| Topsoil is the nutrient soil on which vegetation depends for survival.Power transmission and transformation projects span different landforms and landforms,so it is inevitable to disturb and destroy the surface in the construction process.The protection and utilization of topsoil resources is an important work of soil and water conservation and ecological restoration.This paper analyzes the deficiencies in the division of topsoil stripping index,the utilization measures of topsoil stripping and the improvement of topsoil in the power transmission and transformation engineering.Based on the soil organic carbon data set and the analysis data of the actual engineering topsoil nutrients,the nationwide stripping thickness index is delimited.Carried out an experimental study on vegetation restoration of topsoil layered peeling and mixed peeling and utilization measures,as well as an experimental study on the improvement and restoration of vegetation of topsoil on high and steep slopes by using polymer water retaining agent(SAP),and improved and summarized the construction technology of topsoil peeling,protection and utilization in power transmission and transformation projects.The research results are as follows:(1)According to the soil organic carbon data set,the soil nutrient classification map and topsoil stripping classification map of the country were drawn,and the peeling thickness index of topsoil was determined according to the way of topsoil utilization.In areas with organic matter content greater than 10 g/kg,the soil nutrient grade is 1-4,the peeling grade of topsoil is 1,and the peeling thickness is recommended to be 30-50 cm.In areas with organic matter content less than 10 g/kg,the soil nutrient grade is 5-6,the peeling grade of topsoil is 2,and the peeling thickness is recommended to be 20-30 cm.According to the nutrient characteristics of topsoil in each first-level district of national soil and water conservation zoning,the corresponding suggestions of topsoil stripping were put forward,which provided scientific and technical basis for the protection and utilization of topsoil in power transmission and transformation projects.(2)The vegetation restoration test results of stratified topsoil stripping and mixed topsoil stripping and utilization showed that,compared with mixed topsoil stripping and utilization,stratified topsoil stripping and utilization could effectively protect the nutrients and vegetation resources of topsoil and achieve better vegetation restoration effect.After one year of topsoil stripping and utilization,the vegetation coverage under stratified topsoil stripping was 22.97 %,8.94 % higher than the original vegetation coverage,while that under mixed topsoil stripping was 15.55 %,only 1.52 % higher than the original vegetation coverage.At the same time,the study also found that the longer the topsoil storage time,the more soil nutrient loss,the lower the biological activity,the worse the effect of topsoil restoration vegetation,it is suggested that the stripped topsoil should be restored within 3 months.(3)In view of the characteristics of low rainfall infiltration,low water content of topsoil and poor vegetation restoration effect on the high steep slope,the topsoil was improved by adding water-retaining agent to restore vegetation.The experimental study showed that on the slope of 45°～75°,adding 1.0 ‰(ratio of water-retaining agent to dry weight of topsoil)to the topsoil could effectively improve the vegetation coverage.It is suggested that water retaining agent should be added to improve the surface soil of high and steep slope in power transmission and transformation project.(4)On the basis of the existing technical specifications,combined with the results of this study,the content of topsoil stripping investigation is prepared,the process of determining the thickness of topsoil stripping is clarified,and the calculation method and construction technical requirements of the related technical parameters of topsoil stripping,protection and utilization are put forward. |
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