Experimental Study on Microstructure Evolution and Fractal Features of Expansive Soil Improved by MICP Method

Su, Huanyu; Xiao, Hongbin; Li, Zhenyu; Tian, Xuwen; Luo, Shenping; Yu, Xinpei; Ouyang, Qianwen

doi:10.3389/fmats.2022.842887

Cited by 10 publications

(3 citation statements)

References 44 publications

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“…According to the existing studies in our group, it was found that the best improvement of soil samples was achieved at a volume ratio of 1:2 between the bacterial solution and the cementation solution in the MICP process (Tian et al, 2022;Su et al, 2022). Therefore, the volume ratio of bacterial solution to cementation solution per unit mass of soil sample was controlled to 1:2.…”

Section: Preparation Of Specimensmentioning

confidence: 99%

A Fractional Order Creep Damage Model for Microbially Improved Expansive Soils

Tian

Xiao

et al. 2022

Front. Earth Sci.

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Microbial Induced Calcite Precipitation method was used to improve the expansive soils of Nanning, Guangxi. The nonlinear shear creep behavior of microbially improved expansive soil was studied by triaxial consolidation drainage shear test. The results show that when the expansive soil was applied a small partial stress, the creep curve of soil exhibits transient deformation and decay creep. When the partial stress reaches a certain value, there is decay creep, steady-state creep and accelerated creep successively showed on the creep curve. The stress-strain isochronous curves reflect there are obvious nonlinear characteristics in the creep process of improved expansive soils. The degree of this nonlinearity is related to the creep time and stress level. The longer the creep time as well as the higher the stress level, the higher the degree of nonlinearity. Based on the fractional calculus theory and statistical damage theory, the probability density function of Weibull distribution was introduced, and the damage degradation of soft component viscosity coefficient was considered. As a result, a fractional-order damage creep model which can describe the shear creep evolution of microbially improved expansive soils is established. Compared with the Kelvin creep model of integer order and the Burgers creep model of fractional order, the fractional order damage creep model has not only better comparative evaluation results but also more higher computational accuracy. It indicates that the fractional-order damage creep model can better describe the whole process of shear creep in microbially improved expansive soils. The above findings provide a theoretical basis for the study of deformation analysis of microbially improved expansive soils under long-term loading.

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Section: Preparation Of Specimensmentioning

confidence: 99%

A Fractional Order Creep Damage Model for Microbially Improved Expansive Soils

Tian

Xiao

et al. 2022

Front. Earth Sci.

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“…The experimental study of using microorganisms to improve unfavorable soil makes it possible to apply this method to engineering. Scholars have used MICP technology to improve unfavorable soil to varying degrees, including sand [ 40 , 41 , 42 ], silt [ 43 , 44 , 45 ], loess [ 46 , 47 , 48 , 49 , 50 ], expansive soil [ 51 , 52 , 53 , 54 ], and mucky soil [ 55 , 56 ], using this method, and the unconfined compressive strength and cohesion of the soil are significantly improved, which can be used in engineering practice. In the field of geotechnical engineering, the research results of MICP on soil improvement can be used for foundation reinforcement [ 57 , 58 , 59 ], earth dam reinforcement [ 60 ], wind prevention, sand fixation [ 61 ], reservoir bottom anti-seepage, and anti-seepage curtains [ 42 ].…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Silt Soil Improved by Microbial Solidification with the Use of Lignin

