MICP固化松散砒砂岩抗水蚀机理研究

Study on the Mechanism of Resistance to Water Erosion of Loose Pisha Sandstone Solidified by Microorganisms

[目的]探究MICP固化松散砒砂岩效果,为减少砒砂岩区水土流失提供解决方案与理论依据。[方法]从宏观尺度(贯入强度、降雨侵蚀等)探究菌液浓度和固化频次对MICP固化砒砂岩对力学性能及其抗水蚀性能的影响,并在微观尺度(X射线衍射、扫描电子显微镜、傅里叶红外光谱、热分析)解释了砒砂岩固化土的抗水蚀机理。[结果]相同固化次数下菌液浓度(OD_(600))为0.8时固化效果最好,其强度相较其他浓度可提升20%~50%;在最佳菌液浓度0.8时,固化频次为5次时砒砂岩即可获得很好的强度以及抗水蚀性,总雨蚀损失量可降至固化前的10%。菌液浓度0.8时碳酸钙含量生成最多,且多为菱形块状的方解石相,分布更加密集,随着固化次数的增加,胶结及填充效果更好。[结论]细菌及其胞外聚合物(EPS)在MICP中作为成核位点,参与碳酸钙的定位以及生长,并提高了碳酸钙的稳定性;EPS与碳酸钙以及砒砂岩中的矿物形成分子间氢键,增强了碳酸钙的胶结性能,且进一步提高了砒砂岩的强度以及抗水蚀性。

[Objective]The aims of this study are to explore the effect of MICP solidified loose Pisha sandstone,and to provide solutions and theoretical basis for reducing soil erosion in Pisha sandstone area.[Methods]The effects of the bacterial solution concentration and curing frequency on the mechanical properties of MICP-cured Pisha sandstone and its resistance to water erosion were investigated at the macro-scale(penetration strength,rainfall erosion,etc),and the mechanism of water erosion resistance of Pisha sandstone-cured soil was revealed at the micro-scale(X-ray diffraction,scanning electron microscopy,Fourier transform infrared spectroscopy,thermal analysis).[Results]For the same curing time,when the concentration of the bacterial liquid(OD_(600))was 0.8,the curing effect was the best,and its strength was increased by 20%~50% compared to the other concentrations.When the optimal concentration of the bacterial liquid was 0.8 and the curing frequency was five times,the Pisha sandstone attained a good strength and water erosion resistance,and the total rain erosion soil loss was reduced to 10% of the amount before curing.When the bacterial liquid concentration was 0.8,the calcium carbonate content was the greatest,and most of the calcite phase occurred as rhombic blocks and were more densely distributed.With increase of curing time,the cementation and filling effects improved.[Conclusion]The bacteria and their extracellular polymeric substances(EPS)in the MICP acted as nucleation sites,were involved in calcium carbonate localization and growth and development,and improved the stability of the calcium carbonate.The EPS,organic matter,calcium carbonate,and Pisha sandstone minerals involved in the formation of the intermolecular hydrogen bonds and other functional groups enhanced the cementation capacity of the calcium carbonate and further improved the strength of the Pisha sandstone and its resistance to water erosion.