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Using analytical and numerical methods to assess the influence of the structural parameters of fractured-rock on controlling water flow in underground excavations
Get PDFWater seepage into underground excavations is one of the most important challenges in aboveground and underground civil works. This phenomenon may hinder the excavation rate, and increase the risk of rockfall from wall of the tunnel and subsidence of aboveground buildings. Since most of the underground and aboveground structures are built in rocky formations, the permeability of the fractured rock mass is the main parameter that determines the amount of discharge that occurs through the rock mass. In this regard, the hydraulic conductivity of rock mass has been focused by many researches to evaluate the fluid flow, and has been studied by empirical, analytical and numerical methods. In the present thesis, the amount of flow through the rock mass has been investigated by using analytical and numerical methods (3DEC software), and due to the practicality of the topic, the amount of inflow rate to the tunnel in the present study is more focused. For this purpose, the tunnel inflow rate and its dependence on the geometrical characteristics of the discontinuities have been formulated using analytical and numerical modelling methods. In addition, the effect of the geometry of joint sets and tunnels as well as the groundwater regime on the amount of inflow rate to the tunnel has been investigated using the response surface methodology and numerical simulation method. In order to ensure the representativeness of numerical models for calculation of the inflow rate to the tunnel, same as what is referred in the literature as REV, a new concept, called STL, has been introduced to determine the representative length of the tunnel in terms of geometric characteristics of discontinuities. Apart from the effect of joint set characteristics on the inflow rate to the tunnel, the effect of rock block geometries such as block volume, block surface and volumetric fracture intensity (P32) on the inflow rate to the tunnel has been investigated by numerical and analytical methods. In this regard, new analytical methods have been developed to calculate block surface area, block volume and volumetric fracture intensity. The analytical method for calculating block volume has been developed to modify previously developed analytical models.
L'écoulement de l'eau dans les ouvrages souterrains est un défi important des travaux de surface et de sous surface effectués dans le domaine du génie civil. En effet, ces ouvrages peuvent retarder les travaux d'excavations, ainsi qu'augmenter le risque de rupture des parois rocheuses de la structure et créer un affaissement des bâtiments. Étant donné que de nombreuses structures (i.e. souterraines et en surface) sont construites en contact avec les formations rocheuses, la transmissivité du massif rocheux est un paramètre clé pour spécifier le débit généré dans les fractures. Afin d'évaluer correctement la transmissivité, de nombreuses investigations considèrent la conductivité hydraulique du massif rocheux à l'aide de méthodes empiriques, analytiques et numériques. Cette thèse de doctorat propose une étude sur le débit d'un fluide à travers un massif rocheux et est essentiellement basée sur des méthodes analytiques et numériques (i.e. logiciel 3DEC) en fonction de l'applicabilité du sujet. Ici, le débit d'entrée à l'intérieur du tunnel est le paramètre principalement ciblé. Le débit entrant dans le tunnel, ainsi que sa dépendance aux caractéristiques géométriques des discontinuités du massif rocheux ont été formulés en utilisant des méthodes de modélisation analytique et numérique. De plus, l'effet des géométries des ensembles de joints du tunnel et le régime des eaux souterraines du débit entrant dans celui-ci ont été étudiés en utilisant la méthodologie de surface de réponse (RSM) et la méthode de simulation numérique. Afin d'assurer la représentativité des modèles numériques appliqués pour le calcul du débit entrant dans un tunnel et demeurer fidèle à la littérature existante sur le REV, un nouveau concept est proposé afin d'identifier la longueur représentative du tunnel en lien avec les caractéristiques géométriques des discontinuités du massif rocheux: le STL. Outre l'effet des caractéristiques des ensembles de joints sur le débit entrant dans le tunnel, l'impact des géométries des blocs rocheux telles que le volume des blocs, la surface des blocs et l'intensité de la fracture volumétrique (P32) sur le débit entrant ont été étudiés à l'aide de ces méthodes numérique et analytique. Dans le but d'améliorer les modèles analytiques antérieurs, de nouvelles méthodes ont été développées afin de calculer la surface d'un bloc, le volume d'un bloc et l'intensité volumétrique de la fracture
Des zones du fleuve Saint-Laurent défavorables à la survie des espèces envahissantes deviennent des refuges pour les poissons indigènes
No full textLe gobie à taches noires est un poisson envahissant qui s’est établi et répandu dans le fleuve Saint-Laurent au cours des deux dernières décennies à la suite de son introduction dans les Grands Lacs
Correction: Espriella, M.C.; Lecours, V. Optimizing the scale of observation for intertidal habitat classification through multiscale analysis. Drones 2022, 6, 140
Get PDFIn the original publication [1], there was a mistake in Figure 10 as published. The x-axis is mislabeled. The data and labels are mismatched. The corrected Figure 10 appears below. The authors apologize for any inconvenience caused and state that the scientific conclusions are unaffected. This correction was approved by the Academic Editor. The original publication has also been updated
Satellite-derived bathymetry using machine learning and optimal Sentinel-2 imagery in South-West Florida coastal waters
