Multi-scale Experimental Study On Mitigating Erosion Of Slope By Microbial Technology Under Rainfall Conditions

In southern China,rainfall covers a wide range,lasts for a long time,and has a strong rainfall intensity.All kinds of slopes have been eroded by rain for a long time,which leads to slope erosion,soil erosion and even collapse and landslide.The existing slope protection methods have the disadvantages of excessive volume,high construction cost and high maintenance cost.In this paper,the microbially induced calcite precipitation technology is combined with slope anti-erosion protection.Firstly,a series of simulated rainfall tests was carried out on sand slope models treated by MICP,and the effect and influencing factors of MICP on erosion control of sandy soil slope are explored.Then,taking the soil collected in the field as materials,the slope model containing fine-grained soil was treated with MICP and simulated rainfall test,and the feasibility of MICP for controlling rainfall erosion of fine-grained soil slope was explored.Finally,MICP and simulated rainfall tests were carried out on the site slope under field conditions,which provided a new idea for the engineering application and popularization of MICP.The main research results of this paper are as follows:1.The influence of MICP treatment on sandy soil slope depends on sand gradation.The slope erosion with C_u=4.7 and 9.7 is effectively alleviated,and the total soil loss is reduced by 64.8%and 84.4%respectively compared with untreated slope.However,the slope erosion with Cu=2 and 2.8 increased by 2%and 1.4%.2.The calcium carbonate shell tightly binds the sand particles together,at the same time reduces the permeability,transforms the internal seepage into surficial flow and increases the surficial flow;Seepage and surficial flow are two competitive mechanisms of rainfall erosion,and the mutual restraint of these two mechanisms mainly depends on sand gradation.3.In the slope containing fine-grained soil,the reinforcement effect of MICP is related to the content of fine-grained components,and the higher the content of fine-grained components,the worse the reinforcement effect.After MICP treatment,the erosion reduction of silt-gravel slope with more fine particles is only 23.62%,while that of collapsed soil can reach 96.51%.4.MICP technology can be effectively applied to the on-site slope,changing the erosion pattern of the on-site slope when it is eroded by rainfall,reducing the permeability of the slope,slowing down the speed of rainwater infiltration and the velocity of wetting front,and effectively improving the surface penetration resistance of the slope,which is linearly related to the calcium carbonate content of the slope.Generally speaking,a series of slope models in laboratory and on-site slopes have been treated by MICP,and artificial rainfall simulation tests have been carried out.This paper probes into the influencing factors of MICP in sandy soil slope,and verifies the feasibility of MICP method in the field of rainfall erosion resistance of slope containing fine soil,which has certain engineering practice value.It broadens the road for the application prospect of microbial reinforcement technology,and provides a new idea for the treatment of slope rainfall erosion.