Detection and monitoring of high stress concentration zones induced by coal mining using numerical and microseismic method

Zones of high stress concentration induced by coal mining at a depth of 1250 meters in the Lorraine Collieries are detected and monitored using a combination of numerical and microseismic methods. Changes in the stress state induced by coal mining are estimated by means of numerical simulations. The areas of high stress concentration are located and monitored by local microseismic network. The study of microseismic activity recorded during mining made it possible to localise the zones of high stress concentration and validate the calculations done by numerical modelling. The results of this study hold out interesting prospects for using a combination of numerical modelling and microseismic monitoring for detecting, locating and monitoring of the zones prone to rockbursts

Imagetic and affective measures of memory reverberation diverge at sleep onset in association with theta rhythm

The ‘day residue’ - the presence of waking memories into dreams - is a century-old concept that remains controver- sial in neuroscience. Even at the psychological level, it remains unclear how waking imagery cedes into dreams. Are visual and affective residues enhanced, modified, or erased at sleep onset? Are they linked, or dissociated? What are the neural correlates of these transformations? To address these questions we combined quantitative se- mantics, sleep EEG markers, visual stimulation, and multiple awakenings to investigate visual and affect residues in hypnagogic imagery at sleep onset. Healthy adults were repeatedly stimulated with an affective image, allowed to sleep and awoken seconds to minutes later, during waking (WK), N1 or N2 sleep stages. ‘Image Residue’ was objectively defined as the formal semantic similarity between oral reports describing the last image visualized before closing the eyes (‘ground image’), and oral reports of subsequent visual imagery (‘hypnagogic imagery). Similarly, ‘Affect Residue’ measured the proximity of affective valences between ‘ground image’ and ‘hypnagogic imagery’. We then compared these grounded measures of two distinct aspects of the ‘day residue’, calculated within participants, to randomly generated values calculated across participants. The results show that Image Residue persisted throughout the transition to sleep, increasing during N1 in proportion to the time spent in this stage. In contrast, the Affect Residue was gradually neutralized as sleep progressed, decreasing in proportion to the time spent in N1 and reaching a minimum during N2. EEG power in the theta band (4.5-6.5 Hz) was inversely correlated with the Image Residue during N1. The results show that the visual and affective aspects of the ‘day residue’ in hypnagogic imagery diverge at sleep onset, possibly decoupling visual contents from strong negative emotions, in association with increased theta rhythm.Neuroimag

Back-analysis of the rockburst in Frieda 5 and design program for panel in seam 6 (HBL-France)

International audienceThis paper develops the studies carried out after the fatal accident occurred during the mining of Frieda5-1250 panel at Merlebach mine section of HBL (East France). On the 21 June 2001, a violent rockburst (local magnitude of 3.6) has affected the panel 1250 of Frieda5 coal seam. An investigation program was carried out to determine the causes of this accident and to understand the induced phenomenon. The program include: seismic investigations, geological and geotechnical analysis and numerical modeling. The objective is to determine eventually the presence of particular geological structures and there role in the initiation of the accident. After the accident, the HBL intended to mine the Seam 6. In order to monitor the behavior of the ground during the mining of the Seam 6, a geotechnical program comprising a complete study of the natural conditions and a seismic analysis was carried out. The environment of the panel is marked by the presence certain number of faults. Stress disturbed by the exploitation of the old panels and the presence of faults are likely to modify the equilibrium of strata before the exploitation and can induced seismicity. To study their influence, the INERIS carried out a numerical modeling in the scale of mine area (SUIT3D and FAULT3D), for the determination of the stress zone induced by old and new panels

Goa, India Collapses of Underground Cavities and Soil-Structure Interactions: Influences of the Position of the Structure Relative to the Cavity

ABSTRACT: This paper is focused on soil subsidence of small extend and amplitude caused by tunnel boring or the collapse of underground cavities, whether natural or man-made. The impact of the movements of the ground on existing structures is generally dramatic. It is therefore necessary to accurately predict these movements (settlements and horizontal extension or compression displacements). Even though it is obvious that the overall stiffness and weight of the structure influences the size and shape of the soil movement, the main features of this soil-structure interaction phenomenon are not well established. Caudron et al. (2006) developed an original smallscale physical model to take the soil-structure interaction into account. It is based on the use of the frictional Schneebeli material (assembly of small diameter rods) and a modified version including cohesion in order to reproduce a cohesive layer above a cavity. The displacements of the soil are obtained from digital images processing by particle image velocimetry (PIV). Interesting results were obtained, probing that the soil-structure interactions could be analysed by this experimental model. This article is focused in a first part on the influence of the position of the structure with respect to the cavity position. Consequences on the areas mainly concerned by horizontal compression or extension of the structure are determined. It appears that the stresses induced in the building are a superposition of several elementary loading (sum of the effects of the slope, the horizontal deformations and the curvature). The second part concerns the effect of the relative soil/structure stiffness on the ground movement during a cavity collapse by considering a second model of structure with similar dimensions but more flexible.

