| A large number of rock mass engineering,such as slope,dam foundation,tunnel and so on,are destroyed along the weak structural plane such as rock joints and fissured,while the traditional rock mass reinforcement technology,such as cement grouting,chemical grouting,has the problem of great disturbance to the environment and not environmental protection.MICP,as a new non-toxic and pollution-free interdisciplinary technology,has become a research hotspot in recent years.At present,MICP is mainly used in sand solidification,and a large number of research results have been obtained.Based on the previous research,this paper tries to apply the microbial grouting to the reinforcement of fractured rock mass.In this paper,the urea-producing microorganisms were firstly extracted from the soil.In order to improve the urease activity of the microorganisms,orthogonal tests were carried out on the self-extracting bacteria and bacillus pasteuris to obtain the optimal microbial culture conditions.At the same time,to provide a test to further reinforce fractured rock mass,the sand column curing trials of different chemical additives to seepage of the reinforced sand column and nuclear magnetic resonance?NMR?test,to evaluate the efficacy of the microbial curing under different solution,get the best ratio of chemical additives and reinforcing process,and sand column Karman-Kozeny seepage model is established.Finally,on the basis of the above tests,the experiment of microbial grouting and reinforcement in fractured rock mass is carried out,and the following conclusions are mainly obtained:1)Extracted from the soil microbes and pap bacillus 3 times of purification for a quick high purity of bacterial colonies,dyeing optical microscope showed that production for gram positive bacteria,mainly by the cell wall peptidoglycan and acidic polysaccharides,including teichoic acid because of teichoic acids negatively charged,so the negatively charged cell surface as a whole,and the form of a single,all are rods,high purity.2)According to the orthogonal test,the optimal culture conditions for self-extracting urea-producing bacteria are:urea content 20g/L,inoculation quantity 1.0ml,rotation speed 180r/min,culture time 72h.Bacillus pasteuris were:urea content 40g/L,inoculation quantity 2.0ml,rotation speed 180r/min,culture time 72h.3)The permeability coefficient of microbial solidified sand samples decreased from the order of 10-2cm/s to the order of 10-4?10-5cm/s.SEM scanning results and NMR results showed that adding 0.1mol/L NH4Cl solution+0.1mol/LNa HCO3 solution could change the morphology of calcium carbonate precipitation crystals,which were irregular cube polygons and had certain adsorbability,increasing the adhesion of calcium carbonate precipitation in sand samples and improving the uneven reinforcement of sand samples.Based on the solidification coefficient f of the microbial sand column,the karman-kozeny seepage model of the microbial sand column was established to quantify the relationship between the precipitation of calcium carbonate and the reduction of the permeability coefficient of the sand column.4)After the fissure rock sample is strengthened by microorganisms,the fissure is bonded and filled by calcium carbonate precipitation,and cemented as a whole.The permeability coefficient decreases from an order of magnitude of 10-2cm/s?10-3cm/s to an order of magnitude of 10-5 cm/s?10-6cm/s,which meets the engineering impermeability requirements.After self-extracting urease producing bacteria grouting to reinforce the single fissure sandstone sample,the cohesive force increased by 85.10%,the internal friction Angle increased by 48.09%,the shear strength increased by more than 90.00%,and the shear force-shear displacement characteristic curve changed significantly.Under the high normal stress,it is the chewing mode of climbing slope.5)Based on microbial solidification coefficient f,the karman-kozeny seepage model of microbial solidified fractured limestone was established.The relative error between the test permeability coefficient and the calculated permeability coefficient was2.60%?4.94%.It shows that the model can truly reflect the seepage flow of microbe-solidified fractured sandstone backfill.Considering the quantitative relationship between the torsional factor?and the microbe-solidified torsional coefficient Ts',the model of the peak shear strength of microbe-solidified fractured sandstone was established,which better reflects the functional relationship between the peak shear strength and the fracture backfill. |
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