Research On The Physical And Mechanical Behaviors Of The Soft Clay Under MICP Technology

In recent years,Microbial Induced Carbonate Precipitation（MICP）as a new type of soil reinforcement technology,there is increasing research on it.This technology is the degradation of microorganisms to generate carbonate ions,combined with free calcium ions to form calcium carbonate precipitation with gelling properties.It can fill the pores between the soil particles and cement the dispersed soil particles to improve their engineering mechanical properties.This article uses the MICP reinforcement technology to strengthen the coastal soft clay.Taking curing time,nutrient solution concentration,bacterial solution concentration,ratio of bacterial solution to nutrient solution,ratio of reaction solution to soil,calcium source as influencing factors,density,water content,liquid-plastic limit,dry density,calcium carbonate content,micro-morphology,mineral crystal composition,shear strength,compressive properties were used as indicators to conduct an experimental research on the behaviors under the MICP technology for strengthening soft clay.The main contents and achievements of this article are as follows:（1）The analysis of physical properties and micro-structure of soft clay reinforced by MICP:During the action of MICP,the hydrolysis of urea consumes water,which reduces the water content.The formation of calcium carbonates cause the densities and dry densities to increase slightly,and the liquid-plastic limits and plastic indexes decrease.Spherical calcium carbonates and their diffraction peaks were observed by SEM and XRD experiments.Verify the mechanism of MICP to strengthen soft clay from micro perspectives.（2）The analysis of the shear strength of soft clay reinforced by MICP:The dry powder mixing method is used to strengthen the soft clay,and their shear strengths are improved compared with the mud-consolidated remolded soft clay.They are1.15-4.86 times of the mud-consolidated remolded soft clay.Increasing the number of maintenance days,increasing the concentration of bacterial solution,reducing the ratio of reaction solution to soil,selecting a concentration of nutrient solution of 1.5mol/L,a ratio of bacterial solution to nutrient solution of 1:1,and calcium acetate as a calcium source can all improve the shear strength of soft clay reinforced by MICP.The shear strength of the samples with the ratio of the reaction solution to the remolded soft clay of 10%is 43%higher than that of the original remolded soft clay.（3）The analysis of the compression performance of soft clay reinforced by MICP:The dry powder is mixed with the reaction liquid for reinforcement.After curing,the compression performance of the soft clay is lower than that of the mud-consolidated remolded soft clay.The compression coefficient a_1-2can be reduced by 13.72%,and E_S,1-2can be increased by 6.95%.Factors such as reaction ages,biological reactants,catalyst,etc.all affect the compression performance.Compared with the original remolded soft clay,the reinforced remolded soft clay reduced a_1-2value by 5.16%,E_S,1-2increased by 6.04%,and the compression performance are improved.（4）There are certain correlations between the physical indexes and mechanical indexes of the soft clay reinforced by MICP,so that the mechanical indexes can be predicted by simple physical indexes.The above research show that MICP technology can effectively improve the physical and mechanical properties of soft clay,and provide theoretical supports for the application of MICP technology to strengthen soft clay in practical engineering.