| China is one of the countries with the most serious loess soil erosion in the world,especially the loess plateau in the middle and upper reaches of the Yellow River.The scope,intensity and harm of soil erosion are handful in the world.With the increase of human engineering activities and the aggravation of extreme severe weather,soil erosion becomes more and more serious.The core of soil erosion prevention and control work is to improve the anti-erosion ability of soil,and the anti-erosion ability of soil is closely related to the soil’s water stability and physical and mechanical behaviour(hydro-mechanical behavior),therefore,it is of great significance to carry out research on the hydro-mechanical properties of loess for soil and water conservation and ecological environment protection in China.In this paper,MICP was proposed as the technical support for the breakthrough.By carrying out laboratory tests such as slaking test,penetration test,and scour test,macro test was combined with microstructure analysis,the hydro-mechanical behavior of MICP modified loess,such as water stability,penetration resistance and scour resistance,as well as the influence rules of key factors,were systematically expounded.From the perspective of soil texture and soil structure,the anti-erosion mechanism of MICP modified loess was revealed.On the basis of the relevant experimental research,this paper also establishes the relevant infiltration-water flow-erosion model,which makes a certain breakthrough in the theory of water-mechanics.The main work and research results are as follows:(1)MICP treatment has a significant effect on the hydro-mechanical behavior of loess,and surface spraying MICP treatment process is effective for improving the erosion resistance of loess.(2)The water stability of MICP-treated loess was studied by slaking test,the slaking rate and cumulative slaking rate of the sample after immersion were significantly reduced compared with those before MICP treatment,among which the slaking rate and cumulative slaking rate both decreased by more than 50%.(3)The structural strength of MICP-treated loess was studied by micro-penetration test,the surface penetration strength of the sample after multiple rounds of modification can reach 159.24 k Pa,which is about 50 times that of the sample before treatment.(4)A series of hydraulic erosion tests were carried out on MICP-treated loess under simulated rainfall conditions,the formation of a stable calcium carbonate on the surface of the loess treated by MICP can significantly reduce the soil-runoff phenomenon,a theoretical model of infiltration-water flow-erosion was established.(5)Cementation rounds,cementation solution concentration and sand content all had certain effects on the effect of the hydro-mechanical behavior of the MICP treated loess.Specifically,the cementation rounds was positively correlated with the content of calcium carbonate,the cementation solution concentration affected the size of calcium carbonate crystal,and the sand content affected the permeability coefficient and structural characteristics of the sample.Within the research scope of this paper,7rounds of MICP cementation were performed with 1.0 M cementing solution,which was the optimal process parameter.(6)The improvement of the anti-erosion ability of MICP treated loess is the formation of a solid calcium carbonate crust on the soil surface from calcium carbonate generated by MICP,which effectively inhibits the erosion damage of slope caused by precipitation.Below the crust,the cementation of calcium carbonate promotes the aggregation of soil particles.When the sand content is high,when the sand content exceeds 30%,the combined action of sand particles-calcium carbonate-soil particles forms a more stable structure.These strengthened micro-structures and weakened the water-immersed slaking of the loess and enhance the structural strength. |
