Environmental Geomechanics for Cracking in Energy Resources Engineering

by

Dr.Manman HU

Assistant Professor, Department of Civil Engineering, HKU

Abstract

As the demand for energy worldwide keeps increasing, a potential engineering induced damage to the environment causes wide public concerns. New geo-energy technologies (e.g. unconventional shale gas, enhanced geothermal systems) need to incorporate intrinsic mechanisms to prevent negative impact to the environment, strategically inserted into the process from the design to the implementation phase, and hence warrant sustainable usage of energy resources. This type of approach in geomechanics is distinct from the classical one for the fact that it emphasizes the coupling of hydro-mechanical behavior of the geomaterial with the natural and engineered environment – including the temperature, chemical concentrations, mineral dissolution/precipitation, and other physical/chemical variables. 

This seminar focuses on a unique approach of tackling the fundamental multi-scale multi-physics problems of environmentally assisted crack propagation, with a long-term goal to control the effectiveness of treatment techniques and the extent of chemical footprint. The presentation consists of two parts. First, Mode I (opening mode) subcritical cracking is studied with an emphasis on the effect of the chemical environment. In particular, two constitutive frameworks, namely reactive-chemo-plasticity and reactive-chemo-elasticity, that allow the coupling of chemical mass removal (occurring on the solid-fluid interface at the micro-scale) into the plastic and elastic domain of rock behavior via different mechanisms, are developed and assessed. Subsequently, studies on Mode II (sliding/shear mode) cracking are presented via multi-physics modeling of shear instability and bifurcation through a damage mechanics implementation. Localized shear deformation around a borehole due to internal pressurizing (e.g. by fluid injection) is investigated with the role of temperature emphasized.

Biography

Dr. Manman Hu is currently an Assistant Professor at the Department of Civil Engineering, the University of Hong Kong. Her main research interests are in Unconventional Geomechanics, Multiscale Multiphysics Processes, and Environmental and Energy Sustainability. Before joining HKU, she worked as a Postdoctoral Research Fellow at UNSW Sydney on the Vice Chancellor’s Strategic Fund for Unconventional Resources. Dr. Hu holds a BEng in Civil Engineering from Zhejiang University, and a MSc and PhD in Civil and Environmental Engineering from Duke University.

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