Modélisation numérique de l’interaction sol-structure lors du phénomène de fontis

Cet article présente une étude du phénomène d’interaction sol-structure durant la formation d’un fontis par une modélisation numérique. L’approche utilise un modèle numérique bidimensionnel associant un code de calcul aux différences finies avec un code de calcul utilisant les élémentséléments discrets distincts afin de tirer au mieux parti des performances des deux logiciels. Outre un important gain de temps de calcul par rapport à un modèle constitué uniquement d’éléments distincts, cette approche donne des résultats comparables à ceux observés expérimentalement auparavant

A large 3D physical model: a tool to investigate the consequences of ground movements on the surface structures

Soil subsidence of various extend and amplitude can result from the failure of underground cavities, whether natural (for example caused by the dissolution of rocks by underground water flow) or man-made (such as mines). The impact of the ground movements on existing structures (houses, buildings, bridges, etc…) is generally dramatic. A large small-scale physical model is developed in order to improve our understanding of the behaviour of the building subjected to ground subsidence or the collapse of cavities. We focus on the soil-structure interaction and on the mitigation techniques allowing reducing the vulnerability of the buildings (structures)

Méthodes de prévision des dégradations des structures bâties en zone d’affaissement minier

Les mines et carrières souterraines, en activité ou abandonnées, sont susceptibles d’être à l’origine d’affaissements des terrains en surface. Qu’ils résultent de la méthode d’exploitation ou qu’ils s’avèrent accidentels, ces derniers induisent d’importants mouvements permanents en surface qui peuvent entraîner des dégradations du bâti et des infrastructures. La gestion des zones urbanisées concernées passe par la hiérarchisation du risque de dégradation et la proposition de dispositions constructives, préventives et curatives. Cet article s’intéresse à diverses méthodes de prévision des dégradations du bâti, proposées dans différents pays, qui intègrent des paramètres propres aux terrains de recouvrement, propres à l’affaissement et aux structures. Simples ou élaborées, ces méthodes sont comparées entre elles et confrontées à la réalité. Une étude statistique a été menée sur les affaissements miniers qui se sont produits dans le bassin ferrifère lorrain dans la dernière décennie. Regroupant près de 400 individus (constructions), elle met en évidence l’existence de corrélations importantes entre les dégradations et certaines variables caractéristiques de l’affaissement ou de la structure. Il est alors possible d’élaborer une méthode de hiérarchisation du risque de dégradation, propre au bassin ferrifère lorrain

Détection et surveillance des zones surcontraintes par des méthodes sismo-numériques

International audienceDetection and monitoring of high stress concentration zones induced by coal mining at a depth of 1250 meters in Lorraine Collieries, are carried out by coupling numerical and microsismic methods. Estimation of changes of state of stresses induced by coal mining is carried out by using of numerical modelling. Location and monitoring of high stress concentration zones are obtained by a local microsismic network. The study of microsismic activity recorded during coal mining made it possible to locate high stress concentration zones and to validate results from numerical modelling. The results of this study open interesting prospects with regards to coupling numerical and microsismic methods as a means of detection, location and monitoring of the zones prone to rockbursts.La detection et la surveillance de zones surcontraintes induites par l'exploitation de charbon à 1250 metres de profondeur aux Houilleres du Bassin de Lorraine sont effectuées à partir d'un couplage entre les méthodes numérique et microsismique. L'estimation des modifications de l'état de contraintes ibnudites par l'exploitation est réalisée par des simulations numériques. La localisation et la surveillance des zones surcontraintes sont effectuées par des réseaux microsismiques locaux. L'étude de l'activité microsismique enregistrée lors de l'exploitation a permis de localiser les zones surcontraintes et de valider les calculs effectués par modélisation numérique. les résultats de cette étude ouvrent des perspectives intéressantes en ce qui concerne le couplage de la modélisation numérique et de l'écoute microsismique comme moyen de détection, de localisation et de surveillance des zones à risque de phénomènes dynamiques

Modélisation des affaissements miniers : influence des tailles

International audienceKnowledge of subsidence engineering is of considerable importance to the planning and development of surface. Subsidence is generally associated with the extraction of minerals and natural resources such as oil, gas and water