Research On The Collapsing Gully Soil Permeability And The Improvement Experiment

Collapsing gully is the most serious soil erosion type in south China,Soil and water loss leads to ecological deterioration in hilly areas and it's a serious obstacle to develop mountain production and to promote the economy.The governance of collapsing gully is the key and difficult point of soil and water conservation in low hilly area of south China,however it has or long cycle,or large investment and other shortcomings to use of plant measures,engineering measures or comprehensive measures to governance collapsing gully.In recent years,chemical measures have got good results in controlling soil and water loss.In addition,chemical measures have many advantages,such as quick effective and low cost so it received wide public concern.W-OH is a kind of modified hydrophilic polyurethane composite material with high safety,which has been explored widely in desertification control,vegetation restoration,ecological slope protection and other aspects.At present,there are few studies on W-OH to impact on the collapsing gully.Therefore it has important practical value and guiding significance for the study to use W-OH impact on the collapsing gully.This study research on a collapsing gully in Tongcheng county of Hubei province,W-OH and plant fabres were explored in improving soil permeability,The basic soil physico-chemical analysis were carried out to see the material basis and internal causes of collapsing gully;Through the soil moisture characteristic curves to learn the distribution of soil porosity and the classification of soil water in each soil layer and by comparing with the curves to analyze the relationships and differences between undisturbed soil and remolded soil;A series of disintegration experiments were carried out to explore the disintegration characteristics of each soil layer,compared with the disintegration characteristics of undisturbed soil and remolded soil and obtained the effects of the amount of soil disintegration under different concentrations of W-OH;Used the uniform design method to design the ratio of different W-OH concentration and plant fibres consumption,carried out permeability improvement experiment on each soil layer,to explore the influence and extent of different experiment conditions act on permeability different soil layers,So as to select the optimal experimental conditions.The main conclusions are as follows:(1)The variation regularity of bulk density is sandy soil layer>red soil layer>clastic layer>surface soil layer,the natural moisture content is red soil layer>sandy soil layer>surface soil layer>clastic layer.The difference of free iron oxide content is red soil layer>surface soil layer>sandy soil layer>clastic layer.The clay content in mechanical composition of four soil layers is red soil layer>surface soil layer>sandy soil layer>clastic layer,and the sand content is clastic layer>sandy soil layer>surface soil layer>red soil layer,the soil organic matter content variation regularity is decrease basipetally of collapsing gully wall,surface soil layer has 18.48%and the clastic layer has 5.49%,The soil pH value is increase basipetally,it was acidic soil in general.(2)The soil moisture characteristic curves of the undisturbed soil in each soil layer of collapsing gully showed that at the stage of 0-100 kpa,the volume water content of each soil layer decreases rapidly,at the 100 kpa-500 kpa stage,the volume water content of the clastic layer decreased the most obviously,In general,the water binding capacity of surface soil layer and red soil layer is better than sandy soil layer and clastic soil layer;There is a big difference of proportion of porosity types between each soil layer,the aeration porosity:surface soil layer>clastic layer>sand layer>red soil layer;ineffective porosity:surface soil layer>red soil layer>sand layer>clastic layer.Compared with the soil moisture characteristic curves of remolded soil and undisturbed soil,the trend of volume water content decreasing with the increase of soil water suction is the same,but the amplitude variation is not as obvious as undisturbed soil.(3)The cumulative disintegration modulus(Bt)of the undisturbed clastic layer is the largest to 0.48 of the undisturbed soil,both the surface soil layer and red soil layer are the lowest to 0.03,the sand is 0.28;Clastic layer has the fastest disintegration rate,reached17.26cm~3/min,sandy layer takes the second place,reached 7.1 cm~3/min.The soil disintegration rate(B)of surface soil layer and red soil layer are both lower.Compared with undisturbed soil,the Bt of each soil layer of remolded soil have decreased to different extent,meanwhile,the variation of B over time also decreases correspondingly,but the overall variation regular is basically consistent with the undisturbed soil.Under different W-OH concentrations.(4)The permeability coefficient of different soil layers under different experimental conditions has been changed.According to the soil characteristics of each soil layer,the optimal improvement plan is corresponding given for different soil layers,the surface soil layer:W-OH concentration is 2%,the fiber length is 30mm;the red soil layer:W-OH concentration is 2%,the amount of W-OH is 0.3ml/cm~2;the sand layer:W-OH concentration is 2.5%,the amount of W-OH is 0.3ml/cm~2;the clastic layer:W-OH concentration is 2.5%,the amount of W-OH is 0.3ml/cm~2,the other experimental conditions are taken in the middle value.(5)In this study,the W-OH and degradable jute fiber are combined to act on the collapsing gully wall.according to the soil characteristics of each soil layer,the optimal permeability improvement plan is proposed,in order to increase the stability of collapsing gully wall and to achieve the aim of reducing water and soil loss.