Cyclic strength of sand mixed with biochar: Some preliminary results

Biochar is a recycled material obtained through the thermal degradation of any organic biomass in the manufacture of bio-fuel inside a reactor in a process known as pyrolysis. It is an organic material that can endure in soil for thousands of years. Given its aromatic nature, biochar is highly recalcitrant, and has been considered to have great potential to sequester carbon and reduce greenhouse gas emissions. This material has been commonly used in environmental and agricultural applications, as it can store plant minerals in its pore spaces and provide a large water-holding capacity. However, little research has been done on the geomechanical properties of the resulting mixture of biochar and soil. Some studies have shown that biochar can increase the shear strength of clays and desaturate soil particles, and it may be possible that it can also increase the resistance to liquefaction in loose sand. Therefore, it would be very interesting to assess whether this material is able to present a more environmentally friendly alternative for improving the properties of soil. In this study, samples of pure sand are dry-mixed with 0%, 3%, and 5% biochar by weight and tested under cyclic undrained shearing using a simple shear test apparatus. The preliminary results indicate that biochar can increase the cyclic resistance of sand.