Evaluating Rock Construction Materials Using Petrography, Engineering Properties and Geophysical Investigation Around Hawassa, Sidama, Ethiopia

Abstract

 The petrographic description, engineering physical properties, and resistivity characteristics of rock construction materials determining the quality, durability and economic efficiency of infrastructures. The study area is situated at the marginal settings in the central and southern part of main Ethiopian rift, comprises diverse volcanic and pyroclastic rocks that are widely used in the varies construction materials but poorly characterized. The civil engineering infrastructures in Hawassa city and the Sidama regional state are deteriorating due to the inappropriate use of rock materials. Comprehensive studies on these construction materials have not yet been carried. The objective of the study was to evaluate quality of rock construction materials using petrography analysis, engineering physical property assessments and geophysical investigation. To attain this objective, 24 petrographic descriptions, 10 rocks engineering properties and 5 resistivity survey data were analyzed. The rock construction materials identified in the study area, including andesite, scoria, rhyolitic ignimbrite, ignimbrite, welded tuff, and pumice. From these, the andesite rock is composed of pyroxene (60%), plagioclase (35%), biotite (10%), and muscovite (10%) minerals, whereas the rhyolitic ignimbrite shows a flow banding texture, which contains feldspar (40%), plagioclase (25%), biotite (15%), quartz (10%), and volcanic glass (10%) minerals. The dominant structures of the study include joints, cracks, and faults are oriented NE to SW which controlled by main Ethiopian Rift system. The vertical electrical sounding results indicate that the Alamora andesite outcrops, the Boricha quarry site and Gemeto Gale area contain a potential rock layer that suitable for various infrastructures. The lowest and highest compressive strengths are observed in the Galoko Haro quarry site and Alamora andisite rock, which have values ranging from 8 N/mm² to 300.5 N/mm², respectively. The study identified potential rock for sustainable use in various infrastructure developments, providing a foundational dataset for researchers and the Sidama Regional State Mining and Energy Bureau.