微生物追踪固结技术在堤防防渗中的应用

利用微生物固结对岩土体进行防渗加固,在安徽滁州大洼水库黏性土堤防3个区段开展防渗试验,通过培养巴氏芽孢杆菌对尿素进行水解产生大量碳酸根离子并和钙镁离子结合生成碳酸钙沉积,从而堵塞坝体内部孔隙/裂隙。利用坝体内部测压管对内部水头进行监测,同时监测渗漏部位的渗漏量,试验结果表明,该技术能迅速降低黏性土堤防坝段渗透系数2个数量级。整个试验过程中,试验段微生物固结过程分为3个主要阶段:0~80 h为微生物固结发展期; 80~120 h为高峰转折期; 120 h以后为封闭拖尾期。处理后土体渗透系数为10-5~10-6cm/s,同时土样平均强度提高约13%(不固结不排水剪切试验结果)。利用电子显微镜和EDS能谱仪对土体孔隙内部生成物进行成分检测,结果表明碳酸钙是其主要组成物质。

Study on application of microbial tracing consolidation technology in the seepage prevention of earth bank

Bio-clogging is a novel technology in soil seepage prevention and consolidation, and this technology was applied in 3 bank sections of Dawa Reservoir in Chuzhou, Anhui Province. Bacillus pasteurii was chosen as the agent to generate carbonate ions, which could precipitate with calcium/magnesium ions to clog pores and fractures inside the earth bank. In these applications, inside water heads were monitored using installed piezometers and the flow rate of leakage was also measured. Results showed that the reduction rate of the bank soil conductivity can reach 99% in a short time. The whole process of in-situ test can be divided into three main stages: 0-80 h is the development period of bio-clogging; 80-120 h is the peak period and then followed by the tailing period. The soil conductivities were around 10^-5-10^-6 cm/s after bio-clogging treatment, meanwhile the soil strength increased by 13% according to UU tests. Samples inside of the pores were detected using electronic microscope and EDS detector, and main composition was proved to be calcium carbonate.