Engineering and Environmental Geology Laboratory

Riparian areas are often considered important ecological ecotones that decrease the nitrate load of groundwater discharging into rivers. In this paper, the effectiveness of nitrogen removal from groundwater in a riparian area has been evaluated. We used a quantitative ...

Thanks to a sophisticated transient hydrogeological modelling allowing the determination of the pore pressure fields in La Frasse landslide mass during a crisis, it has been possible to model the mechanical behaviour of the slide and obtain results that prove to be similar to ...

La vallée alpine de la Haute-Sarine est à plus d'un titre représentative des aquifères alluviaux de montagne, de par son environnement comme ses carac-téristiques hydrogéologiques. Les investigations et les analyses réalisées dans le cadre de cette étude nous ont permis d' ...

In this paper we present two enhanced variants of the smoothed particle hydrodynamics (SPH) method for the numerical simulation of free surface flows of viscous fluids. Improvements are achieved by deriving a new set of general discrete SPH-like equations under an energy-based framework and applying a corrected (high-order) or coupled particle approximation scheme for function derivatives. By doing so, we ensure that the enhanced variants retain the conservative nature of SPH which is important for the stability of long-term simulations. Among various corrected approximations, we here implement the one obtained by the so-called finite particle method (FPM) within the framework to produce a higher-order SPH method which conserves both linear and angular momentums. In order to improve the efficiency of the higher-order variant, a coupled approach with the idea of using the SPH approximation for the interior particles and the FPM approximation for the exterior particles is also proposed and tested in this paper. Three prototype tests concerning free deformation of a viscous fluid patch with free surface are presented with comparisons between different methods to demonstrate the performance of the two proposed methods. Numerical results show that both the higher-order version using FPM and the coupled version using FPM/SPH outperform the original version of SPH in respect of accuracy and stability.

Vertical growth of cities into the ground is still to be developed, in particular for transport, storage of goods and geothermal exploitation. This article presents a synthesis of the potential resources offered by the urban underground and some experiences derived from ...

Vertical growth of cities into the ground is still to be developed, in particular for transport, storage of goods and geothermal exploitation. This article presents a synthesis of the potential resources offered by the urban underground and some experiences derived from different cities around the world. Analysis of these experiences shows that these resources have often been developed without any real long-term planning. This synthesis proposes a more complete approach to underground resource management, insisting on the compatibilities or incompatibilities of a parallel exploitation of certain resources due to their interactions (e.g. geothermics-groundwater). Since the impact of most underground work goes far beyond the space occupied, it must be conceived on the city scale. To attain this objective, the authors propose the notion of three-dimensional land planning for urban territory. This new concept goes much farther than the GIS applications used for the "cadastre" in the first metres of underground. A new way of conceiving underground management for the long-term development of the city is recommended. Résumé: La croissance verticale des villes vers le bas reste à développer, notamment pour le transport, le stockage de biens et l'exploitation géothermique. Le présent article fait une synthèse du potentiel de ressources que représente le sous-sol urbain et des expériences faites dans différentes métropoles. L'analyse de ces expériences montre que ces ressources ont souvent été mises en valeur de manière non systématique et non planifiée à long terme. Cette synthèse développe une approche plus complète de la gestion des ressources du sous-sol, en insistant sur les compatibilités ou non compatibilités de l'exploitation en parallèle de certaines ressources. en raison de leurs interactions (par exemple géothermie-eaux souterraines). En raison de l'impact des ouvrages bien au-delà de l'espace qu'ils occupent, ils doiventêtre conçus à l'échelle de la cité. Les auteurs présentent à cette fin le concept d'aménagement tridimensionnel du territoire urbain. Cette notion nouvelle va bien au-delà des systèmes d'information géographiques qui traitent du cadastre souterrain dans les premiers mètres du sous-sol. Une nouvelle manière de gérer le sous-sol est recommandée pour le développement à long terme de la ville.

