An experimental investigation of the influence of weathering on saprolitic soils from Hong Kong

Abstract

A good understanding of soil mechanics has been achieved in the last decades for sedimentary soils. Frameworks have been put forward to explain their behaviour both in intact and reconstituted states. However, the extent to which these frameworks are applicable to intact saprolitic soils is less well understood. Since saprolitic soils are present extensively in many developing countries, a systematic research on their behaviour should have worldwide influence. This research focused on the experimental investigation of the mechanical properties of intact samples of one coarse grained and also a range of fine grained saprolites. A weathered profile in the coarse grained saprolite was used to ascertain how the evolution of the weathering process modifies the soil properties. The amount to which the properties of the parent rock contribute to the behaviour of a weathered soil was instead ascertained using different fine grained saprolites. The behaviour at small strains was investigated with a combination of bender elements and high resolution local strain gauges, whereas the behaviour at large strains was investigated with oedometers and triaxial tests at standard and high pressures. This work showed that the critical state framework can be applied to intact saprolitic soils accounting for the effects of structure, although fine grained saprolites might not have a clear unique Normal Compression and/or Critical State Lines. Very different properties and mechanical behaviours can be observed within the same weathering grade for intact specimens, which calls for a more appropriate classification to be applied. However, it appears that the reconstituted specimens behave with more similarity, having only slight differences in compressibility and the location of the Normal Compression and/or Critical State Lines. After normalisation is applied, the effects of structure generally reduce with depth in the volumetric plane, but the opposite is observed in terms of strength.

Date of Award	3 Oct 2014
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Matthew Richard COOP (Supervisor)