【Objective】 Determining the behavior of microbial cementation silt treated by bio-grouting, based on the technology of microbial induced carbonate precipitation(MICP), could provide a basis for developing the MICP technology and applying it for dredger fill silt. 【Method】 Experiments were conducted for cement dredger fill silt specimens by microbial grouting. Unconfined compressive tests, X-ray diffraction analyses(XRD), scanning electron microscope(SEM)observations, mercury intrusion porosimetry(MIP)and some chemical analyses were performed to investigate the difference in strength, mineral component, cementing CaCO3 content, soil microstructure and pore size distribution of untreated and treated dredger fill silts. 【Result】 After injecting 1 to 6 rounds of Sporosarcina pasteurii(A600=1.2)and a cement solution containing a mixture of CaCl2 and urea(0.1 mol/L)under constant pressure, the unconfined compressive strength of the treated silt specimens increased by 26.8%, 33.0%, 36.4%, 39.6%, 59.8% and 61.8% after the rounds 1 to 6, respectively, compared to the untreated silt specimen. The strength of the treated silt specimens increased with the number of rounds of injection. The cementing CaCO3 from the microbial grouting was mostly in the calcite phase, which filled the soil pores and cemented the soil particles. The CaCO3 content had a dominant effect on the strength of the treated silt. The more the CaCO3 precipitated from the microbial process in the silt, the higher was the strength of the silt. Furthermore, there was a sensitive threshold for CaCO3 content with respect to strength variation. The cementing efficiency increased significantly when the CaCO3 content was higher than the threshold, which varied with the genetic type or sedimentary environment of the silt. Compared to the untreated silt, the treated silt had significantly different pore diameter distribution characteristics. After the bio-grouting treatment, the pores in the range 10-300 μm in the silt reduced sharply, and the pores smaller than 10 μm remained almost unchanged. 【Conclusion】 Bio-grouting is an effective method that can be applied for cementing dredger fill silt. The strength of the dredger fill silt treated with microbial grouting is influenced by the CaCO3 content, and there is a sensitivity threshold for CaCO3 content with respect to strength variation. The pore size of the dredger fill silt is large enough for the microbial cells of Sporosarcina pasteurii migration. In the dredger fill silt treated by bio-grouting, there is a large reduction in the number of pores with a size over 10 μm.
{{custom_sec.title}}
{{custom_sec.title}}
{{custom_sec.content}}
References
[1] MITCHELL J K, SANTAMARINA J C. Biological considerations in geotechnical engineering[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2005, 131(10): 1222-1233.DOI:10.1061/(ASCE)1090-0241(2005)131:10(1222).
[2] LI B. Geotechnical properties of biocement treated soil[D]. Singapore: Nanyang Technological University, 2014.
[3] VAN PAASSEN L A, HARKES M P, VAN ZWIETEN G A, et al. Scale up of biogrout: a biological ground reinforcement method[C]// Hamza H, Shahlen M, Elmossalamy Y. Proceedings of the 17th International Conference on Soil Mechanics and Geotechnical Engineering. Lansdale: IOS Press, 2009:2328-2333.DOI: 10.3233/978-1-60750-031-5-2328.
[4] SOON N W, LEE L M, TAN C K, et al. Factors affecting improvement in engineering properties of residual soil through microbial-induced calcite precipitation[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2014, 140(5): 1-11.DOI: 10.1061/(ASCE)GT.1943-5606.0001089.
[5] 许朝阳, 张莉, 周健. 微生物改性对粉土某些特性的影响[J]. 土木建筑与环境工程, 2009, 31(2): 80-84. XU Z Y, ZHANG L, ZHOU J. Effect of microorganism on some engineering properties of silt[J]. Civil Engineering and Environmental Engineering,2009, 31(2): 80-84.DOI:10.3969/j.issn.1674-4764.2009.02.015.
[6] DEJONG J T, SOGA K, KAVAZANJIAN E, et al. Biogeochemical processes and geotechnical applications: progress, opportunities and challenges[J]. Géotechnique, 2012, 63(4):1-4.DOI:10.1680/geot.SIP13.P.017.
[7] 钱春香, 王安辉, 王欣. 微生物灌浆加固土体研究进展[J]. 岩土力学, 2015, 36(6):1537-1548.DOI:10.16285/j.rsm.2015.06.003. QIAN C X, WANG A H, WANG X. Advance of soilimprovement with bio-grouting[J]. Rock and Soil Mechanics, 2015, 36(6):1537-1548.
[8] STABNIKOV V, IVANOV V, CHU J. Construction Biotechnology: a new area of biotechnological research and applications[J]. World Journal of Microbiology and Biotechnology, 2015, 31(9):1303-1314.DOI:10.1007/s11274-015-1881-7.
[9] 许朝阳, 张莉. 微生物改性对粉土强度的影响[J]. 建筑科学, 2009, 25(5): 45-48.DOI: 10.13614/j.cnki.11-1962/tu.2009.05.011. XU Z Y, ZHANG L. The effect of microbes onstrength of silt[J]. Building Science, 2009, 25(5): 45-48.
[10] SOON N W, LEE L M, TAN C K, et al. Improvements in engineering properties of soils through microbial-induced calcite precipitation[J]. KSCE Journal of Civil Engineering, 2013, 17(4):718-728.DOI:10.1007/s12205-013-0149-8.
[11] REBATA LANDA V. Microbial activity in sediments: effects on soil behavior [D]. GA, USA: Civil and Environmental Engineering, Georgia Institute of Technology, 2007.
[12] WHIFFIN V S. Microbial CaCO3 precipitation for the production of Biocement[D]. Western Australia: Murdoch University, 2004.
[13] MORTENSEN B M, HABER M J, DEJONG J T, et al. Effects of environmental factors on microbial induced calcium carbonate precipitation[J]. Journal of Applied Microbiology, 2011, 111(2):338-49.DOI:10.1111/j.1365-2672.2011.05065.x.
[14] GONZALEZMUNOZ M T, RODRIGUEZNAVARRO C, MARTINEZRUIZ F, et al. Bacterial biomineralization: new insights from Myxococcus-induced mineral precipitation[J]. Geological Society London Special Publications, 2010, 336(1):31-50. DOI: 10.1144/SP336.3.
[15] DHAMI N K, REDDY M S, MUKHERJEE A. Biomineralization of calcium carbonates and their engineered applications: a review.[J]. Frontiers in Microbiology, 2013, 4:314-314.DOI:10.3389/fmicb.2013.00314.
[16] DEJONG J T, FRITZGES M B, NÜSSLEIN K. Microbially induced cementation to control sand response to undrained shear[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2006, 132(11):1381-1392.DOI: 10.1061/(ASCE)1090-0241(2006)132:11(1381).
[17] LEE L M, SOON N W, TANAKA Y. Stress-deformation and compressibility responses of bio-mediated residual soils[J]. Ecological Engineering, 2013, 60(6):142-149.DOI:10.1016/j.ecoleng.2013.07.034.
PDF(2348377 KB)
