Study on the Ice Nucleation Active Bacteria-Based Strength Enhancement Characteristics and Model of High-Temperature Frozen Soil

Ice nucleation active bacteria lived in frozen soil exhibits high ice nucleating activity. However, improving the strength of high-temperature frozen soil by facilitating pore water ice phase transition using local sustainable bio-resources ice nucleation active bacteria is rarely mentioned. The model described the effect of ice nucleation active bacteria on the strength of high-temperature frozen soil from microscopic perspective also remains unknown. Thus, the variation law of unfrozen water content, the shearing-deformation behaviour and the shear strength of frozen soil under different Pseudomonas syringae concentrations (0 ~ 20 g/L), soil temperatures (−0.1℃ ~ −1℃) and normal stresses (100 kPa ~ 400 kPa) were obtained by carrying out nuclear magnetic resonance and direct shear tests. Based on the binary medium model theory, the constitutive model of high-temperature frozen soil considering the effect of P. syringae on the elastic modulus of bond element and the factors of frictional element was established by introducing the breakage parameters and the volume strain rate. Results show that P. syringae caused a decrease in unfrozen water content by 17.09% ~ 41.36%. The shear strength enhancement is due to the contribution of increased ice crystals at different soil temperatures. At temperature of −1℃, the cohesion increased by 58.44% ~ 112.99%, correspondingly, the shear strength increased by 9.09% ~ 64%. At temperature of −0.1℃ and −0.5℃, the shear strength increased by 0.99% ~ 33.96% due to the internal friction angle increased by 18.42% ~ 47.85%. High normal stress undermines the enhancement effect of P. syringae on the strength of high-temperature frozen soil. The constitutive model can describe the deformation properties of high-temperature frozen soil affected by P. syringae from microscopic perspective, and provide theoretical basis for numerical simulation of the load-bearing capacity and safety evaluation of high-temperature frozen soil with ice nucleation active bacteria.