MICP-FR协同作用改善钙质砂的力学性能及抗侵蚀试验研究

Experimental study on surface erosion resistances and mechanical behavior of MICP-FR-treated calcareous sand

南海岛礁是中国"一带一路"建设的重要支撑。作为岛礁工程的主要建筑材料和地基,钙质砂具有高孔隙、易破碎和强度低等不良特性,难以直接满足工程建设要求。为了改善钙质砂的力学特性,并减少极端暴雨冲刷导致的侵蚀问题,提出微生物诱导碳酸钙沉积(MICP)协同纤维加筋(FR)改性技术,采用喷淋工艺,对浅表层钙质砂进行改性处理,并考虑胶结液浓度(0.5,1.0,1.5,2.0mol/L)和纤维掺量(0.1%,0.2%,0.3%,0.4%)对处理效果的影响。通过开展超微型贯入及模拟暴雨冲刷试验,结合冲刷后滤出溶液的电导率变化,对比分析了不同处理方式下钙质砂的胶结固化程度和抗侵蚀能力。研究结果表明:(1)MICP技术可以有效胶结钙质砂,改善其力学性质,胶结液浓度越高,试样碳酸钙含量和贯入阻力越高,2.0mol/L固化效果最佳;(2)纤维的加入能显著提升MICP的固化效果,纤维掺量对微生物固化试样的力学特性有重要影响,峰值贯入阻力随纤维掺量先增加后减小,最优纤维掺量为0.2%;(3)经过MICP固化处理后,试样在模拟暴雨条件下表现出较好的抗雨蚀能力,侵蚀量小于未处理试样的1/7,加入纤维后胶结试样的抗侵蚀能力更佳。MICP-FR协同作用可以高效改善钙质砂的工程特性,能在岛礁建设、海岸开发过程中发挥积极作用。

The islands and reefs in South China Sea are an important support for China’s"One Belt and One Road Initiative".As the main building material and foundation of construction on the islands and reefs,the calcareous sand has the bad characteristics of high porosity,easy breakage and low strength,so it is difficult to directly meet the requirements of engineering construction.In order to improve the mechanical behaviors of the calcareous sand and reduce the erosion problems caused by extreme rainstorms,an eco-friendly,cost-effective microbial-induced calcium carbonate precipitation(MICP)synergistic fiber reinforcement(FR)modification technology is proposed.The superficial layer of the calcareous sand is modified by spraying process,and the influences of the cementing liquid concentrations(0.5,1.0,1.5,2.0 mol/L)and the fiber contents(0.1,0.2,0.3,0.4%)on the treatment effect are considered.The cementation degree and surface erosion resistance of the calcareous sand under different treatment methods are analyzed by carrying out mini-penetration tests and simulated rainstorm scouring tests combined with electrical conductivity.The results show that:(1)The MICP technology can effectively cement the calcareous sand and improve its mechanical behaviors.The higher the cementing liquid concentration,the higher the calcium carbonate content and the penetration resistance of the samples,and the curing effect with the concentration of 2.0 mol/L is the best;(2)The addition of fiber can significantly improve the cementing effect of MICP,and the fiber content has an important influence on the mechanical behaviors of the microbial solidified samples.The peak penetration resistancefirst increases and then decreases with the fiber content,and the optimal fiber content is 0.2%;(3)The MICP-treated samples show better erosion resistance under the simulated rainstorm condition,the erosion amount is less than 1/7 of the untreated samples,and the effect is better after adding fiber.MICP-FR synergy can effectively improve the engineering properties of the calcareous sand and play an active role in the island construction and coastal development.