| Microbially induced calcium carbonate precipitation(MICP)technology is a new type of geotechnical solidification technology.This biomineralization reaction is widely present in nature.It has a wide range of application prospects due to its ease of use,fast precipitation rate,environmental applicability,and good tolerance.However,with respect to the current microbial reinforcement of geotechnical bodies there are problems such as uneven reinforcement effect and low generation rate of calcium carbonate in the cementing solution,resulting in limited curing strength,which is not conducive to the use of large areas.To this end,this paper takes a metal tailing sand in Hunan Province as the research object,uses a combination of theoretical analysis and experimental means,introduces electroosmosis on the basis of ordinary microbial grouting reinforcement,and carries out experimental research on the curing effect of graded electroosmosis on microbial reinforced tailing sand under the action of electroosmosis.The main research results of this paper are summarized as follows:(1)By electro-osmosis test on pure tailing sand,the optimum potential gradient and electro-osmosis time when electro-osmosis is applied to the tailing sand are obtained.Cumulative drainage,potential and current changes from inside the tailing sand,comprehensive analysis of the internal conductive mechanism and electro-osmosis principle of tailing sand.It is found that the electroosmotic effect of tail sand is the best at 1.25 V/cm.(2)By activation and cultivation of Bacillus pasteurii,under normal culture conditions(30~oC,150r/min),the growth trend of bacteria with urease activity was obtained.Late period of bacteria is not obvious,the activity reaches its maximum at 4-24h for logarithmic growth.Specific live bacteria count measured using coated plates,and the p H value around the bacterial solution reached a favorable growth environment after about 4h of incubation.(3)Take the normal culture of Bacillus pasteurii after 24h and put it into the homemade culture jar with electricity,and it was found that the weak electric field could effectively promote the biological activity of Bacillus pasteurii.The accelerated metabolism of bacteria raises the environmental p H and elevates the bacterial count,providing more nucleation sites for the induction of calcium carbonate precipitation.The macroscopic surface structure and microscopic morphology of calcium carbonate precipitation are different under different potential gradients,and the combination of calcium carbonate crystals under 0.5 V/cm gradient is good and the cementation effect is the best.(4)Microbial slurry reinforcement of tailing sand using graded electroosmosis and electrode conversion with different potential gradients set at the time of injection of bacterial and cementing liquids.Electroosmosis can effectively drive the migration of anions and cations,and the shear strength and calcium carbonate content of the specimens were measured in different areas after reinforcement,and it was found that the cohesive force of the sand samples after microbial reinforcement under the effect of electroosmosis increased by 37.3%compared with the sand samples after ordinary microbial reinforcement,and increased by 64.8%compared with the original sand samples,and the internal friction angle also increased accordingly.The highest strength of the internal grout opening area of the electro-osmotic monolithic sand sample,and the enhancement of reinforcement uniformity is obvious from the amount of calcium carbonate generation. |
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