The nature and engineering properties of some red soils from North-East Brazil

Researchers over the years have demonstrated the need for the determination of the nature and fundamental properties of soils as an approach to the understanding of engineering behaviour. This has teen shown to be particularly true in the case of tropical soils. This thesis approaches the analyses of engineering behaviour from a standpoint of the study of the intrinsic properties. The mineralogy, chemistry, structure and strength behaviour of three concretionary red soils from Paraiba State in North-East Brazil, have been determined. The mineralogy- of the red soils were determined using X-ray analysis, differential thermal analysis and thermogravimetric techniques. The microstructure of the red soils has been examined with the optical and scanning electron microscopes. The strength behaviour of compacted specimens was examined in the oedometer, direct shear and triaxial machines. A phenomenon of breakdown of soil particles under stress is isolated. The influence of the phenomenon on the strength behaviour is demonstrated. The soil elements and properties responsible for the phenomenon are discussed