DBPapers
DOI: 10.5593/sgem2012/s02.v2005

COMPARATIVE ANALYSIS OF THE MOISTURE AND POROSITY INFLUENCE ON THE STATIC AND DYNAMIC ELASTICITY MODULUS

C. DANCIU, V. ARAD, R. MORARU, T. GOLDAN, C. DANIEL NISTOR
Wednesday 1 August 2012 by Libadmin2012

References: 12th International Multidisciplinary Scientific GeoConference, www.sgem.org, SGEM2012 Conference Proceedings/ ISSN 1314-2704, June 17-23, 2012, Vol. 2, 33 - 38 pp

ABSTRACT

Elastic characteristics of rocks can be influenced by various factors of different nature,
both external and internal. Among internal factors, moisture content and porosity
significantly influences static and dynamic elasticity modulus. Humidity has a decisive
influence on the elastic behavior of rocks, leading to an artificial increase of the elastic
characteristics values dynamically determined and having an adverse effect on the
elastic characteristics determined statically. An increase in porosity leads on the one
hand, to a decrease in the values of elastic characteristics determined dynamically and
statically, and on the other hand (with moisture intake) it can lead to an increase in
elastic characteristics determined dynamically. This paper presents the results of tests
performed on various types of igneous rocks, submitted to static and dynamic stresses.
Tests were performed in Geo-Mechanics Laboratory within the University of Petroşani.
The calculated values of static and dynamic elastic modules for different types of
igneous rocks were analyzed and compared in the laboratory, both for dried samples
with natural moisture and for saturated samples. Under the influence of moisture and
porosity, modules showed significant variations even within the same type of rock.
Moisture content has a large enough influence on the elastic characteristics determined
dynamically, meaning that dynamic modulus value increases for intact rocks,
proportionally with the water content increase. This behavior may be due to the fact that
the elastic wave propagation speed is higher in water than in air, and as the water
saturation of the sample the environment becomes more homogeneous. It was also
found that through rock drying, the phenomenon can be reversed only if the components
did not react with minerals in the water saturation process.

Keywords: porosity, moisture content, strain, modulus of elasticity.