不同含水状态下微生物珊瑚砂桩单桩复合地基模型试验研究

微生物珊瑚砂桩复合地基是利用MICP技术固化珊瑚砂成桩与珊瑚砂组成复合地基，具有就地取材、对原状砂土扰动小及对岛礁生态环境影响小等优势，在岛礁工程建设中具有良好的应用前景。通过不同工况下的微生物珊瑚砂桩单桩复合地基模型试验，研究地基相对密实度（50%、65%、72%）、面积置换率（8%、14%、20%）、含水状态（干燥和饱和）和水位升降对复合地基承载特性的影响规律。结果表明：干燥状态下复合地基的承载力及桩侧摩阻力随地基相对密实度和面积置换率增大而增大；复合地基的桩身轴力和桩土应力比随地基相对密实度增大而减小，随面积置换率增大而增大；提高地基相对密实度和面积置换率可有效提高复合地基承载力。饱和状态下复合地基的承载力为干燥状态的49%~66%；饱和状态相对于干燥状态桩身最大轴力和桩侧摩阻力减小，桩土应力比增大。两次水位升降对微生物珊瑚砂桩单桩复合地基的承载特性影响较小。

Experimental study on single pile composite foundation model of biocemented coral sand pile under different water content states

The microbial coral sand pile composite foundation is composed of coral sand and coral sand piles solidified using MICP, which has the advantages of the ability to obtain local materials, less disturbance to the ground and marginal effects to the ecological environment of islands and reefs, and has good application prospects for construction of islands and reefs. Through the model test of single pile composite foundation of biocemented coral sand pile under different working conditions, the influence of relative density (50%, 65%, 72%), area replacement rate (8%, 14%, 20%), water content (dry and saturated) and water level fluctuation on the bearing characteristics was revealed. The test shows that in the dry state, with increase of the relative density and the area replacement rate, the bearing capacity and the pile side friction of the single pile composite foundation of biocemented coral sand pile increase. The axial force of the microbial coral sand pile and the stress ratio of pile and soil decrease with increase of the relative density, and increase with the area replacement rate. The bearing capacity of composite foundation can be effectively improved by increasing the relative density and area replacement rate. The ultimate bearing capacity of the single pile composite foundation of biocemented coral sand pile in the saturated state is 49%-66% of the bearing capacity in the dry state. Under the same upper load and area replacement rate, compared with the dry state, the pile side friction resistance and the maximum pile axial force of the composite foundation in the saturated state decrease, the stress ratio of pile and soil increases. The twice water level rises and falls have marginal effect on the bearing characteristics of single pile composite foundation.