Experimental Study On Soil Reinforcement Based On Denitrifying MICP

In recent years,microbially induced carbonate precipitation(MICP)technology has been widely used in the fields of foundation reinforcement,concrete repair and biological blocking in construction projects in my country because of its advantages of greenness and energy saving.On the basis of the existing MICP reinforcement technology,the denitrification MICP reinforcement experiment were carried out to study the soil reinforcement performance of the denitrification MICP technology which has a great significance for the MICP technology.Based on the denitrification MICP reinforcement technology,the soil samples with five fine-grained soil proportions(20%,30%,40%,50%,and 60%)were respectively strengthened by mixing method and adsorption method in this study,and unconfined compression test and direct shear test were performed to obtain the macroscopic mechanical properties of denitrified MICP-reinforced soil.Scanning electron microscopy(SEM)and X-ray diffraction(XRD)analysis were used to explore the microscopic mechanism of denitrified MICP-reinforced soil,that compared with Bacillus pasteuri MICP.On the basis of the above experiments,incorporating polypropylene fibers and wood fibers were added into the soil to verifiy the performance of denitrifying MICPreinforced soil furtherly.The results of the study are as follows:(1)Soil samples with the proportion of five kinds of fine-grained soil(20%～60%)were reinforced with denitrifying bacteria respectively,When the proportion of fine-grained soil in the sample is low,the reinforcement effect of denitrifying bacteria is weaker than that of Bacillus pasteurii.With the increase of the proportion of fine-grained soil,the reinforcement effect of denitrifying bacteria gradually exceeds that of Bacillus pasteuri.Denitrifying bacteria can increase the compressive strength of soil samples by 41.5% to 55.2% when using the adsorption method to reinforce the soil,and can increase the shear strength by about 30% when using the mixing method to reinforce the soil samples.(2)SEM technology and XRD technology were used to analyze the mechanism of MICP reinforcement of soil samples,it is shown that the deposition mode of calcium carbonate between soil particles is mainly due to the following:(1)Calcium carbonate precipitation exists in the form of overlaid soil particles.(2)Calcium carbonate precipitates to form connections between soil particles(3)The specimens of adding polypropylene fiber and wood fiber into the MICPreinforced sample were prepared,and through the relevant mechanical test,it is determined that when the optimal content of polypropylene is 0.3%,the ability to improve the reinforcement effect of MICP is the best,which can increase the compressive strength by1.22 times and the shear strength by 0.35 times,respectively.And it is determined that when the doping amount is 0.4 %,the compressive strength can be increased by 0.31 times and the shear strength can be increased by 0.11 times.