School of Science, Engineering and Information Technology

Advancing the determination and numerical integration of shrink/swell characteristics for the prediction of subsidence and rebound of land

Project Title:

Advancing the determination and numerical integration of shrink/swell characteristics for the prediction of subsidence and rebound of land

Lead Supervisor:

Prof Thomas Baumgartl/GHERG

Supervisor(s):

Javad Yaghoubi/GHERG

Contact person and email address: Thomas Baumgartl; t.baumgartl@federation.edu.au

Description of the project:

Rehabilitation of the Latrobe Valley open cut pits will eventually lead to a refilling of the mine voids with water and advancing the natural process of a rise of the groundwater to levels similar to pre-mining. During the mining process, the aquifers had to be de-pressurised. Consequence of the lowering of the groundwater table was subsidence in the vicinity of the mine pit and following a cone of depression locally, but also affected land sub-regional. The depth of subsidence has been determined to up to 2m and partially even higher. Cause of subsidence is a combination of consolidation processes, but also shrinkage as a consequence of water loss. Re-pressurisation will lead to swelling process and upheave of subsided land. The extent of swelling will be a combination of the extent of drying achieved over time and during the previous de-pressurisation, the geomechanical properties of the individual geological strata affected by the desiccation and the overburden stresses.

The anticipated PhD project will investigate the swell/shrinkage behaviour not only from the point of view of water loss, but rather focussing on the stress state parameter water potential. Developing a 3-dimensional space of void ratio, moisture ratio and water potential will be a novel approach to extent the characterisation of the geomechanical properties of substrates by incorporating individual substrate specific pore size distributions and their behaviour towards internal (tensile/shrinkage) stresses and external stresses.

The PhD project will apply this information to improve numerical modelling and simulation of subsidence behaviour of various geological substrates and subsequent swelling potential by combining geomechanical data with hydrological information from the site and region.

The outcome of this work will create an advancement and novelty in the prediction of shrinkage/subsidence of substrates from the combination and linkages of hydrological and geomechanical properties. It will support the decision making process on the strategy and management of re-filling of the mine pits and inform about the risks of the occurrence of partial rebound, the occurrence of lateral stress and spatially non-uniform upheaval of land, which may cause deformation and cracking in the vicinity of mines and affect built-up environments.