Groundwater with underground residence times between days and a few years have been investigated over more than 20 years from 487 remote sites located in different aquifer types in the Alpine belt. Analysis of the data reveals that groundwaters evolved in crystalline, evaporite, carbonate, molasse, and flysch aquifers can be clearly distinguished based on their major and trace element composition and degree of mineralisation. A further subdivision can be made even within one aquifer type based on the trace element compositions, which are characteristic for the lithologic environment. Major and trace element concentrations can be quantitatively described by interaction of the groundwater with the aquifer-specific mineralogy along the flow path. Because all investigated sites show minimal anthropogenic influences, the observed concentration ranges represent the natural background concentrations and can thus serve as a "geo-reference" for recent groundwaters from these five

In spring, snowmelt releases huge quantities of meltwater, affecting the hydrology of Alpine areas. Seasonal soil frost influences these water fluxes by locally decreasing the infiltration capacity of the soil, resulting in an increased amount of surface runoff. The main goal of this study was to investigate the spatial variability of the seasonal frost depth and to quantify by how

In this paper we present a regularized Lagrangian finite point method (RLFPM) for the numerical simulation of incompressible viscous flows. A Lagrangian finite point scheme is applied to the projection method for the incompressible Navier-Stokes equations. The approximation of spatial derivatives is obtained by the weighted least squares method. The pressure Poisson equation with Neumann boundary condition is solved by a stabilized finite point method. A key aspect of the present approach is the periodic redistribution of the particle locations, which are being distorted by the flow. Again, weighted least squares approximation is implemented to interpolate the properties of the old particles onto the new particle locations. With the proposed regularization technique, problems associated with the flow-induced irregularity of particle distribution in the Lagrangian finite point scheme are circumvented. Three numerical examples, Taylor-Green flow, lid-driven flow in a cavity and flow through a periodic lattice of cylinders, are presented to validate the proposed methodology. The problem of extra diffusion caused by regularization is discussed. The results demonstrate that RLFPM is able to perform accurate and stable simulations of incompressible viscous flows.

Riparian areas are often considered important ecological ecotones that decrease the nitrate load of groundwater discharging into rivers. In this paper, the effectiveness of nitrogen removal from groundwater in a riparian area has been evaluated. We used a quantitative hydrogeological approach which delimited homogeneous stream tubes based on the water table contour. We constructed water and mass balances and used the results to estimate the mass of nitrogen removed by biological processes. Nitrogen removal effectiveness was calculated as the ratio of nitrogen removed to the total nitrogen mass flowing through the riparian area. This approach requires knowledge of the hydrogeological settings and coverage of an area larger than the study site. The removal we observed was seasonally variable, ranging between 2.2 and 7.6 mg N m 22 day 21, and represented up to 95% of the total nitrogen mass entering the riparian area in late summer. Removal effectiveness was only 27-38% in winter, due to the combination of a high nitrogen input and a low plant uptake. Nitrogen removal was highest in spring, but effectiveness was about 60% because the input was as high as in winter. Rainwater infiltrating the riparian area could represent almost the same quantity as groundwater input. Under such conditions, the dilution effect is very important in riparian areas that are not nitrate sources and it is essential to maintain this non-nitrate-emissive use. This study showed that the effectiveness of nitrogen removal in a riparian area is highly dependent on the pathway of water movement through its biologically active layers.

In spring, snowmelt releases huge quantities of meltwater, affecting the hydrology of Alpine areas. Seasonal soil frost influences these water fluxes by locally decreasing the infiltration capacity of the soil, resulting in an increased amount of surface runoff. The main goal of this study was to investigate the spatial variability of the seasonal frost depth and to quantify by how much this seasonal soil frost affects the snowmelt discharge. For this purpose, an extensive field study was run for two winter seasons (2000/2001 and 2001/2002) at Gd St Bernard (2470 m) and Hannigalp (2090 m) in the southern Swiss Alps. The different components of the water balance (lateral runoff, deep percolation, liquid soil water content) were measured on delimited plots of 5 m 2. The two winters investigated had opposing weather and soil frost conditions: in the first winter a thick snowpack prevented the formation of soil frost, whereas in the second winter little snow fell until January, which produced a deep and persistent soil frost. We classified the snowmelt events into several classes (mid-winter, late winter, spring and postspring) and analysed the significance of the different water flow components for each melt situation. While 90-100% of melt water infiltrated into the ground during the first winter, 25-35% of melt water ran off laterally in the second, mainly during late winter and spring snowmelt events. In that second winter, the soil infiltration capacity was primarily reduced by the presence of a basal ice sheet after midwinter melt events.

