| The use of microbial grouting to reinforce soil has operability,economy and good environmental protection characteristics,and can be used for road soft foundation treatment,side slope reinforcement and other projects,and has good development prospects.In view of the granite residual soil that is common in the slope engineering,the microbial grouting reinforcement laboratory test was carried out,and the typical slope in the project was selected to carry out the stability study of the microbial grouting reinforced slope.The following work was mainly carried out:First,the indoor grouting test of denitrifying microorganisms to strengthen the disabled granite soil is to determine the calcium carbonate content,strength test,and permeability test of the samples before and after grouting,and comprehensively evaluate the solidification effect of the denitrifying microorganism MCP on the disabled granite soil.The MICP of denitrifying microorganisms has a good effect on sand solidification.After the grouting test,the strength index,permeability parameters and plasticity of the soil are all improved.The cementing liquid with a calcium ion concentration of 0.25 mol·L-1and a ratio of 1:2:2 has the best solidification effect on sand.The unconfined compressive strength of the sand sample after treatment is increased by 39.2%and the direct shear strength Increased by 53.71%,permeability coefficient decreased by 1 order of magnitude.In a cement with the same calcium ion concentration,increasing the nitrogen source concentration can effectively increase the strength parameters;in a cement with the same nitrogen source concentration,increasing the calcium ion concentration can effectively increase the strength parameters without significant impact on the permeability of the sample.Secondly,the data obtained from the grouting test is parameterized,combined with the calculation of finite element analysis software,and four reinforcement schemes are compared and analyzed:face protection,face protection+fixed feet,face protection+strong waist,face protection+strong waist+solid The influence of the foot on the safety factor of slope stability,the calculation and analysis of the microbial grouting to strengthen the slope to improve the slope stability,provide a theoretical basis for the design of soil slope protection engineering.Microbial grouting has a positive effect on soil reinforcement.The reinforcement scheme of numerical simulation also shows that the microbial grouting can improve the stability of the slope.Among the four slope reinforcement schemes,the reinforcement of the slope toe can effectively improve the stability of the slope.In consideration of other factors,it is recommended that the reinforcement scheme of protective surface+fixed foot is adopted in the actual project.Compared with the calculation results of the unreinforced slope,and compared with the plan of strengthening the slope surface and the slope toe,the plan of pile grouting inside the slope body is damaged,and it has no anti-sliding effect.In this simulation calculation,the use of microbial grouting technology to reinforce the side slope and reinforce the toe and slope surface is the most effective treatment plan.Finally,on the basis of existing simulations,considering the impact of rainfall infiltration,the Van Genuchten formula with higher accuracy is used to fit the characteristic parameters of the microbial grouting soil infiltration function,and for unsaturated soil slopes with different grouting depths The coupling analysis of the seepage field and stress field of rainfall infiltration is carried out.The calculated transient pore water pressure is used to calculate the slope safety factor considering the influence of matrix suction.Calculations show that the initial rainfall increases the moisture in the soil,and the permeability coefficient of the soil also increases,which makes the later rainfall infiltrate the slope more and induce landslides and other geological disasters.After the slope surface is strengthened by microorganisms,this trend is slowed down.With the increase of the thickness of the reinforced slope,under the same conditions of duration and rainfall intensity,the negative pore water pressure area is continuously reduced,which is beneficial to the edge. |
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