Experimental Study On Soil Structure Improved By Biomaterial

With the increase of population and the rapid development of social economy,there are more and more areas of soil and water pollution in China,and the problem of soil degradation is becoming more and more serious.At present,the main problems of soil degradation are: soil compaction and hardening,acidification,salinization,erosion,loss of organic matter and chemical pollution,etc.,which have seriously hindered the production of land.As one of the solutions to soil remediation problems,soil amendments are widely used in various engineering applications.The principle of soil amendments is to improve soil productivity by improving soil properties,structure and fertility.Today,most research is on the soil improvement effect of traditional soil amendments(biochar,straw ash,etc.).Therefore,in this paper,a comparative experiment was used to apply a new type of biomaterial soil conditioner to the improvement of laterite soil in Nanchang,Jiangxi,to study its improvement effect on the structure of Nanchang laterite,and to analyze the distribution characteristics of soil pores after improvement according to BJH theory..The research work and conclusions are as follows:(1)The Nanchang laterite(<5mm particles)was dry sieved,and the results showed that the aggregates of laterite in Nanchang were mainly composed of 5-3mm and 2-1mm particles,accounting for 30.19% and 34.8%,respectively.The proportions of 3-2mm,1-0.5mm and <0.5mm aggregates were 15%,11% and 9.01%,respectively.After three treatments of fast wetting(FW),slow wetting(SW)and pre-wetting disturbance(WS),the content of aggregates >2 mm was ranked as WS > SW > FW,indicating that soil resistance to FW disturbance was the worst.(2)A new type of biological material modifier was used to improve the lateritic soil in Nanchang area.The experiments compared the effects of six modifier ratios(10%,5%,2%,1%,0.8%,0.5%)on laterite,and the results showed that the ratios of1%、0.8% and 0.5% were relatively better.The effect of different water addition amounts(15ml,12.5ml,10 ml,7.5ml,5ml)on soil improvement was studied.The results showed that different mixing methods of biomaterial conditioner and soil would affect the formation of large particles of soil aggregates.Adding 10 ml of water can More and larger soil particles are formed in the soil,and the soil stability is also higher.(3)Four different ratios(0.2%,0.4%,0.6%,0.8%)of modifiers were used to improve the laterite soil.The results showed that aggregate particles >5mm appeared in the soil after the improvement of the four proportions of amendments,and the contents were 21.2%,28.9%,21.4% and 25.4%,respectively.Among them,0.8% of the amendments had the best improvement effect,with a proportion of >3mm The soil aggregate particles accounted for the highest proportion,at 69.9%;the average weight diameter(MWD)of the soil after the improvement of the four proportions of amendments increased by 38.1%-61.4%,and the geometric mean diameter(GMD)increased by 57.7%-92.3%.After the improved soil was treated by FW,SW,and WS,the order of aggregates >2mm was still WS>SW>FW,indicating that soil amendments had the same effect on the three disturbances.(4)The isotherm adsorption and desorption curves of soil before and after improvement were measured by nitrogen adsorption method.The results show that there are a certain number of large pores in the soil,and there are many blind pores in the small pores.The number of macropores and the total pore content in the soil also increased with the increase of the amendment ratio.The pore size and pore volume map and the pore size and cumulative specific surface area map of soil were calculated according to the BJH theory.The results show that the micropore distribution of the modified laterite is still dominated by <25nm pores,and <10nm pores account for the most.The contribution of pores <10 nm to the pore volume and specific surface area gradually increased with the increase of the amendment ratio,indicating that the biomaterial amendment could increase the number of micropores in the soil.(5)Electron microscope scanning detection of soil before and after improvement showed that the surface morphology of soil aggregates was complex,and the difference was mainly reflected in the size and shape of soil surface binding particles.With the increase of the proportion of the modifier,the particles bound on the surface of the soil aggregates became larger and more numerous,and the content of iron and aluminum elements continued to rise,indicating that the biological material modifier can increase the content of iron and aluminum oxides in the soil,so that the small particles are bound in the soil.Together they form larger soil aggregates and improve the stability of the aggregates.