Effect of biochar on the geotechnical properties of saturated sand

Biochar is a carbonaceous matter produced by heating any organic biomass in an oxygen-free environment through pyrolysis. Biochar has several properties that make it an environmentally friendly material. For instance, given its aromatic nature, biochar is highly recalcitrant, so it has great potential to sequester carbon and reduce greenhouse gas emissions. Additionally, due to its highly porous nature and a high specific surface area, biochar can be effectively used for the removal of contaminants from soil and groundwater. Since most of the research on biochar applications are about their use as a soil amendment, it is essential to assess its influence on soil properties from a geotechnical point of view. To date, little work has been done in this field. In this study, the effect of biochar addition at various amounts (3% and 5%) on the liquefaction resistance of loose saturated sand is investigated through simple shear tests. The results show that the addition of biochar increases the liquefaction resistance of sand by delaying the generation of excess pore water pressure and restraining shear strain development. In addition, the results for sand with 5% biochar are compared with those for sand with 5% fines content (silt), and the difference between them is considerable; implying that the mechanism by which biochar increases liquefaction resistance is different from just adding fines to the sand. The interaction between biochar and water is studied by rheological tests and ESEM analysis to provide an insight into the improvement mechanism. The results presented in this paper provide evidence that this material has the potential to be used for mitigation of soil liquefaction.