不同方解石含量微生物胶结砂体细观损伤研究
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摘要
微生物胶结砂体是一种新型绿色建筑材料,方解石是微生物胶结砂的主要矿化成分.为探究方解石含量对微生物胶结材料细观损伤特性的影响,开展微生物胶结砂体固化试验.以典型工况下微生物胶结砂体为样本,借助基于矩张量的声发射模拟算法,嵌入能量监测程序,基于离散单元法建立颗粒流数值模型,开展不同方解石含量的微生物胶结砂数值模拟研究.研究表明:随矿化产物方解石含量的提升,微生物胶结砂强度逐渐升高,荷载作用下微裂纹数增多且分布趋于密集,最终破坏形态均为拉剪复合破坏模式,不同形式能量耗散程度随之加强.不同方解石含量胶结试样峰值应力前主要表现为能量存储和缓慢耗散的特性,峰值应力后主要是能量释放的过程.试样破裂后的矩震级分布与破裂形态有着紧密的对应关系,利用矩震级分布可以较好地判定胶结试样裂纹的萌生及扩展交汇区域.声发射频率与破裂强度呈正态分布,声发射破裂强度在-6.7左右时具有较高的声发射频率,最高频率在0.16左右;声发射次数与微裂纹数呈负指数函数关系,单次声发射事件中产生的微裂纹数增多时,事件发生的次数逐渐减少.研究成果可以有效弥补现有技术手段对新型微生物建筑材料研究的不足,并为进一步深入研究提供一种有效的新方法.
Microbial cemented sand is a novel green building material. Its main mineralized component is calcite. The solidification test of microbial cemented sand was performed,the microbial cemented sand under typical working conditions was taken as a sample,and an acoustic emission simulation algorithm based on moment tensor was used.Energy monitoring program was embedded,and the particle flow numerical model was established for the numerical simulation of microbial cemented sand with different calcite contents to explore the effect of calcite content on the mesodamage characteristic of the test material. Several main research results were obtained as follows:As the calcite content of mineralized products increased,the strength of the microbial cemented sand gradually increased,the number of microcracks increased and presented dense distribution under loading,and tensile–shear composite failure modes were the ultimate failure modes,the energy dissipation of different forms increases accordingly. Energy storage and slow dissipation were the main characteristics before peak stress. Postpeak stress was mainly involved in energy release. The moment magnitude distribution of samples was closely related to fracture morphology,and it can be used to determine the intersection area of crack initiation and propagation. Acoustic emission frequency and rupture strength were normally distributed,and high acoustic emission frequency existed when acoustic emission rupture strength is about-6.7. The highest frequency fell in the range of 0.16. The numbers of acoustic emission and microfracture were negative exponential functions,and as the number of microcracks in a single acoustic emission event increased,the number of events gradually decreased. Research results can effectively compensate for the shortcomings of existing technical approaches for research on novel microbial building materials and provide an effective new method for future research.
Microbial cemented sand is a novel green building material. Its main mineralized component is calcite. The solidification test of microbial cemented sand was performed,the microbial cemented sand under typical working conditions was taken as a sample,and an acoustic emission simulation algorithm based on moment tensor was used.Energy monitoring program was embedded,and the particle flow numerical model was established for the numerical simulation of microbial cemented sand with different calcite contents to explore the effect of calcite content on the mesodamage characteristic of the test material. Several main research results were obtained as follows:As the calcite content of mineralized products increased,the strength of the microbial cemented sand gradually increased,the number of microcracks increased and presented dense distribution under loading,and tensile–shear composite failure modes were the ultimate failure modes,the energy dissipation of different forms increases accordingly. Energy storage and slow dissipation were the main characteristics before peak stress. Postpeak stress was mainly involved in energy release. The moment magnitude distribution of samples was closely related to fracture morphology,and it can be used to determine the intersection area of crack initiation and propagation. Acoustic emission frequency and rupture strength were normally distributed,and high acoustic emission frequency existed when acoustic emission rupture strength is about-6.7. The highest frequency fell in the range of 0.16. The numbers of acoustic emission and microfracture were negative exponential functions,and as the number of microcracks in a single acoustic emission event increased,the number of events gradually decreased. Research results can effectively compensate for the shortcomings of existing technical approaches for research on novel microbial building materials and provide an effective new method for future research.
引文
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[18]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 Xiaohui,Ma Qiang,Yang Zuan,et al.Dynamic response of liquefiable sand foundation improved by bio-grouting[J].Chinese Journal of Geotechnical Engineering,2013,35(8):1486-1495(in Chinese).
[19]Li B.Geotechnical Properties of Biocement Treated Soils[D].Singapore:Nanyang Technological University,2014.
[20]Cundall P A.The Measurement and Analysis of Accelerations in Rock Slopes[D].London:University of London,1971.
