Groundwater characterization of a heterogeneous granitic rock massif for shallow tunneling

Shallow tunneling may encounter a number of problems, the most important of which is high water inflows in transmissive areas that are often associated with fractures or discontinuities. Moreover, research into shallow tunneling may be limited by the duration and cost of the civil engineering works. Two important aspects that are often overlooked are: variable groundwater behavior of faults (conduit, barrier, conduit-barrier), and role of groundwater connectivity between fractures that cross the tunnel and the rest of the rock massif. These two aspects should be taken into account in the geological and groundwater characterization to correct the tunnel design and minimize hazards. A geological study and a preliminary hydrogeological characterization (including a prior steady state investigation and cross bore-hole tests) were carried out in a granitic sector during the construction of Line 9 of the Barcelona subway (B-20 area). The hydrogeological conceptual model was constructed using a quasi-3D numerical model, and different scenarios were calibrated. Faults and dikes show a conduit-barrier behavior, which partially compartmentalized the groundwater flow. The barrier behavior, which is the most marked effect, is more prominent in faults, whereas conduit behavior is more notable in dikes. The characterization of groundwater media entailed a dewatering plan and changes in the tunnel course. This enabled us to construct the tunnel without any problems

Recent and old groundwater in the Niebla-Posadas regional aquifer (southern Spain): Implications for its management

The Niebla-Posadas (NP) aquifer in southern Spain is one of the main groundwater sources for the lower Guadalquivir Valley, a semiarid region supporting an important population, agriculture and industry. To contribute to the understanding of this aquifer the assessment of sustainable use of groundwater, the residence time of groundwater in the NP aquifer has been estimated using 3H, 14C and 36Cl. Along the flow paths, recharged groundwater mixes with NaCl-type waters and undergoes calcite dissolution and is further modified by cation exchange (Ca Na). Consequently, the water loses most of its calcium and the residual d13CDIC in the groundwater is isotopically enriched. Further modifications take place along the flow path in deeper zones, where depleted d13CDIC values are overprinted due to SO42 and iron oxide reduction, triggered by the presence of organic matter. Dating with 3H, 14C and 36Cl has allowed the differentiation of several zones: recharge zone (30 ky). An apparent link between the tectonic structure and the groundwater residence time zonation can be established. Regional faults clearly separates deep zone 1 from the distinctly older age (>30 ky) deep zone 2. From the estimated residence times, two groundwater areas of different behavior can be differentiated within the aquifer

La modelización tridimensional del flujo del agua subterránea y transporte de calor en la gestión de recursos geotérmicos someros en zonas urbanas

La planificación del uso geotérmico del agua subterránea en acuíferos someros urbanos requiere un modelo numérico capaz de reproducir los efectos de la explotación actual y ser capaz de predecir los impactos derivados de dicha actividad. En este trabajo se presenta el desarrollo preliminar de un modelo numérico que puede contribuir a mejorar la gestión de los recursos geotérmicos someros en la ciudad de Zaragoza. El modelo numérico permite implementar toda la información hidrogeológica y térmica recopilada, explicar esta información de forma coherente reproduciendo la física de fluidos y termodinámica en medios poroso s y predecir a medio y largo plazo los impactos producidos. Finalmente se muestran las posibilidades y ventajas derivadas del uso del modelo numérico en la gestión de permisos de concesión de derechos de explotación para nuevos aprovechamientos. The management of the thermal use of groundwater in shallow urban aquifers requires a numerical model capable of reproducing the impacts of actual exploitations and of predicting further impacts in the future. In this work, the numerical model developed for the management of shallow geothermal resources in the city of Zaragoza (Spain) is presented. The model allows to explain the data coherent with the fluid physics and the heat transport in porous media and also provide predictions for the thermal impacts at mid- and long-term. Finally, the possibilities and advantages derived from the use of the numerical modelling for the concession process of new exploitation licenses are described

Fenómenos de inundación subterránea asociados a las crecidas del río Ebro en la ciudad de Zaragoza

En este trabajo se estudia desde un punto de vista cuantitativo la respuesta hidráulica del acuífero aluvial urbano de Zaragoza a las crecidas del río Ebro con el objetivo del estudio de fenómenos de inundación subterránea. La simulación de dicha respuesta mediante un modelo numérico de flujo ha hecho posible evaluar la interacción del nivel freático con las estructuras subterráneas próximas al río Ebro. Los resultados obtenidos han sido validados con afecciones documentadas demostrando la utilidad del modelo.Además, de estos resultados se desprende que un total de 107 edificios son susceptibles de interaccionar con el agua subterránea donde las estructuras pueden llegar a ser sometidas a presiones hidrostáticas de hasta 0,7 kg·cm-2 dependiendo de la profundidad de la estructura y de la crecida considerada. The objective of this work is to study groundwater inundation phenomena in the metropolitan area of Zaragoza as a consequence of Ebro river flood events. A groundwater flow numerical model has been used to simulate the hydraulic response of the urban groundwater body to flood events in order to quantify the groundwater-building basements interaction. The model developed has been validated with damage documented proving its utility. The results showed that 107 buildings are vulnerable to groundwater inundation and that the structures affected may experience a pressure load up to 0.7 kg·cm-2 depending on the structure depth and the flood event considered

Groundwater characterization of a heterogeneous granitic rock massif for shallow tunneling

Shallow tunneling may encounter a number of problems, the most important of which is high water inflows in transmissive areas that are often associated with fractures or discontinuities. Moreover, research into shallow tunneling may be limited by the duration and cost of the civil engineering works. Two important aspects that are often overlooked are: variable groundwater behavior of faults (conduit, barrier, conduit-barrier), and role of groundwater connectivity between fractures that cross the tunnel and the rest of the rock massif. These two aspects should be taken into account in the geological and groundwater characterization to correct the tunnel design and minimize hazards. A geological study and a preliminary hydrogeological characterization (including a prior steady state investigation and cross bore-hole tests) were carried out in a granitic sector during the construction of Line 9 of the Barcelona subway (B-20 area). The hydrogeological conceptual model was constructed using a quasi-3D numerical model, and different scenarios were calibrated. Faults and dikes show a conduit-barrier behavior, which partially compartmentalized the groundwater flow. The barrier behavior, which is the most marked effect, is more prominent in faults, whereas conduit behavior is more notable in dikes. The characterization of groundwater media entailed a dewatering plan and changes in the tunnel course. This enabled us to construct the tunnel without any problems

Superação da dormência em sementes de mutamba (guazuma ulmifolia lam. - sterculiaceae)

A Guazuma ulmifolia Lam. possui sementes com acentuada impermeabilidade a água, o que dificulta sua germinação. Avaliou-se o efeito do período de imersão das sementes em ácido sulfúrico (0, 4, 8, 12 e 16 min) e em água a 60 ºC por 0, 4, 8, 12 e 16 min, na emergência de plântulas, início da emergência e índice de velocidade de emergência. O experimento foi realizado em Laboratório de Biologia, em delineamento inteiramente casualizado em fatorial 2 (tratamento pré-germinativo) x 5 (períodos de imersão), com três repetições de 20 sementes. O precondicionamento das sementes em ácido sulfúrico como em água mostrou-se eficiente na superação da dormência dessa espécie, promovendo aumento na porcentagem de emergência de plântulas e velocidade de emergência e redução no tempo para o início da germinação. A eficiência do tratamento químico com ácido sulfúrico foi obtida com um tempo de imersão de 8 min, enquanto no tratamento físico com água a 60 ºC a eficiência foi obtida com o tempo de imersão de 16 min