| The distribution area of loess in China is about 6.4×10~5 km~2,which accounts for 6.6%of the total land area,mainly distribute in the northwest and central of China.Since ancient times,the Loess distribution area has been the region with frequent human activities,but the fragile geological environment in the loess region has been threatening the safety of the lives and property of the residents near the loess slope.In recent years,with the development of the economy,the construction activities of railway engineering,tunnel engineering,water conservancy project and other construction activities near the loess slope are expanding,and the occurrence rate of the geological disasters on the loess slope is increasing.Therefore,strengthening the study of loess slope have urgent practical significance.Previous studies showed that the strength distribution in toe of the slope has an important impact on the stability of loess slope.In order to reasearch further the strength distribution and influencing factors in the toe of loess slope,first we carried out a detailed investigation of the loess slope.and obtained the slope failure situation in the study area..We have designed a penetration resistanceinstrument that can measure the strength of soil.Based on the results of field investigation,this instrument is used to test the penetration resistance of toe of slope in selected slope,At the same time,we tested the moisture content and soluble salt content at different heights and depths at the toe of the slope in laboratory.Test results and research work of this paper are as follows:(1)In the field investigation of loess slope in the study area,it is found that 41.6%of the loess slopes are destroyed.Moreover,in those damaged slopes,whose toe of the slope has been destroyed account for 44.3%.At the toe of loess slope,There are often rainfall water,groundwater and plant water storage.Under capillary action,the moisture at the bottom can move up to a certain height,form a visible irregular infiltration line.(2)In order to find out the strength distribution in toe of slope,a penetration resistance tester for slope was designed,and a series of test experiments were carried out toe of slope.The experimental results show that the penetration resistance test instrument can easily and effectively identify the stress distribution in the slope body,and the experimental results provide important reference for the analysis of the stability of the loess slope.(3)Due to the diffference of loess slope aspect,slope height,the strength distribution at toe of slope have different characteristics.But the rule is basically that the bottom soil is wet and soft,and the penetration resistance is small.With the increase of the height of toe of slope,the penetration resistance increases.The penetration resistance of the soil above 60 cm height is several times that of the bottom soil,and the trend is more obvious when the light in slope is stronger.(4)Due to the presence of capillary action,the water content of the toe of slope in the vertical shows a staircase distribution,that is,the lower the soil moisture content in the higher loess layer,the water content of the 80 cm height soil layer can reach to several times even dozens times as much as the water content of the soil layer of 0 cm.In the horizontal direction,the water content inside the slope is larger than the water content at the slope surface,and the higher from the slope bottom,there are greater difference value.In the deep of the slope,the difference of moisture content of the soil at different heights is getting smaller and smaller.(5)The penetration resistance and water content of soil have a close negative correlation,that is,The wetter the soil,the smaller the penetration resistance value is.According to the result of curve fitting,they are closest to power function relations.(6)At the toe of loess slope,the movement of water is relatively frequent on the surface and bottem of the slope,which leads to erosion at the toe of the slope. |
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