for several types of ground movements. It mainly leans on systems of real time microseismic surveillance of the concerned zones. The purpose is to detect the acoustic emissions which may present precursor signals for a large-scale collapse phenomenon. Applied to public security since 1998, this type of supervision method was employed on more than about thirty networks destined for real time microseismic supervision within the Lorraine ferriferous mining region.
The present report aims to exploit and highlight the information contained in the microseismic signals, in correlation with other types of measurements whenever available, in order to:
progress in the identification of the precursor signs for an eventual collapse;
characterize mechanisms and dynamics of the collapse , particularly the presence of a stiff rock layer in the cavity overburden structure;
emit recommendations for the operational supervision management.
This report joins within the framework of the research project PR190 “Phenomenology of the geological instabilities in full-scale and precursor signs” introduced in 2007 and continued since 2010 within the framework of the research COSMOS (Comprehension, Modeling and Supervision of the deformation style of rock ruptures).
Keywords: unstable slopes - ground-based monitoring - interferometric radar - scan ground laser - risk-management - mobiles systèmes
For the protection of populations and infrastructures, the principal management actions for hillside risk instabilities, often rest on active hazard supervision, by regular field inspections and also implementation of in situ instrumentations.<br>The present report makes a review of the innovative supervision methods of full-scale hillside instabilities, compatible with portability requirements and operational supervision. The study is focused on interferometry RADAR and long-range laser ground measurement techniques , already widely used internationally by open air mine and quarrie exploitations, in the evaluation of instability evolutions, and also by public organizations for natural risks prevention.
This report shows that the conditions of implementation and performances of these two techniques are very different from one another, particularly in their data processing methods; although both are based on a common principle (the device emits signals which are reflected back at the surface of the imaged object. This report specifies the characteristics, the advantages and limitations of each technique across illustrations stemming from the scientific and technical literature. It also supplies elements of costs and recommendations for the optimal conditions of implementation of each method.
This study is registered in the framework of the entitled program EAT-DRS06 “National Supervision Center of Ground and Underground Risks”. It is a program of technical support for the Directorate General for Risk Prevention of the Ministry of Ecology, Sustainable Development and Energy.