| Based on the mineralization of microorganisms,the improvement effect of MICP technology on the mechanical properties of coarse-grained Soil mechanics was explored by using the method of microbial induced carbonate deposition to form cementation between particles.The process of MICP cementation of coarse-grained soil is influenced by many factors,mainly studying the influence of MICP on the mechanical properties of coarse-grained soil cementation samples from three perspectives: concentration of cementation solution,particle size,and cementation cycle.The method is to use Bacillus pasteureus to catalyze the hydrolysis of urea and generate calcium carbonate with cementation between particles to prepare cementation samples.Through Direct shear test,unconfined compression test,scanning electron microscope test and X-ray diffraction test,the cementation effect of MICP technology on coarse soil samples is analyzed and studied.The main research results of this article are as follows:(1)The stress-strain curves of the cemented sand samples are all of strain softening type;Under the same normal stress,as the concentration of the binder increases,the shear strength of the sample gradually increases,and its internal friction angle shows a trend of first increasing and then slightly decreasing;As the bonding period increases,the cohesion of the sample gradually increases;When the bonding period is 14 or 21 days,the shear strength of samples with a particle size range of 1.18-2.0mm increases more significantly;When the bonding period is 7 days,the shear strength of the sample shows a trend of first increasing and then decreasing with the increase of particle size range.Moreover,when the particle size range is 0.6-1.18 mm,the shear strength of the sample is the highest.(2)By measuring the quality of calcium carbonate,it was found that the amount of calcium carbonate generated in cemented sand samples increases with the increase of cement concentration,particle size range,and cement cycle.When the cement concentration is 2mol/L,the growth rate of calcium carbonate production in the sample is the highest;Due to the limitation of pores in the cementation reaction of samples with a small particle size range,as the cementation period increases,the amount of calcium carbonate generated in samples with a larger particle size range is higher.Based on the analysis of mechanical test results,it is found that the amount of calcium carbonate generated in the bonded sample is positively correlated with its shear strength.(3)In the unconfined compressive strength test,the stress-strain curve of bonded sand samples can be divided into four stages: compaction stage,elastic stage,plastic stage,and failure stage;As the concentration of the binder increases,the compressive strength of the sample gradually increases,but its growth rate gradually decreases;When the cementation period is fixed,there is a significant difference in the compressive strength of samples with different particle sizes;When the bonding period is 7 days,the strength value of the sample with a particle size range of 0.6-1.18 mm is the highest;When the bonding period is 21 days,the sample with a particle size range of 1.18-2.0mm has the highest strength value.(4)The microstructure and phase composition of cemented sand samples were analyzed through microscopic experiments.As the concentration of the bonding solution and the bonding period increase,the amount of calcium carbonate crystals generated on the surface of the sample particles and between the particles increases,and the crystallinity of the calcium carbonate crystals generated in the sample increases,and the shape of the calcium carbonate crystals changes from a spherical shape to a relatively stable diamond shape;When the concentration of the bonding solution is 2.0mol/L,the largest crystal size of calcium carbonate is generated in the sample.Analysis shows that crystal size is the main factor affecting the variation of internal friction angle in the sample. |
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