TITLE:
On the Origin of the Cavities Present in the Sandstone Formations of the Hydroelectric Development Site of Kakobola and Its Surroundings (Kwilu Province/DRC)
AUTHORS:
Ivon Ndala Tshiwisa, Thomas Kanika Mayena, Dominique Wetshondo Osomba, Albert Mbata Muliwavyo, Brich Kalanga Kabuya, Jonathan Musitu Muliwavyo, Clement N’zau Umba-Di-Mbudi
KEYWORDS:
Development, Cavity, Drilling, Sandstone, Hydroelectric, Kakobola
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.11 No.4,
April
30,
2023
ABSTRACT: Problems due to underground cavities at the level of soft and polymorphic
sandstones, collapses and infiltration of acid waters through the fracture
networks have been observed around the Kakobola hydroelectric development,
constituting potential risks for the stability of the dam. The objective of
this article aims to highlight the major cause that can explain the generating
processes of these cavities. Indeed, to do this, the exploration of the subsoil
was made possible thanks to the eleven (11) boreholes drilled on the site, the
determination of cavities by the method of colored tracers and the petrographic
characterization using a microscope. The latter, by means of thin sections,
reveals the presence of quartz arenites. The mineralogical characterization of
rock materials was carried out using X-ray fluorescence and X-ray diffraction
methods. X-ray fluorescence revealed the presence of nickel, zinc and iron.
Diffraction shows us an abundance of silica, mainly quartz and its metastable
phases, in particular tridymite and cristobalite. It also made it possible to
question the presence of carbonated minerals. The drillings enabled us to
elaborate the logs and to bring out a geological model of the sector of study.
These models were produced on the basis of drilling and observations on excavation. These data also reveal the presence
of underground cavities which were also confirmed by the colored tracer method.
These cavities would be of natural origin due to the presence of
carbonate minerals observed in the rocks and which are attacked by acidic
waters attested by the pH 5 measurements of the waters of the Lufuku River. The infiltration of
water in rocky materials of low density and through the various networks of
fractures and cavities leads to instability of the rock and could damage the
hydroelectric development.