The textural and petrographic characteristics of the soils of the city of Amtiman and their behavior on swelling and shrinkage are presented here.The soils of the town of Amtiman (Chad) have a predominantly clay texture and the clays are mainly exposed on the surface. The results of this work include characterizing the type of clay present in the city. These are the heterogeneous layers of clayey soils consisting mainly of surface-bound illites but also of kaolinite intercalation at depth.These results suggest that the phenomenon of shrinkage of the clays (Illite and kaolinite) of the city of Amtiman is very low and that this city belongs to the sedimentary basin of Salamat.

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This work deals with the petrographic and geotechnical characterization of rocks from the N'goura massif with focus on their use in civil engineering. The study area is located in central southern Chad, about 205km to the north of N'Djamena. The N'goura massif is monzogranitic with two micas. The rocks outcrop as blocks, slabs and balls displaying fine, medium and coarse grained minerals. Monzogranite is composed of 34% quartz, 32% alkali feldspar, 26% plagioclase, 4% biotite, 2% muscovite and 1% chlorite on average. Geotechnical data show that the aggregates obtained from this rock have a Los Angeles coefficient ranging from 22.70 to 38.70% with an average of 30.70%, a Microdeval coefficient ranging from 4 to 13% with an average of 8.5% and a dynamic fragmentation coefficient ranging from 11.43 to 18.57% with an average of 15%. These results indicate that the studied materials are suitable to be used for construction and civil engineering works. The correlation between petrographic and geotechnical data reveals that the size (texture), grain structure and mineralogical composition (Qtz, Kfs and Bt+Ms+Chl+Ser) have an influence on the geotechnical behavior of these materials.