基于冰核活性细菌的高温冻土强度增强特性及模型研究

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

    • 摘要: 冻土中赋存的冰核活性细菌具有高温成冰特性。然而,利用本土生物资源催化高温冻土孔隙水相变为冰以改善冻土强度的方法鲜有记载,也未有相关模型从细观角度描述外力作用下冰核活性细菌对高温冻土强度影响特征。因此,聚焦冰核活性细菌丁香假单胞菌高温冻土,通过核磁共振及直剪试验获取不同丁香假单胞菌浓度、冻土温度及法向压力下冻土未冻水含量、剪切变形行为及剪切强度变化规律,建立丁香假单胞菌高温冻土本构模型。结果表明:丁香假单胞菌使高温冻土未冻水含量降低17.09% ~ 41.36%。冻土强度增长归功于促生的冰晶在不同温度下的贡献:在−1℃时,粘聚力增加58.44% ~ 112.99%,剪切强度增长9.09% ~ 64%;在−0.5℃和−0.1℃时,内摩擦角增长18.42% ~ 47.85%,剪切强度增长0.99% ~ 33.96%。高法向压力削弱丁香假单胞菌对高温冻土强度的增强作用。所得本构模型为冰核活性细菌高温冻土地基承载力数值模拟及安全评价提供理论支撑。

       

      Abstract: 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.

       

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