粒径效应对大豆粗脲酶固化砂土效果的影响

Effect of grain size on biocementation of sand using crude soybean urease

基于大豆粗脲酶的生物固化技术是岩土工程领域新兴起的一种新型环保的地基处理技术,其固化均匀性是推进该技术在实际工程应用中亟待解决的一个重要问题,而土体粒径是其中一个重要影响因素。选取13种不同粒径的砂土并采用自提取的大豆粗脲酶液,通过开展脲酶渗滤试验、砂柱固化试验和扫描电镜测试,分析土体粒径效应对基于大豆粗脲酶固化砂土效果的影响,并对其影响机制进行探讨。研究结果表明:土体颗粒粒径对大豆粗脲酶液中脲酶的迁移与吸附有显著影响,土体粒径小有利于脲酶的吸附,但土体粒径过小(比如小于0.425mm)会导致大多吸附的脲酶集中在土体的中上部区域;土体粒径过大(比如大于4.750mm)则又不利于脲酶在土体的中上部区域吸附。两种工况均易导致生物固化不均匀。除脲酶吸附量外,土体粒径效应对基于大豆脲酶生物固化效果的影响还与土体内孔隙尺寸、单位土体内颗粒接触数等因素有关。土体粒径越大,颗粒间孔隙尺寸越大,颗粒接触数少,不利于有效碳酸钙晶体的形成。

Bio-cementation technology based on crude soybean urease is a new environmentally friendly foundation treatment technology emerging in the field of geotechnical engineering.The uniformity of bio-cementation is a pressing issue that needs to be addressed to advance the application of this technology in practical engineering,and soil particle size stands as a significant influencing factor.In this study,13 types of sand with varying particle sizes were selected,along with self-extracted crude soybean urease solution,to conduct urease percolation tests,sand column curing tests,and scanning electron microscope(SEM)examinations.These experiments aimed to analyze the influence of soil particle size on the effectiveness of bio-cementation using crude soybean urease and explore its underlying mechanisms.The findings reveal that soil particle size significantly affects the migration and adsorption of urease in the crude soybean urease solution.Smaller soil particle sizes facilitate the adsorption of urease.However,excessively small particle sizes(e.g.,less than 0.425 mm)lead to the concentration of most adsorbed urease in the middle and upper regions of the soil column.Conversely,excessively large particle sizes(e.g.,greater than 4.750 mm)hinder urease adsorption in these regions.Both scenarios tend to result in uneven bio-cementation.Besides the amount of urease adsorption,the influence of soil particle size effect on the biocementation efficacy based on soybean urease is also associated with factors such as pore size within the soil and the number of particle contacts per unit volume of soil.Larger soil particles result in larger interstitial pore sizes and fewer particle contacts,thus hindering the formation of effective calcium carbonate crystals.