Application of numerical modelling to the comprehensive analysis of slope stability

Paper deals with the comprehensive methodology for the numerical simulation of potentially unstable slopes combining engineering geological, hydrological, hydrogeological and geotechnical computational model for the assessment of slope stability. Engineering geological model based on available survey data characterizes the rock environment using individual quasi-homogenous units. Model is defined on the basis of documented lithostratigraphic units in exploration probes and field relief documented by advanced methods, including satellite radar interferometry and laser surface scanning. On the basis of engineering geological model, the hydrological model using MIKE SHE software (Finite Difference Method) was performed. Hydrological model includes simulation of surface runoff, evapotranspiration and flow in unsaturated near-surface zone. The model was calibrated on the basis of available field data. Outputs from this model were used as input initial conditions of the following hydrogeological model. Software FEFLOW based on the Finite Element Method was subsequently used to the creation of hydrogeological model focused on the water flow and distribution of pore pressures of groundwater in individual quasi-homogeneous units in saturated zone. The infiltration condition determined by the hydrological model is considered and a flow model with variable saturation is applied. Finally, the geotechnical stability model of slope following the engineering geological, hydrological and hydrogeological models was performed. The occurrence of plastic and failure zones (assuming elastic-perfectly plastic Mohr-Coulomb constitutive model) inside the slope was simulated by using software MIDAS GTS NX based on the Finite Element Method. Stability factor SSRF (Shear Strength Reduction Factor) is evaluated based on the Shear Strength Reduction Method) as the ratio of actual shear strength and minimum shear strength required to maintain stability. Paper deals also with the comparison of stability factor of natural slope obtained from 3D and 2D numerical model. Generally, in the case of natural slope the condition of plane strain is not fulfil, 2D model is not realistic and 3D model is needed, especially in case of concave morphology of slope

Numerical simulation of heat recovery from asphalt pavement in Finnish climate conditions

A 3-dimensional mathematical model of asphalt pavement system was developed, based on the fundamental energy balance, to calculate temperatures beneath asphalt surface using hourly measured solar radiation, air temperature and wind velocity data. The modelling was conducted to predict the heat retention under the asphalt surface to seek an optimum position of pipe tubing to maximise the heat extraction considering the Nordic winter conditions for future infrastructure projects. The model results show good agreement with the experimental results conducted in a span of three months (June–Sept) notwithstanding the simplification of the model i.e. thermal properties unaffected by changing moisture content, perfect contact between different layers and homogeneous and isotropic thermal properties of materials (asphalt, sand and gravel). The findings indicated that the positioning of the heat extraction tubes under the asphalt layer will be dictated by the application. For heat extraction, pipes closer to the surface are ideal for maximal heat absorption during summer, however, in winter the outer temperature may effect properties the pipes. Parameters including pipe diameter, positioning of the pipes and flow rate were analysed. Temperature increase of up to 10 °C gain was observed for piping closer to the asphalt layer and 6 °C for pipes position at deeper from the asphalt layer. This model could be used in future to optimise critical variables for successful implementation of asphalt heating concepts.© 2023 The Author(s). Published by Elsevier Masson SAS. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).fi=vertaisarvioitu|en=peerReviewed

Application of numerical modelling to the comprehensive analysis of slope stability

Paper deals with the comprehensive methodology for the numerical simulation of potentially unstable slopes combining engineering geological, hydrological, hydrogeological and geotechnical computational model for the assessment of slope stability. Engineering geological model based on available survey data characterizes the rock environment using individual quasi-homogenous units. Model is defined on the basis of documented lithostratigraphic units in exploration probes and field relief documented by advanced methods, including satellite radar interferometry and laser surface scanning. On the basis of engineering geological model, the hydrological model using MIKE SHE software (Finite Difference Method) was performed. Hydrological model includes simulation of surface runoff, evapotranspiration and flow in unsaturated near-surface zone. The model was calibrated on the basis of available field data. Outputs from this model were used as input initial conditions of the following hydrogeological model. Software FEFLOW based on the Finite Element Method was subsequently used to the creation of hydrogeological model focused on the water flow and distribution of pore pressures of groundwater in individual quasi-homogeneous units in saturated zone. The infiltration condition determined by the hydrological model is considered and a flow model with variable saturation is applied. Finally, the geotechnical stability model of slope following the engineering geological, hydrological and hydrogeological models was performed. The occurrence of plastic and failure zones (assuming elastic-perfectly plastic Mohr-Coulomb constitutive model) inside the slope was simulated by using software MIDAS GTS NX based on the Finite Element Method. Stability factor SSRF (Shear Strength Reduction Factor) is evaluated based on the Shear Strength Reduction Method) as the ratio of actual shear strength and minimum shear strength required to maintain stability. Paper deals also with the comparison of stability factor of natural slope obtained from 3D and 2D numerical model. Generally, in the case of natural slope the condition of plane strain is not fulfil, 2D model is not realistic and 3D model is needed, especially in case of concave morphology of slope

