Underground » Strata Control and Windblasts
In underground mines the mining induced permeability change in the overburden is the single most important factor that impacts water and gas flow. Empirical estimates of mining induced permeability change are inaccurate. This project aimed to quantify the permeability change resulting from longwall mining by fully utilising mine specific geology and hydrogeology. Researchers numerically simulated fluid flow through the fracture network that results from applying the fracture modelling technique developed in previous research. Measuring pressure drops and flow rates through the fracture network allows permeability changes to be quantified at all points in the overburden.
The main objectives of this project were to:
- Estimate overburden permeability changes by numerically simulating fluid flow through the porous, fractured rock. The location, connectivity and size of the mining induced fractures will be predicted using the fracture-modelling technique developed in the earlier project C24020 and stage one of this project.
- Promote uptake of by the publication of a robust set of modelling procedures and FISH subroutines that have been tested on 5 mine sites; and further refine the methodology developed in both C24020 and stage 1 of this project.
In stage 1, published December 2020, the broad completed objectives were to:
- Expand the science base and understanding of strata caving mechanics during longwall mining and specifically focus on the fracturing processes in coal measure rocks;
- Extend the technique developed in project C24020 of initiating and propagating fractures, estimating fracture aperture and connectedness and thereby calculating the permeability of a rockmass from first principle; and to
- Quantify the height of complete groundwater drainage above longwall panels from studies of three different mining environments.
Issues encountered and outcomes of both stages are described in the stage 2 report.
Stages 1 and 2 are now published together.