LAUSR

In recent years, biochar has been widely used in environmental and geotechnical engineering applications, but minimal studies have been done on its influence on soil engineering properties. In this study, the effect of biochar on the compression and swelling characteristics of two clayey soils, namely PKE and XS, was studied by conducting standard consolidation tests and no-load swelling tests. The compression curves and swelling parameters of modified clays with different biochar content (0, 0.5, 1, 2%, w/w) and biochar particle sizes (< 0.15, 1–2 mm) were obtained. The microstructure of the biochar-clay mixture was analyzed by scanning electron microscopy (SEM) test. The results showed that: (1) the compressibility of clayey soils can be effectively reduced by adding biochar, and this effect is more significant with the increase biochar percentage; (2) the effect of reducing soil compressibility by fine biochar was better than coarse biochar; (3) under the same pressure, the settlement rate of soil increased with the increase of biochar content; (4) the incorporation of biochar had no obvious influence on the no-load swelling behaviour of PKE while it has significantly increased the swelling of XS (low expansive soil). Additionally, the fine-grained biochar has a significant effect than the coarse-grained biochar on clayey soils.