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[23]Zhao X L,Evans T M.Discrete simulations of laboratory loading conditions[J].International Journal of Geomechanics,2009,9(4):169-178.
[24]Evans T M,Khoubani A,Montoya B M.Simulating mechanical response in biocemented sands[J].Computer Methods and Recent Advances in Geomechanics,2014(9):1569-1574.
[25]Wang Y H,Leung S C.A particulate-scale investigation of cemented sand behavior[J].Canadian Geotechnical Journal,2008,45(1):29-44.
[26]Feng K,Montoya B M.Influence of confinement and cementation level on the behavior of microbial-induced calcite precipitated sands under monotonic drained loading[J].Journal of Geotechnical and Geoenvironmental Engineering,2016,142(1):04015057.
[27]Barkouki T H,Martinez B C,Mortensen B M,et al.Forward and inverse bio-geochemical modeling of microbially induced calcite precipitation in half-meter column experiments[J].Transport in Porous Media,2011,90(1):23-39.
[28]Xu G,Tang Y,Lian J,et al.Mineralization process of biocemented sand and impact of bacteria and calcium ions concentrations on crystal morphology[J].Advances in Materials Science&Engineering,2017(19):1-13.
[29]Tang Y,Xu G,Yan Y,et al.Thermal cracking analysis of microbial cemented sand under various on DEMmethod[J].Advances in Materials Science&Engineering,2018(4):1-15.
[30]Potyondy D O,Cundall P A.A bonded-particle model for rock[J].International Journal of Rock Mechanics and Mining Sciences,2004,41(8):1329-1364.
[31]Feng K,Montoya B M,Evans T M.Discrete element method simulations of bio-cemented sands[J].Computers&Geotechnics,2017,85:139-150.
[32]Wang Y H W H,Leung S C L C.A particulate-scale investigation of cemented sand behavior[J].Canadian Geotechnical Journal,2008,45(1):29-44.
[33]Tang Y,Xu G,Qu C,et al.Damage simulation of a random aggregate model induced by microwave under different discontinuous ratios and exposure times[J].Advances in Materials Science and Engineering,2016,2016:5690272.
[34]Hazzard J F,Young R P.Moment tensors and micromechanical models[J].Tectonophysics,2002,356(1):181-197.
[35]Bieniawski Z T.Mechanism of brittle fracture of rock:Part I-Theory of the fracture process[J].International Journal of Rock Mechanics&Mining Sciences&Geomechanics Abstracts,1967,4(4):395-406.
[36]蒋明镜,张望城,王剑锋.密实散粒体剪切破坏能量演化的离散元模拟[J].岩土力学,2013,34(2):551-558.Jiang Mingjing,Zhang Wangcheng,Wang Jianfeng.Energy evolution of dense granules subjected to shear failure by discrete element method[J].Rock and Soil Mechanics,2013,34(2):551-558(in Chinese).
[2]Van Paassen L A.Biogrout,Ground Improvement by Microbial Induced Carbonate Precipitation[D].Delft:Delft University of Technology,2009.
[3]Cheng L,Shahin M A,Mujah D.Influence of key environmental conditions on microbially induced cementation for soil stabilization[J].Journal of Geotechnical&Geoenvironmental Engineering,2016,143(1):1-11.
[4]Qian C X,Pan Q F,Wang R X.Cementation of sand grains based on carbonate precipitation induced by microorganism[J].Science China Technological Sciences,2010,53(8):2198-2206.
[5]Al Qabany A,Soga K,Santamarina C.Factors affecting efficiency of microbially induced calcite precipitation[J].Journal of Geotechnical and Geoenvironmental Engineering,2011,138(8):992-1001.
[6]Chu J,Ivanov V,Naeimi M,et al.Optimization of calcium-based bioclogging and biocementation of sand[J].Acta Geotechnica,2014,9(2):277-285.
[7]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):338-349.
[8]Qabany A A,Soga K,Santamarina C.Factors Affecting efficiency of microbially induced calcite precipitation[J].Journal of Geotechnical&Geoenvironmental Engineering,2012,138(8):992-1001.
[9]Okwadha G,Li J.Optimum conditions for microbial carbonate precipitation[J].Chemosphere,2010,81(9):1143-1148.
[10]Ng W S,Lee M L,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.
[11]Oliveira P J V,Freitas L D,Carmona J P S F.Effect of soil type on the enzymatic calcium carbonate precipitation process used for soil improvement[J].Journal of Materials in Civil Engineering,2016,29(4):1-7.
[12]Whiffin V S,van Paassen L A,Harkes M P.Microbial carbonate precipitation as a soil improvement technique[J].Geomicrobiology Journal,2007,24(5):417-423.