Get PDFThis study examines the use of the Multi-Spectral Instrument (MSI) in Sentinel-2 satellite in combination with regression-based random forest models to estimate bathymetry along the extended southwestern Florida nearshore region. In this study, we focused on the development of a framework leading to a generalized Satellite-Derived Bathymetry (SDB) model applicable to an extensive and diversified coastal region (>200 km of coastline) utilizing multi-date images. The model calibration and validation were done using airborne lidar bathymetry (ALB). As ALB surveys are very expensive to conduct, the proposed model was trained with a limited and practically feasible ALB data sample to expand the model’s practicality. Out of the three different sub-models introduced using varying combinations of historical satellite imagery, the combined-band model with the largest feature pool yielded the highest accuracy. The results showed root mean square error (RMSE) values of 8% and lower for the 0–13.5 m depth range (limit of the lidar surveys used) for all areas of interest, indicating the model efficiency and adaptability to varying coastal characteristics. The influence of training sample locations on model performance was evaluated using three distinct model configurations. The difference between these configurations was less than 5 cm, which highlights the robustness of the proposed SDB model. The quality of the satellite imagery is a significant factor that influences the accuracy of the bathymetry estimation. A preliminary methodology incorporating spectral data embedded in Sentinel-2 imagery to effectively select the most optimal satellite imagery was also proposed in this study
Remote sensing techniques for automated marine mammals detection : a review of methods and current challenges
Get PDFMarine mammals are under pressure from multiple threats, such as global climate change, bycatch, and vessel collisions. In this context, more frequent and spatially extensive surveys for abundance and distribution studies are necessary to inform conservation efforts. Marine mammal surveys have been performed visually from land, ships, and aircraft. These methods can be costly, logistically challenging in remote locations, dangerous to researchers, and disturbing to the animals. The growing use of imagery from satellite and unoccupied aerial systems (UAS) can help address some of these challenges, complementing crewed surveys and allowing for more frequent and evenly distributed surveys, especially for remote locations. However, manual counts in satellite and UAS imagery remain time and labor intensive, but the automation of image analyses offers promising solutions. Here, we reviewed the literature for automated methods applied to detect marine mammals in satellite and UAS imagery. The performance of studies is quantitatively compared with metrics that evaluate false positives and false negatives from automated detection against manual counts of animals, which allows for a better assessment of the impact of miscounts in conservation contexts. In general, methods that relied solely on statistical differences in the spectral responses of animals and their surroundings performed worse than studies that used convolutional neural networks (CNN). Despite mixed results, CNN showed promise, and its use and evaluation should continue. Overall, while automation can reduce time and labor, more research is needed to improve the accuracy of automated counts. With the current state of knowledge, it is best to use semi-automated approaches that involve user revision of the output. These approaches currently enable the best tradeoff between time effort and detection accuracy. Based on our analysis, we identified thermal infrared UAS imagery as a future research avenue for marine mammal detection and also recommend the further exploration of object-based image analysis (OBIA). Our analysis also showed that past studies have focused on the automated detection of baleen whales and pinnipeds and that there is a gap in studies looking at toothed whales, polar bears, sirenians, and mustelids
Carbon sequestration and emission mitigation potential of afforestation and reforestation of unproductive territories
Get PDFAfforestation and reforestation can contribute to the mitigation of climate change by increasing forested areas that can actively sequester carbon dioxide from the atmosphere through photosynthesis. The purpose of this study was to assess the potential for carbon sequestration in the ecosystem and in harvested wood products, and associated greenhouse gas (GHG) emission mitigation, following the application of afforestation/reforestation strategies on unproductive lands in the Province of Quebec over an 80-year long period (2021–2101), using the Carbon Budget Model of the Canadian Forester Sector 3. Afforestation/reforestation scenarios without harvesting and scenarios based on establishment of fast-growing species such as hybrid poplar showed the greatest short-term (2020–2040) carbon sequestration potential. Over the 80-year simulation period, plantations without harvesting generated a greater potential for carbon sequestration in ecosystems; after each harvesting event, several decades were necessary to regain any ecosystem carbon loss, which could be compensated only if a proportion of the harvested wood is converted to long-lived wood products, with high substitution effects in other sectors. In the northern boreal zone of Quebec, significant mitigation potential can be expected from the afforestation of open woodlands and poorly regenerated burns, both with or without harvesting. In the southern zone, the need for better data on vegetation succession and carbon accumulation on abandoned farmlands in the absence of plantations was highlighted by this study. This study increases the understanding of carbon sequestration by plantations, and their role as a mitigation strategy to contribute to national GHG emission reduction targets and net-zero carbon objectives
A Surface-Micromachined Levitating MEMS Speaker
Get PDFThis paper presents the design and simulation of a levitating MEMS speaker. The device is composed of a levitating membrane actuated through electrostatic forces using several electrodes and a control system. The absence of supporting anchors allows for a drastic reduction of damping losses and therefore promises higher power efficiency. Simulation results indicate very promising performance
Ville interculturelles au Québec: pratiques d'inclusion en contexte pluriethnique
Get PDFLes changements démographiques récents dans les villes partout dans le monde ont suscité des préoccupations croissantes quant aux tensions interethniques, aux inégalités sociales et à la discrimination raciale. L’une des réponses à ces défis a été de se tourner vers les politiques et pratiques interculturelles.
