Infiltration, hydrogeology, and heterogeneity - Management of pressure and flow: A case study for the Varberg tunnel project

University essay from Göteborgs universitet/Institutionen för geovetenskaper

Abstract: This thesis aims to describe a conceptual model of the sedimentology for Swedish (or nordic)conditions of heterogeneous aquifers but focus is on a case study in Varberg. This to facilitatethe identification of main water-bearing units (e.g. upper and lower aquifers, two-dimensionaland one-dimensional flow) by short duration hydraulic tests evaluated by the Hvorslev method.The purpose was to provide guidance in relation to location and design of mitigation measurefor the mitigation of pressure and flow focusing on infiltration and pumping. The analysisassumes that the geometric mean (median) of the saturated hydraulic conductivity in alognormal isotropic two-dimensional medium (aquifer) is the exact upscaled hydraulicconductivity (effective hydraulic conductivity) (Gupta, Rudra, Parkin, & Parkin, 2006; Renard,Le Loc'h, Ledoux, De Marsily, & Mackay, 2000). Based on this assumption the medianhydraulic conductivity from short duration hydraulic tests was compared to the effectivehydraulic conductivity obtained from transient (time-dependent) pumping test to explainaquifer heterogeneity and spatial variability in hydraulic conductivity. The conceptual model,in combination with short duration hydraulic tests, was found to be a valuable tool fordescribing the spatial distribution of measured hydraulic conductivities. Deviation of medianvalues of short duration hydraulic tests from hydraulic conductivity obtained from pumping testcould be described by the spatial variability (aquifer heterogeneity) of hydraulic conductivity.The flow pattern in the aquifers in Varberg generally seem to be disturbed by channel flows instructures or geological materials with high hydraulic conductivity (glaciofluvial) that createdeviation from a two-dimensional isotropic aquifer. The location and design of infiltration issuggested to depend on the spatial variability of hydraulic conductivity and these onedimensionalchannel flows.

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