VAC-2021-31 - PhD Position in Structural Mechanics Group: “A Discrete Element Method for modelling sandstones under regular and extreme loads”

Title of the PhD project: A Discrete Element Method for modelling sandstones under regular and extreme loads

The term ‘sandstones’ covers a wide range of rocks, from very soft to moderately strong, slightly permeable to very permeable and unconsolidated to overconsolidated. They have a wide variety of uses and also present a relatively high permeability, which makes them an attractive scenario for extracting water, oil and gas. They are also useful for injecting these same substances, for instance in the case of atmospheric CO2 sequestration.

The detailed behaviour of sandstones at certain depths is largely unknown due to the difficulty in reproducing the same conditions in experimental laboratories. Thus, a good, reliable model of the sandstone behaviour can bring valuable insight on the processes occurring at high depths, or those which might occur, but also valuable information about the stiffness and strength of the same material when it is located at surface level, along with more detailed processes like grain detachment or crack propagation. This knowledge can increase safety levels not only for neighbouring communities, but to the environment as well, preventing filtrations or induced seismicity.

Some of the best attempts to reproduce the behaviour of sandstones as based on the Parallel Bond Method (PBM, [1]), consisting on a dual force between Discrete Element Method (DEM) particles: one modelling the unbonded phase and the other modelling the bonded, also called cementitious, phase. However, the current models fail to cover the full range of properties of the sandstones. They are not, for example, capable of dealing with pre-stressed sandstones (extracted from high depth), or rarely deal with the cataclasis phenomenon (breakage of sand grains).

The PhD project will consist in developing a general numerical model for sandstones, including the major driving characteristics of its microscopic behaviour when the size of each particle of the model is that of an actual sand grain. The work must try to cover the widest possible range of rock types and load types. The Kratos Multiphysics DEM [2, 3] will be used as a starting point, as it already features a PBM implementation.

The functions assigned to the candidate will be:

• Complete a PhD on Structural Analysis at Universitat Politècnica de Catalunya – Barcelona Tech. The candidate is expected to complete the PhD thesis in a maximum of three years.
• Collaborate with various research groups within CIMNE and worldwide.
• To publish a minimum of two papers in JCR journals during the PhD period, author and co-author articles in high-impact international journals
• Carry out quality research, training and management.
• Participate on the dissemination and outreach activities associated with the project
• Participate in international conferences presenting her/his work