Abstract

A study site located in a quarry on the Lincolnshire Limestone has been selected to examine the validity of the ‘dual porosity’ hypothesis and its application in models for the prediction of solute migration. An integrated approach has been adopted for the experimental programme, combining data obtained from both field and laboratory-scale investigations with mathematical modelling. The results of the first to stages of the experimental developments at the site are reported and the results are discussed in relation to he development of a full tracer test programme.

Fracture mapping has been conducted on the face and the floor of the quarry where the vertical fractures are seen to be discontinuous over depth. However, extensive horizontal bedding plane fissures are readily identifiable in the boreholes and represent the main paths for lateral flows. An extensive data collection programme has been conducted to characterize the hydraulic properties of these fissures, as well as the adjacent altered and unaltered matrix. Important results for future tracer testing were obtained from the hydraulic tests which suggest the strong possibility of non-Darcian flow in the fissures under pumping and tracer test conditions and the probability of strong spreading of solutes at injection wells under forced inflows. Preliminary tracer tests confirm the difficulty of employing laboratory defined diffusion coefficients as input data to ‘dual porosity’ models of local-scale transport.

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