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

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 facilitate the identification of main water-bearing units (e.g. upper and lower aquifers, two-dimensional and 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 measure for the mitigation of pressure and flow focusing on infiltration and pumping. The analysis assumes that the geometric mean (median) of the saturated hydraulic conductivity in a lognormal isotropic two-dimensional medium (aquifer) is the exact upscaled hydraulic conductivity (effective hydraulic conductivity) (Gupta, Rudra, Parkin, & Parkin, 2006; Renard, Le Loc'h, Ledoux, De Marsily, & Mackay, 2000). Based on this assumption the median hydraulic conductivity from short duration hydraulic tests was compared to the effective hydraulic conductivity obtained from transient (time-dependent) pumping test to explain aquifer heterogeneity and spatial variability in hydraulic conductivity. The conceptual model, in combination with short duration hydraulic tests, was found to be a valuable tool for describing the spatial distribution of measured hydraulic conductivities. Deviation of median values of short duration hydraulic tests from hydraulic conductivity obtained from pumping test could 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 in structures or geological materials with high hydraulic conductivity (glaciofluvial) that create deviation from a two-dimensional isotropic aquifer. The location and design of infiltration is suggested to depend on the spatial variability of hydraulic conductivity and these onedimensional channel flows.