Cet ouvrage réunit des contributions de différents horizons disciplinaires et professionnels dans le but d’offrir un portrait diversifié des pratiques entourant la conception et la mise en œuvre de politiques et programmes interculturels dans les villes à travers le Québec. En s’intéressant à des villes de différentes régions et de tailles diverses, il souhaite également participer au développement d’outils d’analyse comparative qui pourront être utiles pour les communautés universitaires, professionnelles et politiques.
À un moment de l’histoire où les questions liées à la relation à l’autre sont débattues à travers le monde, ce livre offre un regard novateur et éclairant sur les diverses initiatives mises de l’avant par les acteurs municipaux tout en proposant des analyses à la fine pointe des plus récentes recherches dans le domaine. Sa lecture deviendra un incontournable pour la compréhension des politiques et pratiques interculturelles au Québec
Groundwater recharge over the past 100 years: Regional spatiotemporal assessment and climate change impact over the Saguenay‐Lac‐Saint‐Jean region, Canada
Get PDFProper knowledge of potential groundwater recharge (PGR) and its spatiotemporal distribution are essential for sustainable groundwater management, especially within the context of climate change. Here, a robust GIS-based water budget framework was developed to estimate PGR at a regional scale and map its spatial distribution. This framework is demonstrated over the Saguenay-Lac-Saint-Jean region (13 200 km2) of Quebec (Canada). The PGR mapping process was based on a model incorporating water budget components. The vertical inflows (VI) include water amounts from rainfall and snowmelt, whereby the latter was assessed using HYDROTEL model. VI were combined with the maximum and minimum temperatures to estimate actual evapotranspiration (AET), while the surface runoff (RuS) was assessed using the curve number method. Field observations of annual variation in temperatures and the water budget components, over a period of 100 years (1910–2009), were used to provide a comprehensive overview of the effects of climate change on PGR. The last 10 years of the observation period (i.e., 2000–2009) indicate that 6% of the study area has PGR rates of 35%–50%. PGR rates of 20%–35% occur in 58% of the study area, while 36% have PGR of 5%–20%. The trend analysis of temperature time series reveals an average of 1.1 ± 0.6°C increase over 100 years. Also, an increase in the water budget components is observed. Despite the increasing trends of RuS and AET, PGR still showed an increasing trend with an average increase of 0.7 ± 0.4 mm/year over the past 100 years. This observation indicates that the increase in VI was enough to compensate for the increases in AET and RuS. This finding of an increasing PGR in the study area provides useful information for future studies focusing on predicting long-term PGR evolution and for the development of efficient long-term groundwater management strategies
Comparing time-Lapse PhenoCams with satellite observations across the Boreal forest of Quebec, Canada
Get PDFIntercomparison of satellite-derived vegetation phenology is scarce in remote locations because of the limited coverage area and low temporal resolution of field observations. By their reliable near-ground observations and high-frequency data collection, PhenoCams can be a robust tool for intercomparison of land surface phenology derived from satellites. This study aims to investigate the transition dates of black spruce (Picea mariana (Mill.) B.S.P.) phenology by comparing fortnightly the MODIS normalized difference vegetation index (NDVI) and the enhanced vegetation index (EVI) extracted using the Google Earth Engine (GEE) platform with the daily PhenoCam-based green chromatic coordinate (GCC) index. Data were collected from 2016 to 2019 by PhenoCams installed in six mature stands along a latitudinal gradient of the boreal forests of Quebec, Canada. All time series were fitted by double-logistic functions, and the estimated parameters were compared between NDVI, EVI, and GCC. The onset of GCC occurred in the second week of May, whereas the ending of GCC occurred in the last week of September. We demonstrated that GCC was more correlated with EVI (R2 from 0.66 to 0.85) than NDVI (R2 from 0.52 to 0.68). In addition, the onset and ending of phenology were shown to differ by 3.5 and 5.4 days between EVI and GCC, respectively. Larger differences were detected between NDVI and GCC, 17.05 and 26.89 days for the onset and ending, respectively. EVI showed better estimations of the phenological dates than NDVI. This better performance is explained by the higher spectral sensitivity of EVI for multiple canopy leaf layers due to the presence of an additional blue band and an optimized soil factor value. Our study demonstrates that the phenological observations derived from PhenoCam are comparable with the EVI index. We conclude that EVI is more suitable than NDVI to assess phenology in evergreen species of the northern boreal region, where PhenoCam data are not available. The EVI index could be used as a reliable proxy of GCC for monitoring evergreen species phenology in areas with reduced access, or where repeated data collection from remote areas are logistically difficult due to the extreme weather