岩溶地区不同利用方式土壤土力学特性垂直变化特征

以黔中岩溶地区不同利用方式的土壤为研究对象，采用野外调查和室内试验相结合的方法，研究了土壤黏聚力c、内摩擦角φ及紧实度随不同土壤利用方式、不同土层深度的变化特征。结果表明:土壤黏聚力c总体随土层深度不断增大，在0-35 cm内受不同土壤利用方式的影响比较明显；土壤内摩擦角φ在0-50 cm土层内，呈“S”形变化，受母质影响显著，三种不同土壤利用方式总体变化趋势基本一致；林地、灌草地、坡耕地土壤在垂直剖面上都存在着上松下紧的状况，在0-20 cm内，坡耕地土壤紧实度均小于林地和灌草地，20 cm以下坡耕地和灌草地土壤紧实度基本一致，但均大于林地，三者均保持着不断增大的趋势。研究表明:植被生长对于改善土壤力学性能具有一定的影响。因而通过加强植被保护与管理和调整坡耕地利用方式是改善土壤力学性能，防治土壤侵蚀和控制石漠化的主要手段。 

Vertical distribution of soil mechanical properties under different land use types in karst area

Soil erosion refers to a process that soil and soil parent materials are destroyed under the exogenic action. To understand impacts of land use type on soil mechanical properties and to provide scientific basis for soil erosion，the characteristic of distribution of soil mechanical properties at various soil depths (0-50 cm) under three land use types(woodland，shrub-grassland，slope cultivated land) at typical limestone site in Huaxi district in Guiyang city is researched by means of fields vegetation investigation，soil compaction and shear tests in this study. Guiyang city is located in east the slope of the Yunnan-Guizhou Plateau with well developed karst landform，and the soil types there are mainly yellow soil with sticky heavy- texture. In this study，slope cultivated land are bare slope land without crops，vegetation of shrub-grass land is dominated by Pyracantha fortuneana and ferns，vegetation woodland is dominated by Pinus massoniana. 30 sample plots are selected totally in the study including 10 plots of slope cultivated land，10 plots of shrub-grassland and 10 plots of woodland. Soil samples from 0-50 cm in depths with 10 cm for a layer that totaling in 5 layers are collected. It turns out that soil cohesion c increases along with depth，which significantly affected by land use types at 0-35 cm deep. The change of soil internal friction angle φ isn’t apparently different at 0-50 cm deep under different land use types and shows S-shaped on the whole，indicating that soil internal friction angle φ is affected by parent material. Soil compaction increases along with depth in different land use types，the soil compaction of the woodland and shrub-grassland are higher than slope cultivated land at 0-20 cm deep. The soil compaction，increasing with depth，in the shrub-grassland and the slope cultivated land has the same tend below 20 cm deep，which is higher than that in the woodland. Research shows the growth of vegetation can improve soil cohesion c and soil compaction. Therefore，protecting and recovering vegetation in karst area and changing land use of slope cultivated land are the main approaches to protect soil and control rocky desertification.