Basic Physical Properties and Mechanical Behavior of Compacted Weathered Granite Soils

Abstract

Weathered granite soils are abundant in China and used extensively as backfill materials. However, there is less systematic research on weathered granite compared with sedimentary types of soils, such as sand and clay. In this study, a series of laboratory tests was performed, including X-ray diffraction, sieving, expansion potential, compaction, California bearing ratio (CBR), and large-scale triaxial tests, to study the basic physical properties and mechanical behaviors of weathered granite soil. Results of the laboratory tests indicate that a clay content of 8% could be a good indicator to determine the compaction characteristics of weathered granitic soil with differing clay content. Thus, weathered granite soil with a clay content of approximately 8% would be advantageous to reach and maintain the compaction rate of subgrade and the stability of roads. However, the weathered granite soil with a clay content of approximately 4% had the largest mean value in the CBR tests, which was 95%. The critical confining pressure (100–200 kPa) is an indicator to determine the hardening characteristics of compacted weathered granitic soils under different pressures. The experimental results show that the samples exhibited different dilatancy characteristics under different confining pressures because the internal particles of the samples might have been compacted, dislocated, overturned, or broken and that the increase in peak deviatory stress resulting from an increase in mean stress was nonlinear because of particle breakage.