Study On The Improvement Of Silt By Microbial Mixing Into Silt Induced Calcite Precipitation

In recent years,geotechnical engineering problems related to microbial activities have received more and more attention.As a new environmentally friendly,green and sustainable soil improvement technology,microbial induced calcium carbonate precipitation(MICP)has broad application prospects in the field of geotechnical engineering.The existing research on soil reinforcement by microorganism is mainly aimed at sandy soil with large particle size,and the research on silt is less.The reinforcement method is mainly grouting reinforcement.Compared with sand,the pore throat of silt is small,which will affect the injection of microorganisms,leading to difficulties in grouting and uneven reinforcement effect.Compared with the grouting method,the mixing method is to mix microorganisms into the soil to induce calcium carbonate deposition reinforcement,which requires less mechanical labor.Taking marine silt as the research object,this paper discusses the effect of microbial mixing into silt to induce calcium carbonate deposition to reinforce soil.The main conclusions of this paper listed as follows:(1)The feasibility of microbial mixing silt to induce calcium carbonate deposition reinforcement.The samples were prepared by mixing the bacterial solution into silt,and then the surface infiltration provided the cementing solution of calcium source and urea.By comparing the silt treated with different cement concentration and infiltration wheel number,it is found that the water stability of silt can be improved by increasing the cement concentration and infiltration wheel number,and the stable polyhedron calcite morphology is easier to form on the microstructure.(2)Sealing time after mixing bacterial liquid with silt.By controlling the sealing time of bacterial liquid,the influence of the sealing time of bacterial liquid on the reinforcement effect of the sample is explored.The results showed that the optimal sealing time was 12 h.With the increase of infiltration cycles,the effect of sealing time on the urease activity of bacterial liquid in soil samples gradually decreased,and the first round of infiltration had a greater impact on the sample.(3)Influence of infiltration wheel number on reinforcement effect.The influence of the number of infiltration rounds on the reinforcement effect was studied through multiple rounds of infiltration of cement,and the samples with different saturations of bacterial liquid mixed with silt were selected for comparison.The results show that the water stability of the cemented liquid mixed with microbial infiltration is better,and the water stability of the sample is significantly improved after 4 rounds of infiltration.The total calcium carbonate production and unconfined compressive strength of the sample increase with the increase of infiltration rounds,and the higher the number of infiltration rounds is,the more obvious the improvement effect is.(4)Study on direct mixing of microorganism and silt.The cementing material will no longer cement the soil through infiltration,and it is attempted to mix the cementing material with bacterial liquid and silt directly to explore the feasibility of making it have a certain strength.The results show that good reinforcement effect can be achieved under the condition of simplifying the curing process.