Experimental Study On Mechanical Characteristics Of Silt With Different Cementation Degree Of Microbial Solidified Silt

Microbial induced calcium carbonate precipitation?MICP?technology is one of the technologies with good development prospects in the research of ground treatment technology.It is a new green foundation reinforcement method.Spraying,infiltration,grouting and other methods are used to mix Sporosarcina pasteurii and cement solution to rapidly precipitate CaCO₃ crystals.It can fill fine pores,form a structural skeleton.MICP can effectively cement loose particles,greatly improve the strength of the bulk material.MICP has been used for cementing of sand particles and achieved some success.Now this technology begins to expand into the field of fine-grained soil such as reinforced silt and clay.Based on the GDS triaxial test system,this paper conducts an experimental study on the static and dynamic properties of the MICP solidified silt.The combination of different grouting parameters is used to control the degree of cementation.The two-way cementing and mixing microbial liquid technology is used to effectively solve the uneven problems.Studying the influence of the clay on the mechanical properties of grouting and solidification,and studying the static and dynamic properties of MICP solidified silt with different degrees of cementation,provided a theoretical basis for the application of this technology.The two-way cementing and mixing microbial liquid technology is used to effectively solve the uneven problems.The experiment was carried out by changing the parameters of grouting round and cement concentration,and the effects of different fine particle content on CaCO₃ production and unconfined compressive strength were analyzed.Under the same grouting conditions,the samples of silt soil with no clay has low calcium carbonate formation but the highest strength.The primary clay soil has more calcium carbonate but low effective strength due to adsorption.In order to further study on the intensity evolution law of the intensity threshold,the degree of cementation was quantitatively controlled by using 0.25mol/L two-way grouting test,and the degree of cementation was evaluated according to the amount of CaCO₃ and the unconfined compressive strength.For the soil samples with different degrees of cementation,the Consolidation without drainage CU static triaxial test was carried out.Three kinds of fine particle components,four degrees of cementation,and three confining pressures?100 kPa,200 kPa,400 kPa?were studied for soil statics.The results show that the dilatancy of the samples leads to the occurrence of negative pore water pressure.The samples with low cementation level under high confining pressure has large axial strain,and the corresponding axial strain value of the negative pore pressure is larger.The amount of decline is large;the deformation mode of the samples with low cementation is mostly bulging failure,and the strain softening is not obvious;the axial strain of the samples under low confining pressure and high cementation level is small,and the axial strain value corresponding to the occurrence of negative pore pressure is higher.will show obvious shear band,showing obvious strain softening trend;by analyzing the peak strength and residual strength parameters,it is found that the mechanical properties of the MICP cemented silt mainly improve the cohesion of the samples,cementation The higher the degree,the greater the increase in cohesion.The Duncan model can accurately simulate the stress-strain curve of weakly cemented specimens,which has limitations on the simulation of softening curves of high cementation specimens.The results of the undrained CU dynamic triaxial test at 60 kPa effective confining pressure,initial shear stress ratio 0.5 and initial frequency 1 Hz show that the kinetic properties of the unbonded and weakly cemented samples in the four cementation grades is great influenced by the granular components,the kinetic properties are similar,and the resistance to deformation and liquefaction is weak.When the degree of cementation changes from weak cement to moderate and severe cementation,the kinetic properties are obviously changed,and the liquefaction resistance is greatly improved.The structure is remarkable and the samples is not easily liquefied.