Simulation of rock salt dissolution and its impact on land subsidence

Extensive land subsidence can occur due to subsurface dissolution of evaporites such as halite and gypsum. This paper explores techniques to simulate the salt dissolution forming an intrastratal karst, which is embedded in a sequence of carbonates, marls, anhydrite and gypsum. A numerical model is developed to simulate laminar flow in a subhorizontal void, which corresponds to an opening intrastratal karst. The numerical model is based on the laminar steady-state Stokes flow equation, and the advection dispersion transport equation coupled with the dissolution equation. The flow equation is solved using the nonconforming Crouzeix-Raviart (CR) finite element approximation for the Stokes equation. For the transport equation, a combination between discontinuous Galerkin method and multipoint flux approximation method is proposed. The numerical effect of the dissolution is considered by using a dynamic mesh variation that increases the size of the mesh based on the amount of dissolved salt. The numerical method is applied to a 2D geological cross section representing a Horst and Graben structure in the Tabular Jura of northwestern Switzerland. The model simulates salt dissolution within the geological section and predicts the amount of vertical dissolution as an indicator of potential subsidence that could occur. Simulation results showed that the highest dissolution amount is observed near the normal fault zones, and, therefore, the highest subsidence rates are expected above normal fault zones

Integrated methods and scenario development for urban groundwater management and protection during tunnel road construction: a case study of urban hydrogeology in the city of Basel, Switzerland

In the northwestern area of Basel, Switzerland, a tunnel highway connects the French highway A35 (Mulhouse-Basel) with the Swiss A2 (Basel-Gotthard-Milano). The subsurface highway construction was associated with significant impacts on the urban groundwater system. Parts of this area were formerly contaminated by industrial wastes, and groundwater resources are extensively used by industry. During some construction phases, considerable groundwater drawdown was necessary, leading to major changes in the groundwater flow regime. Sufficient groundwater supply for industrial users and possible groundwater pollution due to interactions with contaminated areas had to be taken into account. A groundwater management system is presented, comprising extensive groundwater monitoring, high-resolution numerical groundwater modeling, and the development and evaluation of different scenarios. This integrated approach facilitated the evaluation of the sum of impacts, and their interaction in time and space with changing hydrological boundary conditions. For all project phases, changes of the groundwater system had to be evaluated in terms of the various goals and requirements. Although the results of this study are case-specific, the overall conceptual approach and methodologies applied may be directly transferred to other urban area

Comparison of light transmission and reflection techniques to determine concentrations in flow tank experiments

Transmissive and reflective intensity measurements for visual concentration determinations in 2D flow tank experiments were compared and evaluated for their applicability in the study of flow and transport phenomena. A density-dependent heterogeneous flow experiment was conducted and transmission and reflection images of the dyed saltwater plume were analyzed. A single light source and dark curtains forced the light to pass through the porous media only, thus facilitating the transmission measurements. The reflection images delivered a more homogeneous spatial illumination than the transmission images. Major perturbations of the transmission images were lens flare effects and light dispersion within the bead-water-Plexiglas system which smear the front of the plume. Based on the conducted evaluation of transmissive and reflective intensity measurements, the reflection data delivered more reliable intensity values to derive solute concentrations in intermediate scale flow tank experiment

Adaptives Grundwassermanagement in urbanen Gebieten: Einfluss der Oberflächengewässer-Grundwasser-Interaktion am Beispiel künstlicher Grundwasseranreicherung sowie variabler In-/Exfiltration der Birs (Schweiz)

