沙漠风沙土的微生物固化机理及抗侵蚀性能研究

As the new era of Microbial Induced Carbonate Precipitation (MICP) is emerging and promising so many new applications in geotechnical engineering. The MICP-mediated aeolian sandy soil is generated based on Ureolysis, and it has strong vitality increasingly in desert engineering to control the erosion. Firstly, the experimental preparation method and technology is suggested, and it is an important challenge to prepare the uniform sample. The basic bio-geotechnical and mechanical properties, weatherability and freezing-thawing resistance performance are measured, and the biocompatibility is evaluated between the microorganism and the soil. Then, the microstructure characteristic of sample surface and internal are tested, and pore distribution within the sample is probed. It is an innovative method to evaluate and feedback the uniformity of artificial materials. The reinforce mechanism of MICP-mediated aeolian sandy soil is indicated. Finally, take bio-crust as engineering prospect, the wind erosion resistance ability is detected, and its performance is evaluated in long-term harsh desert environments. All these information obtained from the proposal will help us to understand bio-geotechnical properties of MICP-mediated aeolian sandy soil, to draw a prospective advanced research for application prospect of bio-crust in desert engineering, and to provide the theoretical and experimental basis for bio-geotechnical reinforcement mechanisms in bio-technology combined with desert engineering practice.

运用基于尿素水解的微生物诱导碳酸钙(MICP)矿化技术，对沙漠风沙土进行固化改性，生成微生物诱导矿化风沙土的新型土工材料。研究该新型土工材料的实验室制备方法和工艺，测试其生物岩土力学性能、耐候性能及抗冻融侵蚀性能，对微生物菌种与风沙土基质间的相融亲和性进行试验验证。测试该新型土工材料的微观结构特性，及诱导生成的胶结物在岩土基质孔隙间的分布情况，对人工材料的制备以及均匀可靠性进行过程监控与信息反馈，结合宏微观试验结果揭示微生物诱导矿化风沙土的固化机理。进而，以沙漠生物覆膜作为工程运用前景，研究该人工沙漠生物覆膜的模型试验方法，对沙漠特有的恶劣环境下，人工沙漠生物覆膜的抗风沙侵蚀能力进行科学评价和前瞻性预研。项目预期研究成果将为绿色生物科技与沙漠工程相结合背景下的新型土体固化改性技术提供理论和试验依据。

应用微生物诱导碳酸钙沉积(MICP)技术对沙漠风沙土进行矿化加固。针对沙漠风沙土的颗粒细小、均匀，粒间无粘聚力，易风蚀等特殊性质，研发了微生物诱导矿化沙漠风沙土的室内试验装置及制备方法；研究微生物诱导矿化沙漠风沙土的成因机理及矿化前后孔隙的变化特征；研究微生物诱导矿化沙漠风沙土的改进技术，提出通过添加胞外多糖来改善颗粒间以及颗粒与碳酸钙晶体间的粘聚力，改善传统的微生物矿化岩土材料脆性特征。考虑沙漠环境的特点，研究微生物诱导矿化沙漠风沙土的抗紫外、冻融、高低温、风蚀、干湿循环等耐候性能，以及耐复合侵蚀及酸/碱/盐腐蚀特性，评价其在恶劣的沙漠环境中碳酸钙联结是否稳定可靠。进一步，选择内蒙古自治区乌兰布和沙漠腹地为试验场地，自沙漠风沙土中提取具有矿化效果的自源葡萄球菌，将微生物诱导矿化技术应用于沙漠原位覆膜的形成，使得流动沙丘经结皮固定而成为半固定、固定沙丘，从根本上阻断沙尘暴的源头。现场测试结果显示，沙漠覆膜的平均厚度为2.0～2.5 cm，经自源葡萄球菌诱导生成的矿化覆膜较传统的巴氏芽孢杆菌诱导生成的矿化覆膜具有更好的强度表现和沙漠环境中的耐久性。微生物覆膜表现出与岩土基质亲和性、良好的透气透水性、环境友好、绿色环保等特点，让它成为沙地生态治理中“会呼吸的天然屏障”，这是绿色生物技术与沙漠治理相结合背景下特殊土改良技术的新突破。项目研发过程中，考虑到微生物菌种的培育及现场实施的困难，研发了矿化菌种的破胞技术，首次尝试对矿化菌种进行破胞提取胞內外脲酶，并对脲酶沉积碳酸钙的固化效果进行试验验证。