Numerical modelling as a tool for optimisation of ground water exploitation in urban and industrial areas

<p>The paper presents an approach to flow and transport modelling, which has been an important tool for the development of protection options for the important groundwater resource of the City of Ostrava in the Czech Republic. The resource is threatened by the impacts of long-term contaminant releases from a number of industrial enterprises in its neighbourhood. Due to the complex hydrogeological settings and man-made impacts, effective protection of the Nova Ves groundwater resource requires careful co-ordination of mitigation measures at individual sites. It was proved that long-term pumping intensity (140 l/s) does not guarantee protection of the water quality. A reduction in the pumped discharge to 120 l/s was recommended. To ensure the long-term water quality in the water withdrawal area without any restriction on pumping discharge, a reduction in ammonium in the vadose zone by the 50 % would be required. However, so far, no remediation activities have been started. </p&gt

Sustainable Water Management in Iraq (Kurdistan) as a Challenge for Governmental Responsibility

<p>During the last few decades, a critical scarcity of water has occurred in the Middle East due to climate change and the mismanagement of water resources. The situation is complicated by the absence of an effective legislative framework at the local level as well as by the incapability and disrepute of the local water authorities. Most Iraqi citizens depend on the surface waters of the Tigris and Euphrates rivers, which have their sources in upstream neighbouring countries. Water crises concerning the shared waters urgently require a solution at the international level. Unfortunately, Iraq has faced several wars in a row (1980–2003), which has prevented the country from establishing its institutions. The rapid increase in the population of the transboundary countries on the Tigris and Euphrates rivers, and the high demands on agriculture, are accelerating water exploitation. In this paper, the present state of water management in Iraq from the viewpoint of the legislative framework, water balance, and transboundary issues will be discussed, with special attention to Kurdistan. Many legislative documents have been established or amended by the Iraqi and Kurdistan parliaments since 2003. In 2015, the Kurdistan Government Ministry of Agriculture and Water Resources, in cooperation with the EU, issued a guide for environmental legislation related to all environmental components such as air, water, and soil. The recommendations on actions needed in the water management in Kurdistan will be presented; they are inspired by the Water Framework Directive (WFD) (2000/60/EC) implemented in EU member states.</p&gt

Geochemical Modeling of Changes in Storage Rock Environments at CO₂ Injection Sites

Geochemical modeling in TOUGHREACT code was used to simulate chemical processes in CO2–rock–brackish water systems in a pilot research environment of CO2 storage in the Brodske area (Czech Republic). Models studied mineralogical changes in rock samples resulting from acidification of the aqueous phase caused by the dissolution of pressurized supercritical CO2. Rock samples of the reservoir horizon and cement from the grouting of an injection borehole were considered, and the water phase represented the mineralized groundwater. The aim of the study was to characterize the influence of CO2 in the geological structure on mineralogical rock changes and to predict gas distribution through the rocks bearing brackish water. The most important chemical processes are dissolution of carbonates and clay minerals during the injection of CO2 into the structure, as the increase in porosity in the structure affects the sequestration capacity of the reservoir rock. In the CO2–cement–brackish water system, the models confirm the rapid dissolution of portlandite and its replacement with calcite. The CSH gel is also dissolved, and silica gel appears. The porosity of the cement decreases. Further studies on such a cement slurry are needed to prevent the possibility of mechanical damage to the integrity of the borehole

Application of the Hybrid Finite Element Mixing Cell method to an abandoned coalfield in Belgium

The Hybrid Finite Element Mixing Cell (HFEMC) method is a flexible modelling technique particularly suited to mining problems. The principle of this method is to subdivide the modelled zone into several subdomains and to select a specific equation, ranging from the simple linear reservoir equation to the groundwater flow in porous media equation, to model groundwater flow in each subdomain. The model can be run in transient conditions, which makes it a useful tool for managing mine closure post-issues such as groundwater rebound and water inrushes. The application of the HFEMC method to an abandoned underground coal mine near the city of Liege (Belgium) is presented. The case study zone has been discretized taking advantage of the flexibility of the method. Then, the model has been calibrated in transient conditions based on both hydraulic head and water discharge rate observation and an uncertainty analysis has been performed. Finally, the calibrated model has been used to run several scenarios in order to assess the impacts of possible future phenomena on the hydraulic heads and the water discharge rates. Among others, the simulation of an intense rainfall event shows a quick and strong increase in hydraulic heads in some zones coupled with an increase in associated water discharge rates. This could lead to stability problems in local hill slopes. These predictions will help managing and predicting mine water problems in this complex mining system