TITLE:
An Experimental Study on Measurement Methods of Bulk Density and Porosity of Rock Samples
AUTHORS:
Weiren Lin, Osamu Tadai, Manabu Takahashi, Daisaku Sato, Takehiro Hirose, Wataru Tanikawa, Yohei Hamada, Kentaro Hatakeda
KEYWORDS:
Rock, Density, Porosity, Caliper Method, Buoyancy Method, Helium-Displacement Pycnometer, Mucury Intrusion Posimetry
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.3 No.5,
July
17,
2015
ABSTRACT: Density and porosity are fundamental and
important physical properties of rocks in various geological problems, and
affect the other physical properties. Therefore, measurements of density and
porosity of rock samples are important investigation items in both geo-science
and geo-engineering areas. Several measurement techniques of the density and
porosity are available and being applied currently. To ensure the data quality
and to conduct its quality assessment, comparison of measurement results by
different measurement techniques is necessary since the techniques are based on
different principles and test procedures. In this study, we collected eight
types of rock samples including a gabbro, a granite, four sandstones, a welded
tuff and a mudstone as study materials, and also prepared several metal
specimens for the experimental comparison. The porosities of the eight rocks
covered a very wide range from 0.3% to 50% approximately. We employed three
methods (caliper, buoyancy and helium-displacement pycnometer) to measure
volumes of regularly-shaped specimens and to determine their bulk densities and
porosities. As a result, the three techniques yielded almost same bulk
densities and porosities for all the specimens. In addition, we also applied
mercury intrusion porosimetry to measure density and porosity as well as to
determine pore size distribution of the rock samples. Porosity values obtained
by the porosimetry method were underestimated in the case of high-porosity
(soft) rock samples and overestimated for the very low-porosity rock samples.
Ability to determine pore size distribution, however, is a very important
advantage of the porosimetry method.