Characteristics Of Soil Pressure Distribution Behind Soil Bunds On Purple Sloping Farmland

In the Three Gorges Reservoir area, the purple soil slope cultivated land is mainly cultivated land resources, accounting for 78% of the area of farmland. It shows that the development utilization and protection of purple soil slope cultivated land is an important issues relating to food security and ecological safety of the reservoir area. “Terrance” is regulation and lower-yield fields in important ways of the three gorges reservoir area farmland, However, with natural factors(slope, soil saturated and unsaturated working conditions, soil moisture, etc.) in the construction, development and utilization of the bund human unreasonableuse etc, cause the study area bund collapse, water damage and other extremely serious. Bunds collapse is the essence of the soil of lateral soil pressure over bund candy can withstand the pressure of soil by the limit equilibrium state, eventually leading bunds collapse. Practice has proved that to solve the problem bundscollapsed fundamentally, the need for comprehensive treatment. Governance and development through the introduction of a combination of roads, this is an effective way to combat bunds collapse.In this paper, the soil in situ monitoring methods, self-made means of laboratory simulation model box and the Field combination field monitoring, as the research object is the behind soil pressure of bunds of purple soil slope cultivated land. On the distribution characteristics of bunds behind soil pressure were analyzed. First vertical distribution characteristics under different soil pressure behind the bunds of high mode of study; Then use the M-K mutation analysis method to identify point mutations in purple soil slope farmland soil pressure distribution behind the bunds of high along the wall of the study area; Finally the effects of different factors to soil pressure distribution such as soil moisture(saturated and unsaturated conditions working conditions, moisture content), and the slope of the bund. The main conclusions are as follows:(1) Vertical distribution in the different types of soil pressure behind the bunds high of showing a certain regularity. Soil pressure along the bunds high with the increase of soil depth distribution is nonlinear, specificly, soil pressure increases with the height of the first soil depth in the upper soil layers with bunds, When a soil depth of about 1/3 ~1/4 high of the bunds, as to achieve the maximum of soil pressure, after soil pressure in turn, decrease with the increase of soil depth, soil pressure behind of bund distribution presented as "small, large" hyperbolic shape. From the perspective of the scope of test monitoring, Vertical distribution characteristics soil pressure behind of bund can be described with a specific quadratic equation.(2) The use of Mann-Kendall method of field monitoring 60 cm high, 70 cm, 80 cm and 140 cm candy been pressure value for mutation analysis, The results show that four kinds of bunds of soil pressure behind the mutation will occur within ±1.96 confidence interval with distribution of soil depth, specific point mutations by highly different bund high varies. Specifically, the between of 10~15 cm high in 60 cm high of bund, the point mutation in the wall; 70 cm high, mutation point between 10 to 15 cm; 80 cm high, mutation point between 10~20 cm; 140 cm high, mutation point between 30 to 50 cm.(3) In a saturated soil condition to unsaturated condition, After the bund the soil pressure over the performance of each soil moisture infiltration time varies. The obvious lag of soil pressure in behind of bund with soil water infiltration change, the longer and deeper the lag with time, after the soil pressure of the bund of soil over time, rendering the law of diminishing.(4) The soil under the condition of different moisture content, soil pressure of the bund with different soil moisture content varies. Specifically, With the decline in the soil moisture content that soil pressure of behind bunds have been reduced. When the moisture content of the larger fluctuations, changes in the value of bunds of soil pressure behind the greater, And with increasing depth of soil, soil pressure behind the threshold value gradually converge.(5) Slope has a significant impact on the soil pressure bund behind each soil. Overall, 20°slope under soil pressure behind the threshold value is greater than the slope of 15°; Gradient between 15°and 20°bund behind each soil layer,soil pressure value in soil 10 cm, 50 cm, 70 cm have significant changes, 20 cm, 30 cm, 40 cm, 60 cm difference is not significant(p<0.05).