Avalanches and failures in bio-stimulated soils

Bio-stimulation is a popular method to improve the engineering properties of soils because it treats the soils by using native bacteria which is environmentally friendly. However, the failure mechanism of bio-stimulated soils has not been studied. In this work, we apply avalanche dynamics which has been used in the investigation of bio-augmented sands to analyze the avalanche characteristics and failure mechanisms of bio-stimulated soils. We find the average relative magnitude, waiting time distribution and aftershock distribution are independent of the degree of cementation when the calcium carbonate precipitation content ranges from 14% to 27%. Additionally, the exponents in the mean-field thory indicate the failure of bio-stimulated soils is not brittle. Furthermore, we find the failure mechanism of bio-stimulated soils is a mixture of fracture and intergranular movement. During the failure process of bio-stimulated soils, the fracture behavior becomes more obvious with an increase in degree of cementation. At the pre-peak stage, the proportion of intergranular movement gradually increases in the mixture of fracture and intergranular movement with the loading process. The main failure mechanism at the whole stage and post-peak stage is intergranular movement. The findings may contribute to the further investigation of the mechanical behavior exhibited by bio-stimulated soils.