Zusammenfassung: Der Nutzungsdruck auf Grundwasserressourcen in intensiv genutzten Flussebenen wird zunehmend größer. Ziel dieses Beitrages ist, anhand eines repräsentativen, instationären Datensatzes eines urbanen Grundwassersystems (Unteres Birstal CH) aufzuzeigen, wie mit Ansätzen des adaptiven Grundwassermanagements die Voraussetzungen für die nachhaltige Nutzung von Grundwasserressourcen geschaffen werden können. Mithilfe eines instationären Grundwassermodells können spezifische Fragen der Fluss-Grundwasser-Interaktion und dem Betrieb künstlicher Grundwasseranreicherung beantwortet werden. Die Instationarität der Fluss-Grundwasser-Interaktion und eine damit zusammenhängende Änderung von In - und Exfiltrationsverhältnissen konnte für verschiedene Flussabschnitte ermittelt werden. Die Datenauswertung eines Jahrhunderthochwassers trug wesentlich zum Verständnis dieser Prozesse bei. Durch ein Experiment mit der längerfristigen Außerbetriebnahme einer künstlichen Grundwasseranreicherung im Untersuchungsgebiet konnten die Auswirkungen von geplanten Nutzungsänderungen abgeschätzt werden. Die Untersuchungen tragen zum Prozessverständnis des Grundwassersystems bei und liefern die Grundlage für eine Diskussion über lang-, mittel- und kurzfristige Ziele hinsichtlich der regionalen Bewirtschaftung urbaner Wasserressource

Groundwater, geothermal modelling and monitoring at city-scale : reviewing European practice and knowledge exchange : TU1206 COST sub-urban WG2 report

The need for cities to make more effective use of the subsurface on which they stand, is increasingly being recognised in Europe and further afield to be essential for future cities to be sustainable and more resilient [1,2]. However, city planning worldwide remains largely 2D, with very few cities having any substantial subsurface planning or Masterplans – the cities of Helsinki, Montreal, Singapore being rare exceptions [3,4]. The consequences of inadequate consideration and planning of the subsurface are far-reaching, in economic, environmental and social terms. Across Europe, poor understanding of ground conditions is recognised as the largest single cause of construction project delay and overspends [5]. Management of urban groundwater and shallow geothermal energy resources is becoming increasingly important as cities are increasingly looking to use these resources to meet current and future energy and heating and water needs. Whilst these are, alongside potential underground building space, the two most important resources for future cities, the monitoring and regulation of these resource is widely variable across Europe. For subsurface opportunities such as groundwater and geothermal energy to be realised and utilised to greatest effect to support growing city populations and infrastructure, city planners must be both aware of, and have some understanding of the resources, available data and research, and both the opportunities and risks which the resources provide to city development [6,7]. To supply this understanding to city municipalities and others, geological surveys must have robust datasets of groundwater and geothermal resources at city-scale, and the relevant knowledge and understanding from these data must be made accessible to inform subsurface planning in appropriate datasets relevant to different scale of interest in different planning stages. What density and frequency of data are required for a robust understanding of a city’s groundwater and geothermal resources will be different in different cities, according to the complexity of the resources, and the intensity of subsurface use and demands on the resources. Indeed, no one design of city-scale monitoring or modelling of ground-water and -heat resources is appropriate for all cities, or for all monitoring objectives. However, the guiding principles of good practice for developing robust city-scale monitoring, and datasets are widely applicable, as are the key principles for ensuring these data inform city planning processes. This report provides an initial review of existing examples of current practices in Europe with respect to groundwater and geothermal monitoring and modelling, as a resource for other cities to learn from and build upon. The report also provides an overview of some of the different practices used for communicating groundwater and geothermal energy data and knowledge to inform urban planning and managemen

Spatio-temporal Models of Lymphangiogenesis in Wound Healing

Several studies suggest that one possible cause of impaired wound healing is failed or insufficient lymphangiogenesis, that is the formation of new lymphatic capillaries. Although many mathematical models have been developed to describe the formation of blood capillaries (angiogenesis), very few have been proposed for the regeneration of the lymphatic network. Lymphangiogenesis is a markedly different process from angiogenesis, occurring at different times and in response to different chemical stimuli. Two main hypotheses have been proposed: 1) lymphatic capillaries sprout from existing interrupted ones at the edge of the wound in analogy to the blood angiogenesis case; 2) lymphatic endothelial cells first pool in the wound region following the lymph flow and then, once sufficiently populated, start to form a network. Here we present two PDE models describing lymphangiogenesis according to these two different hypotheses. Further, we include the effect of advection due to interstitial flow and lymph flow coming from open capillaries. The variables represent different cell densities and growth factor concentrations, and where possible the parameters are estimated from biological data. The models are then solved numerically and the results are compared with the available biological literature.Comment: 29 pages, 9 Figures, 6 Tables (39 figure files in total