Groundwater flow within overburden strata under dynamic stress conditions, Sydney Basin

Katarina David

Supervisors: Dr WendyTimms, Professor Andy Baker and Dr Rudra Mitra

There is currently a gap in the understanding of groundwater behaviour in dynamic stress environments and the role of low permeability rock strata as a barrier to vertical flow towards underground mining operations. This research focuses on quantifying vertical and horizontal components of groundwater seepage at the interface of high and low permeability rock strata within the constrained zone overlying a longwall coal mine. The hydrogeological and geomechanical behaviour of low permeability sedimentary strata with varying saturation conditions, and dynamic stress (eg. loading at large strains induced by subsidence) will be determined. Importantly, the theoretical decrease in hydraulic conductivity as pores become unsaturated will be evaluated to better understand the effectiveness of rock strata barriers to vertical flow.  

Multidisciplinary approaches (hydrogeology, geomechanics, hydrogeochemistry) will be used to evaluate site data, rock and water samples and to design experimental work. Data includes groundwater pore pressure data, wireline logging data, stress and strain analysis, mineralogy data from iTRAX rock core scanning, and analysis of groundwater chemistry  and major ion and isotope data from water samples. In addition, a new technique is adding value to drill core analysis by direct, high resolution analysis of naturally occurring stable oxygen-18 and hydrogen-2 (deuterium) isotopes in pore water.

The data will ultimately be used in the development of hydro and mechanical models to test several hypotheses for groundwater flow within overburden strata of the Southern Coalfield of the Sydney Basin.