Characterization with geotechnical testings of the clay sediments of Gbédji-Kotovi in Benin

Abstract

Background: The clay of Gbédji-Kotovi is a combination of smectites, and of beidélite (Etienne SAGBO, 2015; IHETA and al, 1983), which presents sometimes, heterogeneous (mixtures) and anisotropic (multilayers) states. In Africa, generally, clays are used in the homogen soil constructed core or body ofdykes, or in the construction ofzoned backfill water resistant core or body of dikes or dams and for the masqued backfilled dykes. Thus, it is importantto prove with the geotechnical testings, if the clay of Gbédji-Kotovi can be used for dykes or dams. Objective: This paper identifies, classifies and determines the mechanical behavior of the clay sediments obtained from two wells of Gbédji-Kotovi clays deposit. Results : The results of the testings are the follows: the clay sediments of well number 1 have a texture with 59 to 81% of fines, the water content is between 10% and 40%, the low friction angles is from 0.63 to 5.8 ° and high internal cohesions is from 13 kPa to 22 kPa. On the other hand, the sedi-ments of well 2 have avarious textures (sandy-clay-loam, clay-loam and clays), the average friction angles is from 14°C to 24.4°, weak or medium inter-nal cohesions is 9.59 kPaat 49 ° C, the high dry density is 1.75 t/m3, the low water content ,13%,the low CBR, 07 and the average swelling rate is 0.2369%. Conclusion: the use of those clays for the construction of dikes is approved by the obtained results. Some reconstitutions ofsamples of sand-clay, in the laboratory are also reproduced and the different real cases of natural masses (heterogeneous and anisotropic) observed in situ, were tested. Finally, the proportions of 21.3% of clay, 0.5% of loam, 68.2% of coarse sand and 10% of gravelimproved significantly the following parameters: the water content is 6.9%,the density is 2.06t/ m3 , the average CBR is 20 andthe low swelling rate is 0.0790%. The clay of Gbédji-Kotovi can be used for the construction of the dykes. It is however necessary to study their permeability in situ and in the laboratory and to propose an improvement of their mechanical parame-ters thanks to a coarser sand.