Sun

Zhong

et al. 2023

Microorganisms

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At present, in the field of geotechnical engineering and agricultural production, with increasingly serious pollution an environmentally friendly and efficient means is urgently needed to improve the soil mass. This paper mainly studied the microbial induced calcium carbonate precipitation (MICP) technology and the combined effect of MICP technology and lignin on the improvement of silt in the Beijing area. Through unconfined compressive strength and dynamic triaxial test methods, samples improved by microorganisms were studied to obtain the optimal values of cement concentration and lignin under these two test schemes. The results show that after the incubation time of Sporosarcina pasteurii reached 24 h, the OD600 value was 1.7–2.0 and the activity value (U) was 930–1000 mM ms/min. In the unconfined static pressure strength test, after MICP treatment the optimal concentration of cementitious solution for constant temperature and humidity samples and constant-temperature immersion samples was 1.25 mol/L. The compressive strength of the constant temperature and humidity sample was 1.73 MPa, and the compressive strength of the constant-temperature immersion sample was 3.62 Mpa. At the concentration of 1.25 mol/L of cement solution, MICP technology combined with lignin could improve the constant temperature and humidity silt sample. The optimal addition ratio of lignin was 4%, and its compressive strength was 1.9 MPa. The optimal lignin addition ratio of the sample soaked at a constant temperature was 3%, and the compressive strength was 4.84 MPa. In the dynamic triaxial multi-stage cyclic load test, the optimal concentration of cementation solution for the constant temperature and humidity sample after MICP treatment was 1.0 mol/L, and the failure was mainly inclined cracks. However, in the condition of joint improvement of MICP and lignin, the sample mainly had a drum-shaped deformation, the optimal lignin addition ratio was 4%, and the maximum axial load that the sample could bear was 306.08 N. When the axial dynamic load reached 300 N, the strain accumulation of the 4% group was only 2.3 mm. In this paper, lignin, an ecofriendly material, was introduced on the basis of MICP technology. According to the failure shape and relevant results of the sample, the addition of lignin was beneficial for the improvement of the compressive strength of the sample.

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“…As a new foundation reinforcement method, microbially induced calcite precipitation (MICP) technology has a potential application value in the fields of liquefiable sand layers (Riveros and Sadrekarimi, 2020), roadbeds (Xiao et al, 2022), and foundation pit slope reinforcement (Cheng et al, 2021). Compared with the traditional cement reinforcement method, the MICP treatment method is environmentally friendly, has low energy consumption, and is sustainable (Wang et al, 2017;Castro-Alonso et al, 2019;Su et al, 2022). In island construction, compared to traditional cement solidification, MICP has two major advantages: the first is the abundant Cl − and SO 4 2in the marine environment that will cause corrosion to ferroconcrete but have little impact on MICP treatment (Saleem et al, 1996); the second is the slightly alkaline environment of the ocean that is conducive to the reaction of microorganisms (Stocks-Fischer et al, 1999).…”

mentioning

confidence: 99%

Experiment on MICP-solidified calcareous sand with different rubber particle contents and sizes

Xu,

Yan

2024

Front. Mater.

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Microbially induced calcite precipitation (MICP) is a new environmentally friendly technology, with the ability to improve the mechanical properties of calcareous sand. Rubber is a high-compressibility material with a higher damping ratio than that of calcareous sand. In this study, calcareous sand was replaced by equal volume contents (0%, 1%, 3%, 5%, 7%, and 9%) and different sizes (0–1, 1–2, and 2–3 mm) of rubber, and a series of water absorption and unconfined compressive strength (UCS) tests were conducted on MICP-solidified rubber–calcareous sand (MRS). The results showed that the water absorption is reduced when the rubber content is larger. The UCS of 0–1-mm MRS decreased with the increase in rubber content. For 1–2-mm and 2–3-mm MRS, the UCS was improved by 11.30% and 15.69%, respectively, compared with the clean sand. Adding rubber promoted the formation of calcium carbonate, but the strength and stiffness of rubber particles were lower than those of the calcareous sand. Therefore, higher rubber content weakened the sand frame bearing system, and the UCS decreased when the rubber content was more than 5%. Moreover, a large amount of 0–1-mm rubber led to the increase in transverse deformation of the samples, which caused the acceleration of the destruction of the sand structure. The water absorption of 0–1-mm MRS was higher than that of 1–2-mm and 2–3-mm MRS, but the UCS of 0–1-mm MRS was lower. The best rubber size is 1–2 mm and 2–3 mm, and the best rubber content is 3%–5%. The outcome of this study may, in the authors’ view, prove beneficial in improving the strength of calcareous sand when it is reinforced by MICP-combined rubber.

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Experimental Study on Microstructure Evolution and Fractal Features of Expansive Soil Improved by MICP Method

Cited by 10 publications

References 44 publications

A Fractional Order Creep Damage Model for Microbially Improved Expansive Soils

A Fractional Order Creep Damage Model for Microbially Improved Expansive Soils

Experimental Study on Silt Soil Improved by Microbial Solidification with the Use of Lignin

Experiment on MICP-solidified calcareous sand with different rubber particle contents and sizes

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