Experimental Study On Microbial Solidification And Corrosion Resistance Of Loess

Loess is widely distributed in China.Due to its characteristics of microporosity,joint development and unsaturated,serious soil erosion and landslide often occur in the hilly region of loess under rainfall conditions.In order to improve the erosion resistance of loess,Microbially Induced Calcite Precipitation（MICP）technique was used in this paper to conduct an experimental study on microbial solidification of loess.The law of propagation of Sporosarcina pasteurii was analyzed,the microstructure and composition of microbe solidified loess were studied,the mechanism of microbe solidified loess was revealed,the method of microbe solidified loess was established,and the anti-erosion performance of microbe solidified loess was tested and analyzed under the condition of artificial simulated rainfall.The main conclusions of this paper are as follows:（1）The MICP technology can effectively solidify the loess surface,improve the strength of loess and reduce the permeability coefficient.Compared with the original loess,the permeability coefficient of the samples cured by microorganism for four times is reduced by more than 90%.（2）When the concentration of the cementing solution（CaCl₂ and CO（NH₂）₂ mixed solution）is greater than 0.4mol/L,the CaCO₃ content generated in the pre-mixing and curing samples increases first and then decreases,and reaches the peak value when the depth of the soil layer is about 5mm.Compared with the un-premixed solidified samples,the CaCO₃ produced is more evenly distributed.The CaCO₃ generated in the un-premixed solidified samples is mainly concentrated in the surface soil and decreases significantly with the increase of depth.（3）For the non-premixed solidified loess sample,the content of calcium carbonate in the soil layer within 5mm depth increases with the increase of the concentration of solidified cementing solution.However,when the soil depth was more than 10mm,the CaCO₃ content of the solidified samples with a concentration of 1.2mol/L was the highest,and the CaCO₃ production of the solidified samples with a concentration greater than this solution decreased.Therefore,it is more economical and effective to choose the concentration of 1.2mol/L cement solution to solidify loess.（4）After curing,the density of soil increases and decreases with depth.The maximum density of the surface soil reaches 1.96g/cm³,increasing by 45.49%.The density of the premixed samples is more uniform than that of the un-premixed solidified samples.（5）Through XRD analysis,it can be seen that the crystal type of CaCO₃ generated after curing treatment is calcite,among which,the crystals generated in the premixed and un-premixed curing samples are rhombic hexahedral,with grain diameters of 10-20μm and 4-8μm,respectively.According to the observation of optical microscope,the CaCO₃ crystal generated plays a filling and cementing role between soil particles,which improves the density and strength of the microbe solidified loess and reduces the permeability.（6）Using MICP technology to solidify loess can effectively improve the erosion resistance of loess.The more times of curing,the smaller the erosion modulus,the larger the runoff modulus,and more than 7 times of curing,both tend to be stable.The loess slope cured for more than 7 times can resist continuous scouring for more than 1h when the rain intensity is 120mm/h.