MICP联合纤维加筋改性钙质砂的动力特性研究

为了提高我国南海钙质砂地基的抗液化性能，提出利用微生物诱导碳酸钙沉积（MICP）技术联合纤维加筋技术对钙质砂进行改性处理。通过开展动三轴试验，对比分析了改性前后钙质砂试样的动应变、动孔压、应力?应变滞回曲线以及动弹性模量的发展规律和演化特征，并结合扫描电镜（SEM）试验探究了MICP和纤维加筋技术对钙质砂的联合改性机制。研究结果表明：（1）MICP技术可以明显改善钙质砂试样的抗变形与抗液化性能，相比于未胶结处理试样，仅MICP处理试样的动应变和动孔压分别降低了95.74% 和 92.46%；（2）纤维的掺入进一步提升了MICP的改性效果，相比于仅MICP处理试样，MICP和纤维加筋联合处理试样的动应变和动孔压分别降低了 74.32%和 74.18%；（3）MICP 和纤维加筋技术通过减轻试样在循环荷载作用下的循环活动强度和能量耗散、提高试样的动弹性模量和减小动弹性模量的衰减速率，从而实现试样抗变形与抗液化性能的显著提高；（4）SEM 试验分析结果表明，MICP 与纤维对钙质砂动力特性的改善具有协同作用。纤维的掺入为细菌提供了更多的附着场所，促进了碳酸钙晶体的生成量，该部分碳酸钙不仅增加了颗粒间的胶结强度，同时也将纤维固定在砂颗粒上增强了纤维网的约束作用。

Dynamic behaviors of MICP and fiber-treated calcareous sand under dynamic triaxial testing

To improve the liquefaction resistance of calcareous sand foundations, microbially induced calcium carbonate precipitation (MICP) technology combined with fiber reinforcement technology was proposed to treat the calcareous sand in the South China Sea. Based on dynamic triaxial tests, the dynamic behaviors of MICP and fiber-treated calcareous sand were studied. The dynamic strain, dynamic pore pressure, cyclic stress-strain response and dynamic elastic modulus were analyzed. Then, the strengthening mechanism of MICP and fiber on the mechanical properties of the treated calcareous sand was explored from the microscopic point of view, based on the scanning electron microscope (SEM) test results. The results show that: (i) MICP could improve the deformation resistance and liquefaction resistance of calcareous sands. Compared with the untreated calcareous sand samples, the dynamic strain and dynamic pore pressure of calcareous sand treated by MICP decreased by 95.74% and 92.46%, respectively. (ii) The addition of fibers further improved the reinforcement effect of MICP. Compared to the MICP-treated samples, the dynamic strain and dynamic pore pressure of MICP and fiber-treated samples decreased by 74.32% and 74.18%, respectively. (iii) MICP and fiber reinforcement technologies improved the deformation resistance and liquefaction resistance of calcareous sand subjected to cyclic loading by reducing the cyclic activity strength and energy dissipation, increasing the dynamic elastic modulus and reducing the decay rate of the dynamic elastic modulus. (iv) The results of the SEM test showed that MICP and fiber reinforcement had a synergistic effect on the improvement of the mechanical properties of calcareous sands. The incorporation of fibers provided more spots for bacterial adhesion and promoted the formation of calcium carbonate crystals, which not only increased the bonding strength between sand particles, but also enhanced the restraint of fiber nets by fixing fibers and sand particles together.