Thanks to a sophisticated transient hydrogeological modelling allowing the determination of the pore pressure fields in La Frasse landslide mass during a crisis, it has been possible to model the mechanical behaviour of the slide and obtain results that prove to be similar to the monitored data, in terms of peak velocity, distribution of velocity with time and space and total displacements. Such results are reached only when appropriate constitutive modelling laws are used, and when geotechnical tests supply all the required parameters. The main results concern the potential effect of a drainage system during a crisis, like the one experienced in 1994. It can include vertical boreholes equipped with pumps or drains drilled from a gallery. The draining system reduces horizontal displacements down to 5% of the values modelled during the crisis. This effect, which appears to extend over a large width, will be even more significant if the boreholes discharge the drained water into the gallery, due to its extension in the presently stabilised landslide mass below the active zone. The modelling tools developed for La Frasse landslide thus provide all the necessary information to optimise the drainage scheme.

Four underground resources have been seen as having long-term potential to support sustainable urban development: underground space, groundwater, geomaterials and geothermal energy. Utilization of these resources proposes a new paradigm of economic development: underground urbanism. The new management approach named "Deep City Method" is put forward to aid decisionmakers to integrate global potential of the urban underground into city-scale strategic planning. The research output will be presented in form of two papers each with a different focus. Part 1 aims to introduce the concept, process and initial application in Switzerland; Part 2 is devoted to show methodological insight for a new zoning policy in China and investment scenarios for project cost viability. The Part 2 paper will demonstrate a comprehensive evaluation methodology for underground resources beneath the municipality of Suzhou in China, in order to formulate 3D land zoning. Strategic districts in Suzhou city of China are selected for feasibility outlook and policy instrument proposition. Finally, a new economic index "Underground cost efficiency premium" has been proposed to aid project developers to justify competitiveness of underground development.

A discrete reduced distance method to generate 2-D and 3-D granular porous media is presented. The main property of the method is to produce heterogeneous and/or anisotropic packed beds of joined grains with arbitrary shapes and optimum fitting (i.e., minimum porosity). The iterative generation process starts with the coarsest grain and adjusts the size and location of the next ones depending on the updated available space. Hence, grain size distribution cannot be specified directly but is merely the consequence of user defined input parameters. The latter consists of a set of randomly distributed initial points, a few typical predefined grain shapes as well as the minimum and maximum grain diameters. The simulated granular media can readily be processed by an appropriate mesh generator to allow for subsequent numerical solutions of differential equations.

ÐSince water is the main contamination arrow in the underground, it is necessary to get good indicators to be able to detect pollution sources as old wastes dump. This is also useful for the monitoring of contaminated sites in time and space. The new analytical method high resolution-ICP-MS is an opportunity to improve the characterization of water by analyzing mineral traces at very low level (<0.1 mg/l). Numerous site descriptions (41 sites) and statistical approach of collected samples (223 samples), have shown that the use of the inorganic trace elements is helpful for the detection and/ or the survey of contaminated sites. Another interesting result shows speci®c indicators for hazardous waste. This method can be used beside organic compound analyses, which are heavier and expensive in practice.

ÐSince water is the main contamination arrow in the underground, it is necessary to get good indicators to be able to detect pollution sources as old wastes dump. This is also useful for the monitoring of contaminated sites in time and space. The new analytical method high resolution-ICP-MS is an opportunity to improve the characterization of water by analyzing mineral traces at very low level (<0.1 mg/l). Numerous site descriptions (41 sites) and statistical approach of collected samples (223 samples), have shown that the use of the inorganic trace elements is helpful for the detection and/ or the survey of contaminated sites. Another interesting result shows speci®c indicators for hazardous waste. This method can be used beside organic compound analyses, which are heavier and expensive in practice.