Experimental Study On Solidifying Characteristics Of Granite Residual Soil By Concentration Of Cementing Fluid And Times Of Infusion

In the application of MICP technology for subgrade slope surface protection,it is important to study the microbial solidification characteristics of granite residual soils.In this paper,based on the analysis of the physical properties of granite residual soils,microbial solidification tests are conducted on granite residual soils with different infusions times using a mixture of Bacillus pasteurii and urea colloidal solution.And Experiments are conducted by using Solidified samples of different treatment conditions for the unconfined compression strength(UCS)test,calcium carbonate precipitation test and disintegration test.In this paper,X-ray diffraction(XRD)and scanning electron microscopy(SEM)are also used to analyze the microstructure besides.Based on the above tests,the effect of cement concentration and treatment times on the microbial solidification characteristics of granite residual soil are investigated.The main research contents and achievements of this paper are as follows:(1)Microbial induced calcium carbonate precipitation technology(MICP)solidification test was carried out on granite residual soil based on Bacillus pasteurii.The test proved that microbial solidification could effectively improve the unconfined compressive strength,calcium carbonate formation content and disintegration resistance of samples.(2)The concentration of cementing fluid has a significant effect on the reinforcement of granite residual soil.Under the same number of perfusion times,the reinforcement effect of cementing fluid with a concentration of 1.0M is better than that of 0.5M,1.5M and 2.0M,and the maximum strength of soil column sample reaches 85 7kPa.In addition,at the same concentration of cementing fluid,the more times of perfusion,the better curing effect of the sample;The unconfined compressive strength of samples has a good positive correlation with calcium carbonate production.(3)Through XRD analysis,the calcium carbonate crystal generated by microbial curing belongs to calcite;The calcite crystals produced by the soil samples treated with low concentrations(0.5mol/L,1.0mol/L)were smaller in size,and some crystal forms showed obvious clusters,which showed good curing effect.However,the calcite crystals generated by the soil samples treated with high concentration(1.5mol/L,2.0mol/L)cementation solution are larger in size,and the morphology of the crystals is mostly laminar massive.(4)The solidification effect of MICP technology on granite residual soil is between sand and silt.The microstructure of the solidified sample is different from that of microbial solidified sand,but the solidification process and mechanism are similar.Combined with microscopic analysis,the solidification mechanism of microbe-induced calcium carbonate precipitation(MICP)on granite residual soil can be obtained.