Title: Analysis of poroelasticity and chemically-assisted crack growth 
Resource Type: document --> technical publication --> report 
Country: EU Projects 
Year: 2003 
Availability: Saltrans Consortium, 2003,Analysis of poroelasticity and chemically-assisted crack growth http://www.weizmann.ac.il/ESER/Saltrans/Deliverables.html 
Author 1/Producer: Saltrans Consortium 
Author / Producer Type: EC Project 
Report / download web link (=direct link): http://www.weizmann.ac.il/ESER/Saltrans/Deliverables.html  
EUGRIS Keyword(s): Contaminated land-->Soil and groundwater processes-->Hydrogeology
Groundwater protection-->Groundwater processes-->Hydrogeology
Water resources and their management -->Water resources and their management Overview
 
Short description: This report comprises Deliverable 6 for the SALTRANS project (EVK1-CT-2000-0062). This deliverable is linked to Work Package 2, and relates to the activity “Quantification of dynamic (evolving) structural changes, due to deformation, poroelasticity and fracture growth processes”. 
Long description: Poroelasticity. When fluid is injected into a compliant fracture, the effective stress at the injection point is then the difference between the tectonic stress and the pore pressure. This stress perturbation is not just local, but also affects the long-range stress field, decaying inversely with distance squared. An increase in local pore pressure can also open up fractures, resulting in an exponential increase in permeability as the effective stress is decreased. Similarly a drop in pressure due to high pumping rates can close conducting fractures. This feedback can result in a non-linear pressure diffusion field with a perturbation on the Fickian solution for fluid pressure diffusion in a homogeneous medium solely due to the stress-sensitivity of the permeability. Huc & Main (2003) have developed a numerical finite element model for the coupled evolution of a poroelastic stress field for the problem of fluid injection. The results predict non-Fickian diffusion of the pore pressure field that may have to be taken into account in some of the field tests if (a) the rock has compliant fractures and/or (b) high pore fluid pumping rates are used. This work is now completed, and is currently being written up for publication. Chemically-assisted crack growth. Recent experimental results (Ojala et al., 2003) have comfirmed a strong correlation between acoustic emission event rate and the rate of dissolution of silica during the fracturing of porous Aeolian sandstones. The acoustic emission technique detects growing microcracks, and the increased dissolution of silica confirms that the microcracks are growing by enhanced chemical reactions, i.e. by the stress corrosion mechanism. This result has been reported before for purely tensile loading, but here the microcracks are growing in compression, simulating conditions in a sub-surface aquifer. The cumulative acoustic emission energy can be used as a damage parameter to reconstruct the stress history for dilute distributions of microcracks. The results predict the evolution of the early part of the stress-strain curve very well. The work is completed, and the paper submitted. 
Link to Project(s): SALTRANS Methods for assessing salt intrusion and transport in heterogeneous and fractured aquifers
 
Submitted By: Dr Stefan Gödeke WhoDoesWhat?      Last update: 22/10/2006