Abstract

The aim of this study is to characterize the alluvial gravel of the Niari river in Congo, to improve its geotechnical properties by stabilizing it with a clayey soil and to find out its utilization in the road construction according to the approved standards in most African countries. The results show that the grain size distribution of the alluvial gravel fits in the standard envelope of the base layer and its resistance to friction of 23% is within the allowed limits. However, its fines content and plasticity index are respectively 4 and 0%, out of the allowed range. Adding the clayey soil increases the CBR index from 0 for the alluvial gravel to 142% for a mixture of 15% of the clayey soil, while the sand equivalent decreases from 80 to 42%. The mixtures of 5, 10 and 30%, respectively of the clayey soil content could be used as the subbase layer in the road construction; that of 15% as the base layer for T3 and T4 traffics and those of 20 and 25% as the base layer for T1 and T2 traffics. Besides, it is found that the CBR index of the mixture of the CBR index is strongly correlated to its density and the relationship between them is parabolic.

Keywords:

Alluvial gravel, clayey soil, geotechnical properties, litho-stabilization, road,

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Competing interests

The authors have no competing interests.

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