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

MICP is a new technique for soil reinforcement by microorganism.Microorganism induced calcium carbonate precipitation technology is an important research topic in this century.The technology has the characteristics of environmental protection and simple operation.Currently,the research object of MICP technology is mainly large-grained sand,and the grouting method is mainly adopted.If the grouting method is used to reinforce silt,the reinforcement effect is not ideal.Compared with the grouting method,the mixing method can strengthen silt better,and different calcium sources have different effects on microbial solidified silt.The types of calcium carbonate crystals produced by MICP tests with different calcium sources and the failure modes of samples are different.In order to better study the performance of MICP technology solidified silt,three calcium sources,calcium chloride,calcium acetate and calcium sulfate,were selected to explore the influence of calcium source types on microbial solidified silt.A series of unconfined compressive strength test SEM test and calcium carbonate content test were carried out to analyze the change of calcium salt concentration of different calcium sources.The influence of different infiltration interval time and different infiltration wheel number on mechanical properties of silt the main conclusions of this paper are as follows:（1）The influence of different calcium sources on the reinforcement effect.When using different calcium sources（analytical pure calcium acetate and industrial pure calcium chloride and industrial pure calcium sulfate）,the industrial pure calcium chloride sample is superior to other calcium salts in all aspects,and the calcium chloride sample is superior to the calcium acetate sample in all aspects.SEM microscopic analysis results show that the precipitation product induced by microorganisms is calcium carbonate.Crystal types of different calcium sources are different,and the crystal of calcium chloride sample is most s Tab..（2）The influence of infiltration interval time on reinforcement effect.The influence of infiltration interval time on microbe induced calcium carbonate was investigated by changing the infiltration interval time.The results showed that the interval time of infiltration was optimal at24h.Through the exudate of conductivity measurement,24h capacity urea enzyme hydrolysis of urea is best,this is associated with bacteria,with the increase of infiltration time interval,the microbes can have enough time to urea hydrolysis catalyst,when high urease activity of urea hydrolysis faster,thus more quickly to the formation of calcium carbonate,unconfined compressive strength of the sample also increases.（3）The influence of the number of infiltration rounds on the reinforcement effect.The influence of the number of infiltration rounds on microbial-induced calcium carbonate was studied by changing the way of the cementing solution with multiple rounds of infiltration.The results showed that Ca CO₃ generation and unconfined compressive strength of the sample increased with the increase of the number of infiltration rounds,and the strength of the sample increased significantly when the number of infiltration rounds increased to 3 or 4 rounds.With the increase of the number of infiltration rounds,the uniformity of the sample is significantly improved.