Connecting the dots: Fracture mapping for landfill sites in fractured bedrock”

A landfill constructed in fractured bedrock can pose a potential risk of contaminant leachate to the surroundings through fractures and/or fracture networks. Therefore, adequate understanding of factures and fracture networks is a key element for constructing environmentally safe, sustainable and long-term landfills in fractured bedrocks. Mapping of geological features especially fracture networks provides essential data to establish a fundamental understanding of the local geology and hydrogeology of such landfill sites.

The objective of this study to develop  a 3D model of fractures and fracture networks, surrounding a quarry in southwestern Norway, Rekefjord. The test site, selected as a potential landfill site, consists of  moderately fractured crystalline monzonorite near the shoreline. Eight previously drilled and logged observation boreholes (NGI) on the crest surrounding the open pit were analysed. Results of subsurface fracture mapping from well logs show that orientations of natural fractures are scattered and mostly appear to be open. The Terzaghi correction shows there could be more steeply dipping fractures, these are not well captured through vertical borehole logging. Additional field work consisted of drone scanning of the interior of the whole quarry and specific locations to generate a virtual 3D model. This 3D model is used to conduct fracture measurements using the LIME software. The fracture data extracted from the 3D model will be used to assess the correlation and consistency in fracture orientation between the internal rock face and borehole measurements. The geometry of fracture networks and individual fractures can have significant impact on flow through fractured rock. 

Results will also be used to constrain a numerical groundwater flow model to improve understanding of potential pathways of contaminants from the landfill to the surroundings. The results of this research will improve assessment methodology and criteria for new landfill sites in fractured bedrock.