Study On Microbiologically Induced Calcite Carbonate Precipitation To Repair And Cure The Cracks

The technology of microbiologically induced calcite carbonate precipitation was inspired by the phenomenon of bio-mineralization in nature. The mechanism is that the urease produced by microorganism can hydrolyze urea, then the product react with the calcium ions to form calcium carbonate which is soluble in water. Microbiologically induced calcium carbonate precipitation is pollution free and natural, and belongs to the material cycle of nature. At present, the application of microbiologically induced calcium carbonate precipitation is few, and most institutes do some research in the laboratory. Based on the present achievements, the field test was designed, then applied to an underground engineering.Bacillus pasteurii was used in this test, and the bacteria liquid was obtained by the 50L fermentation tank, which cost 18 hours, then the enzyme activity was measured. The initial pH of culture medium was adjusted to 9.0 by sodium hydroxide. The temperature of the fermentation was 30℃. The reaction liquid was a mixture of urea and calcium, and the concentration of which were 1mol/L. The main contents include as following:1. Before the field test, the condition survey and hydrogeological survey was carried out, and the width and distribution of cracks, concrete strength of walls, underground water lever, penetration of soil were grasped. Based on these, the filed test was carried out.2. Grouting soil with bacteria liquid and Urea-Ca(NO3)2 medium was used to analyze the influence of microbiologically induced calcium carbonate precipitation on penetration of soil, and the cracks leakage before and after testing was compared. The results show that the penetration of soil was obviously reduced, and the cracks got tilled.3. A filed test of repairing horizontal cracks by the trough was carried out. The action of the trough in repairing cracks was studied, and the cracks leakage before and after testing was analyzed. The results indicate that the trough can provide grouting pressure by liquid height and prevent mixture into the soil. The cracks were blocked at last.4. The test of repairing vertical cracks by the slant holes was earned out. The effects of slant holes on repairing cracks was analyzed, and the cracks leakage before and after testing was checkout. The results reveal that slant holes which was filled with calcium carbonate were found to work well, and the crack was blocks.5. Finally, brushing bacteria liquid and Urea-Ca(NO3)2 medium on the surface of the crack by turn were used for vertical cracks. It was found that with the increase of the number of brushwork, the deposited layer which bound with the surface tightly was formed.Generally, according to all the study it was proved to be feasible to apply the technology to practical project, and the shortcomings and defects of the technology in the process of the test were summarized, which direct the following research. More than that, the process of the field test were showed, and the methods of examining for field test were given.