A study of the microstructure to assess the reliability of laboratory compacted soils as reference material for earth constructions

摘要

Specifications for earth constructions are based on criteria derived from the hypothesis that the compacted soil in the field will behave as the reference material compacted in the laboratory through standard procedures. It is well known that different compaction procedures may create different microstructures for the same soil. As the microstructure plays an important role in the overall hydro-mechanical behaviour of compacted soils, it should be carefully considered when a reference material is adopted to characterise a given soil as construction material. An experimental investigation, aimed at devising and suggesting appropriate techniques to get a reliable reference material for earth constructions, was programmed. The investigation included a study of the microstructure of field-and laboratory-compacted clayey soil, performed by means of scanning electron microscope observations and mercury intrusion porosimetry. The main results of the investigation are summarised in this paper. The differences already observed at the microstructure level pose the question whether the soil compacted in the laboratory adopting the standard procedures should be effectively considered as a correct reference material.