Study On Soil Disintegration In The Retreat Zone Of Lancang River Huangdeng Power Station

Huangdeng Hydropower Station on Lancang River is located in the core area of the three parallel rivers.This area has a fragile and sensitive ecology,frequent geological disasters,narrow ecological environment zone and poor stability.A large amount of hydropower development has led to aggravated soil erosion,ecological environment deterioration,and prominent contradiction between energy development and ecological environmental protection.Soil disintegration is an important index to measure soil corrosion resistance.The study on disintegration characteristics of typical soil and root-bearing soil in the water-level zone of Huangdeng Hydropower Station on Lancang River provides a basis for soil erosion prevention and control and sediment reduction in this area,and also provides a choice for vegetation restoration in this area.In this paper,the disintegrability and physical and chemical properties of five typical soils were measured by field sampling and laboratory test,and the correlation between soil disintegrability and soil properties was analyzed.Secondly,field disintegration tests were carried out in this area to determine the disintegration amount,disintegration rate and root characteristics of five suitable herbaceous root-soil complexes of differentω₀ plants in the water-level zone,such as Cynodon dactylon（Linn.）Pers.,Canna indica L.,Cyperus alternifolius L.,Arundo donax var.versicolor and Acorus calamus L.,and to analyze the effects of initial water content on the disintegration of root-bearing soil in the water-level zone.The results are as follows:（1）The disintegration of the tested soil was shown in order from strong to weak:red soil,yellow brown soil,silted soil（top）,silted soil（bottom）,purple soil.Purple soil of differentω0 did not completely disintegrate within 90 minutes,red soil completely disintegrated,and the underlying silted soil wasω₀<12%,it can be completely disintegrated,and the upper silt and yellow brown soil.It disintegrates completely at18%.（2）Soil disintegration is closely related to soil fluid plastic limit,mechanical composition,porosity and other properties;The linear equation of soil disintegration rate and total nitrogen,silt and liquid limit of the five soils atω₀ saturation has a high fitting degree.The soil disintegration property can be predicted by soil total nitrogen content,silt content and liquid limit.（3）When ω₀ is low,herbaceous roots can reduce the amount and rate of soil disintegration;whenω₀ is high,roots can increase the amount and rate of soil disintegration and promote soil disintegration.Among the five root-containing soils,Cynodon dactylon（Linn.）Pers.showed the strongest disintegration resistance,while Canna indica L.showed the weakest.（4）In the unsaturated state,the root system with d≤1mm showed obvious anti-disintegration effect,the root system with d>2mm promoted disintegration;In the saturated state,the root characteristics of d≤1mm had no significant relationship with the disintegration amount and disintegration rate,while the roots of d>1mm had the effect of promoting disintegration.Conclusion:For ω₀ saturated red soil,yellow brown soil,silted soil and purple soil,soil total nitrogen content,silt content and liquid limit can be used to predict soil disintegration;Whenω₀ was lower,herb roots could inhibit soil disintegration,whenω₀ was higher,roots could promote soil disintegration;In the process of soil erosion control and ecological environment restoration in Huangdeng hydropower Station reservoir area,necessary forest and grass or engineering measures should be taken to comprehensively control the red soil and yellow brown soil around the reservoir.On the premise of strengthening the protection of purple soil,make agriculture better,make forest better;Fine root plants should be preferred in the vegetation restoration of the water-level zone formed after the completion of the power station reservoir under the premise of suitability.