Effect Of MICP On Tailing Reinforcement With Ureaae Inhibitor NBPT

In order to solve the problems of grouting port easy blockage and uneven distribution of calcium carbonate in the current microbial grouting reinforcement technology,this study took a metal ore tailings as the experimental object,introduced urease inhibitor NBPT in the microbial grouting reinforcement process,and analyzed the effect of inhibitor concentration on Bacillus pasteurii.According to the inhibition effect of NBPT,the reasonable dosage of inhibitor NBPT was determined.At the same time,combined with the stress-strain relationship of solidified tailing samples determined by the triaxial consolidation undrained(CU)test,the optimization effect of urease inhibitor NBPT on the reinforcement effect of microbial grouting was compared and analyzed.The main conclusions are as follows:The Bacillus pasteurii solution experiment showed that the growth curve of the bacillus pasteurii was in line with Gompertz-Richards model,there was no obvious lag period,the bacillus pasteurii was an excellent strain.Bacterial urease activity was positively correlated with the OD₆₀₀value of Bacillus pasteurii,and increased with the increase of OD₆₀₀ value.Urease inhibitor NBPT extended the delay period of Bacillus pasteurii to a great extent,and the inhibition effect became stronger with the increase of NBPT content.0.1%NBPT could effectively prolong the 8h delay period,and less than 0.1%NBPT could inhibit the growth of Bacillus pasteurii,but did not prolong the delay period significantly.Through the analysis of the influence of the ratio of bacterial liquid to cementation liquid and the dosage of inhibitors on the production of calcium carbonate in the solution environment,it is found that the best ratio of bacterial liquid to cementation liquid is 1:3.With the increase of the dosage of NBPT,the production of calcium carbonate decreased gradually.When the dosage of NBPT was 0.1%,the formation rate of calcium carbonate was 87%.When the dosage of urease inhibitor was 1%,the formation rate of calcium carbonate was 77%.Grouting tests of microorganism reinforced tailings with different inhibitor doses show that the mechanical properties of microorganism cured tailings samples can be improved to a certain extent when the NBPT content is 0.1%and 0.25%.Among them,0.1%NBPT content improved the MICP reinforcement effect the most.Therefore,the use of 0.1%inhibitor NBPT content as additive can reduce the uneven distribution of Ca CO₃ and improve the effect of microbial grouting reinforcement.