[13]Martinez B C,Dejong J T,Ginn J,et al.Experimental optimization of microbial-induced carbonate precipitation for soil improvement[J].Journal of Geotechnical&Geoenvironmental Engineering,2013,139(4):587-598.
[14]Harkes M P,Paassen L A V,Booster J L,et al.Fixation and distribution of bacterial activity in sand to induce carbonate precipitation for ground reinforcement[J].Ecological Engineering,2010,36(2):112-117.
[15]Zhao Q,Li L,Li C,et al.Factors affecting improvement of engineering properties of MICP-treated soil catalyzed by bacteria and urease[J].Journal of Materials in Civil Engineering,2014,26(12):04014094.
[16]Paassen L A V,Ghose R,Linden T J M V D,et al.Quantifying bio-mediated ground improvement by ureolysis:A large scale biogrout experiment[J].Journal of Geotechnical&Geoenvironmental Engineering,2010,136(12):1721-1728.
[17]Dejong J T,Mortensen B M,Martinez B C,et al.Biomediated soil improvement[J].Ecological Engineering,2010,36(2):197-210.
[18]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 Xiaohui,Ma Qiang,Yang Zuan,et al.Dynamic response of liquefiable sand foundation improved by bio-grouting[J].Chinese Journal of Geotechnical Engineering,2013,35(8):1486-1495(in Chinese).
[19]Li B.Geotechnical Properties of Biocement Treated Soils[D].Singapore:Nanyang Technological University,2014.
[20]Cundall P A.The Measurement and Analysis of Accelerations in Rock Slopes[D].London:University of London,1971.
[21]Cundall P A.A computer model for simulating progressive large scale movements in blocky rock systems[C]//Proceedings of the International Symposium on Rock Mechanics.Nancy,France,1971:129-136.
[22]Jacobson D E,Valdes J R,Evans T M.A numerical view into direct shear specimen size effects[J].Geotechnical Testing Journal,2007,30(6):512-516.
[23]Zhao X L,Evans T M.Discrete simulations of laboratory loading conditions[J].International Journal of Geomechanics,2009,9(4):169-178.
[24]Evans T M,Khoubani A,Montoya B M.Simulating mechanical response in biocemented sands[J].Computer Methods and Recent Advances in Geomechanics,2014(9):1569-1574.
[25]Wang Y H,Leung S C.A particulate-scale investigation of cemented sand behavior[J].Canadian Geotechnical Journal,2008,45(1):29-44.
[26]Feng K,Montoya B M.Influence of confinement and cementation level on the behavior of microbial-induced calcite precipitated sands under monotonic drained loading[J].Journal of Geotechnical and Geoenvironmental Engineering,2016,142(1):04015057.
[27]Barkouki T H,Martinez B C,Mortensen B M,et al.Forward and inverse bio-geochemical modeling of microbially induced calcite precipitation in half-meter column experiments[J].Transport in Porous Media,2011,90(1):23-39.
[28]Xu G,Tang Y,Lian J,et al.Mineralization process of biocemented sand and impact of bacteria and calcium ions concentrations on crystal morphology[J].Advances in Materials Science&Engineering,2017(19):1-13.
[29]Tang Y,Xu G,Yan Y,et al.Thermal cracking analysis of microbial cemented sand under various on DEMmethod[J].Advances in Materials Science&Engineering,2018(4):1-15.
[30]Potyondy D O,Cundall P A.A bonded-particle model for rock[J].International Journal of Rock Mechanics and Mining Sciences,2004,41(8):1329-1364.
[31]Feng K,Montoya B M,Evans T M.Discrete element method simulations of bio-cemented sands[J].Computers&Geotechnics,2017,85:139-150.
[32]Wang Y H W H,Leung S C L C.A particulate-scale investigation of cemented sand behavior[J].Canadian Geotechnical Journal,2008,45(1):29-44.
[33]Tang Y,Xu G,Qu C,et al.Damage simulation of a random aggregate model induced by microwave under different discontinuous ratios and exposure times[J].Advances in Materials Science and Engineering,2016,2016:5690272.
[34]Hazzard J F,Young R P.Moment tensors and micromechanical models[J].Tectonophysics,2002,356(1):181-197.
[35]Bieniawski Z T.Mechanism of brittle fracture of rock:Part I-Theory of the fracture process[J].International Journal of Rock Mechanics&Mining Sciences&Geomechanics Abstracts,1967,4(4):395-406.
[36]蒋明镜,张望城,王剑锋.密实散粒体剪切破坏能量演化的离散元模拟[J].岩土力学,2013,34(2):551-558.Jiang Mingjing,Zhang Wangcheng,Wang Jianfeng.Energy evolution of dense granules subjected to shear failure by discrete element method[J].Rock and Soil Mechanics,2013,34(2):551-558(in Chinese).