Degree of weathering in the identification of laterite materials for engineering purposes — a review

Abstract

Laterite materials include a large succession of reddish, tropically weathered, decomposition products starting with fresh rock and ending with sesquioxide-rich pedogenic rock (cuirasse). Identification of the various grades of such materials for engineering purposes is a problem which repeatedly faces the engineer engaged in the design and construction of structures on or with laterite materials. The author has attempted to assemble available information useful for the identification and evaluation of all grades of laterite materials for engineering purposes. In the first part he summarises information on the significant genetic characteristics which appear to underlie the deviation of engineering behaviour of laterite materials from the expected properties based upon conventional soil mechanics as developed for temperate-zone soils. The second part summarises available information on the identification of significant geotechnical properties of various grades and genetic groups of laterite materials for engineering purposes. The engineering behaviour of laterite materials forms the substance of the third part of the paper. A literature study has revealed that the geotechnical characteristics and engineering behaviour of laterite materials depend mainly on the genesis and degree of weathering (i.e., decomposition, laterisation, dessication and/or hardening). Other significant genetic characteristics include morphological characteristics as well as the type and content of secondary minerals. Progress in the field of identification and evaluation of laterite materials for construction appears to depend on the simultaneous consideration of all the major factors which affect the behaviour of rocks and their derived soils (i.e., rock type, weathering condition, degree of weathering, type of derived materials as well as their chemical and mineralogical composition). Such an approach is desirable to increase the accuracy of predictions and assessments of the engineering behaviour of most laterite materials.