微生物固化纤维加筋砂土抗剪强度试验研究
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摘要
微生物固化(MICP)技术能显著提高土体的抗剪强度,但微生物固化土体也存在脆性破坏特征显著的缺陷。向待固化砂土中掺入一定量的纤维,以改善微生物固化砂土的脆性破坏特性,并基于固结排水三轴试验研究了微生物固化纤维加筋砂土的抗剪强度特性,在此基础上探讨胶结次数、纤维含量、纤维长度以及试样初始相对密实度等参数对微生物固化纤维加筋砂土剪切特性的影响。最后,结合电镜扫描测试探究纤维加筋对微生物固化砂土剪切特性影响的内在机理。结果表明:MICP过程中,碳酸钙晶体能有效沉积在纤维表面,提高其表面粗糙度,且碳酸钙与砂的混合体能对纤维提供锚固作用,从而在一定程度上提高微生物固化砂土抗剪强度,并改善其应变软化特性,纤维具备改善微生物固化土体脆性破坏特征的潜力。
Microbial-induced calcite precipitation(MICP)has the prominent advantage of significant improving the shear strength of soil,while MICP sand also has the obvious shortcoming of brittle failure.A certain amount of fiber was added into MICP sand in order to improve the brittleness,and based on consolidated drained triaxial compression tests,the shear strength characteristics of fiber-reinforced biocemented sand was studied.And then,the effects of fiber content,fiber length and initial relative compactness of samples on the shear characteristics of fiber-reinforced bio-cemented sand were discussed.Finally,the corresponding mechanisms of strength enhancement and ductility improvement were also investigated through scanning electron microscope.The results show that during the process of MICP,calcium carbonate crystals deposited on the fiber surface effectively improve the roughness of fibers surface,while the mixture of calcium carbonate and sand provides anchorage to the fibers,enhancing the shear strength of MICP sand and improving the strain softening characteristic,and it is concluded that fiber has the potential to improve brittleness of MICP sand.
Microbial-induced calcite precipitation(MICP)has the prominent advantage of significant improving the shear strength of soil,while MICP sand also has the obvious shortcoming of brittle failure.A certain amount of fiber was added into MICP sand in order to improve the brittleness,and based on consolidated drained triaxial compression tests,the shear strength characteristics of fiber-reinforced biocemented sand was studied.And then,the effects of fiber content,fiber length and initial relative compactness of samples on the shear characteristics of fiber-reinforced bio-cemented sand were discussed.Finally,the corresponding mechanisms of strength enhancement and ductility improvement were also investigated through scanning electron microscope.The results show that during the process of MICP,calcium carbonate crystals deposited on the fiber surface effectively improve the roughness of fibers surface,while the mixture of calcium carbonate and sand provides anchorage to the fibers,enhancing the shear strength of MICP sand and improving the strain softening characteristic,and it is concluded that fiber has the potential to improve brittleness of MICP sand.
引文
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[2]DEJONG J T,MORTENSEN B M,MARTINEZ B C,et al.Bio-mediated soil improvement[J].Ecological Engineering,2010,36(2):197-210.
[3]YANG Z,CHENG X H,LI M.Engineering properties of MICP-bonded sandstones used for historical masonry building restoration[C]//GeoFrontiers Congress 2011,March 13-16,2011,Dallas,Texas,USA,2011.
[4]程晓辉,麻强,杨钻,等.微生物灌浆加固液化砂土地基的动力反应研究[J].岩土工程学报,2013,35(8):1486-1495.CHENG X H,MA Q,YANG Z,et al.Dynamic response of liquefiable sand foundation improved by biogrouting[J].Chinese Journal of Geotechnical Engineering,2013,35(8):1486-1495.(in Chinese)
[5]CUI M J,ZHENG J J,ZHANG R J,et al.Influence of cementation level on the strength behaviour of biocemented sand[J].Acta Geotechnica,2017,12(5):971-986.
[6]GRAY D H,AL-REFEAI T.Behavior of fabric-versus fiber-reinforced sand[J].Journal of Geotechnical Engineering,1986,112(8):804-820.
[7]YETIMOGLU T,SALBAS O.A study on shear strength of sands reinforced with randomly distributed discrete fibers[J].Geotextiles and Geomembranes,2003,21(2):103-110.
[8]SHAO W,CETIN B,LI Y D,et al.Experimental investigation of mechanical properties of sands reinforced with discrete randomly distributed fiber[J].Geotechnical and Geological Engineering,2014,32(4):901-910.
[9]LI M D,LI L,OGBONNAYA U,et al.Influence of fiber addition on mechanical properties of MICP-treated sand[J].Journal of Materials in Civil Engineering,2016,28(4):04015166.
[10]CHOI S G,WANG K J,CHU J.Properties of biocemented,fiber reinforced sand[J].Construction and Building Materials,2016,120:623-629.
[11]崔明娟,郑俊杰,赖汉江,等.菌液注射方式对微生物固化砂土动力特性影响试验研究[J].岩土力学,2017,38(11):3173-3178.CUI M J,ZHENG J J,LAI H J,et al.Effect of method of biological injection on dynamic behavior for bio-cemented sand[J].Rock and Soil Mechanics,2017,38(11):3173-3178.(in Chinese)
[12]南京水利科学研究院.土工试验方法标准:GB/T50123-1999[S].北京:中国计划出版社,1999.Nanjing Hydraulic Research Institute.Geotechnical test method standard:GB/T 50123-1999[S].Beijing:China Planning Press,1999.(in Chinese)