Study On Strength Improvement Of Guiyang Red Clay By Microorganism By Different Immobilization Methods

As a kind of regional special soil,red clay is widely distributed in Guizhou Province.Its coverage area accounts for more than 70% of the total area of the province.The poor engineering properties of red clay make it difficult to be directly used in actual engineering construction.Can only be used after it has been reinforced and improved.Traditional red clay improvement methods mainly include lime stabilization treatment,fly ash stabilization treatment,lime mixing treatment,cement stabilization treatment,etc.These traditional red clay improvement methods,most of the improved materials are toxic materials,and in the production process It will produce a lot of greenhouse gases or harmful gases,it will also pollute the soil environment and groundwater resources,and cause great harm to our living environment.The microbial induced calcium carbonate precipitation technology(MICP technology)is a green and environmentally friendly soil improvement technology,which is widely used in expansive soil and sandy soil.In order to expand the application scope of this technology,this article takes Guiyang red clay as the research object and explores The effect of MICP technology on the reinforcement and improvement of red clay in Guiyang,and based on the properties of red clay,the innovative combination of immobilized microbial technology and MICP technology was carried out.By comparing the mechanics of reshaped red clay,microbial red clay and carrier microbial red clay The strength and the amount of calcium carbonate produced,and the improvement effect of this method is discussed.The main research contents are as follows:(1)Study on the cultivation of Bacillus basilus and the concentration of bacterial solution and urease activity A series of operating procedures for the activation,preservation and expansion of Bacillus basilicum were obtained.The culture was shaken in a constant temperature shaking box at 30°C and 160r/min for40-48 h,and the concentration of the bacterial solution and urease activity used in each test were controlled.The absorbance(OD)of the obtained bacterial solution is about 1.6 and the conductivity value is about 2.50ms/cm before it can be used to prepare the microbial red clay soil sample,and then the CU test can be carried out after curing in a thermostat at 30°C for 6 days.(2)Experimental study on carrier content.According to different immobilization methods,activated carbon and sodium alginate were selected as immobilization carriers,and the dosages of 4%,7%,10%,and 15% were set to explore the influence of different dosages of different carriers on the mechanical strength of reshaped red clay.Both activated carbon and sodium alginate affect the mechanical strength of red clay.The internal friction angle decreases with the increase of activated carbon,and the cohesive force is conversely.Sodium alginate increases the cohesive force of red clay,and the internal friction angle increases with alginic acid.The increase in sodium production decreases.(3)Study on the solidification effect of immobilized microorganisms on red clay.A triaxial CU shear test was performed on the microbial red clay,and the improvement effect was found to be unsatisfactory.Therefore,the combination of immobilized microbial technology and MICP technology was introduced to add an immobilized carrier to the microbial red clay,and then the carrier microbial red clay was added to the microbial red clay.The strength test shows that activated carbon has a synergistic effect on the red clay modified by MICP technology,while sodium alginate has a negative effect on the microbial red clay,and has a reduced effect.The activated carbon and sodium alginate form a composite carrier and when the amount of activated carbon is greater than In the case of sodium alginate,the coupling synergistic effect is very significant.(4)Research on the effect of microbial solidification by mixing the cement in advance for different times.The mixing time of the cementitious liquid before the bacterial liquid and the red clay will affect the mechanical strength of the microbial red clay to varying degrees.When the cementitious liquid is mixed with the red clay2 h in advance,the mechanical strength of the microbial red clay can be improved.(5)Research on solidification of red clay by bacteria and artificial extraction of urease.The mechanical strength of the artificially extracted urease solidified red clay is slightly higher than the mechanical strength after microbial solidification.The use of artificial extraction of urease can simplify the process of microbial cultivation,and it is easier to infiltrate the red clay,but it has low yield,high cost and complex technology.Compared with bacteria solidified soil,it is less economical than bacteria.It is not as suitable for practical engineering applications as bacteria.It also combines immobilized microbial technology.It can significantly improve the mechanical strength of the red clay solidified by microorganisms.During the reaction,the microorganisms are still metabolizing to produce new urease,and calcium carbonate precipitation can continue to form.(6)The determination of calcium carbonate content and its relationship with the carbon of shear strength index.Activated carbon is used as a carrier to immobilize microbial red clay,which can increase the amount of calcium carbonate precipitation and increase the cohesion of the red clay,but the internal friction angle does not increase;when sodium alginate immobilizes the microbial red clay,the amount of calcium carbonate precipitation decreases even No precipitation can be formed,and the cohesive force of the soil has increased,but the internal friction angle is reduced;when using composite carrier immobilization,with the increase of the amount of activated carbon,the amount of calcium carbonate in the soil increases significantly,and the cohesion The force and the angle of internal friction also increase,and the size of the angle of internal friction and cohesion is proportional to the amount of calcium carbonate produced.