Numerical Simulation Of Soil-bund Stability On Purple Soil Sloping Farmland

Soil-bunds play a key role in controlling soil erosion on sloping farmlands due to its significant soil conservation effect.Because soil-bunds possess the merits of inexpensive,convenient construction,ecological suitability,and great erosion control effect,as important as stone-bunds,still have a larger proportion in the sloping farmland consolidation and high standards basic farmland construction projects in the Three Gorges Reservoir area.Ensure the soil-band stability is the key to protect the slope farmland.After the field investigation about existing soil-bund of structures,types and utilization,we stratified sampling soil on typical soil-bund to tests physical and mechanical properties by laser particle size analysis,direct shear and so on.Stress-deformation analysis method was adopted to simulation soil-bund stress and strain distribution,and limit equilibrium analysis was adopted to calculate stability coefficient under natural and saturated conditions,respectively.Then the response model of soil-bund stability coefficient to structure under natural conditions was constructed.The results are as follows:(1)The physical and mechanical properties of bund soil and bund back soil in purple soil sloping cropland without significant difference.Under the natural condition,the shear strength of upper part soil of bund is significantly greater than the middle and lower part.After bund soil water saturation,the shear strength decreased obviously.(2)Lower part of soil-bund possesses the largest total stress value,followed by middle and top part.When soil-bund height fixed,the maximum total stress value in middle and lower parts of soil-bund increase with outside slope increase,however,the trend in upper part is not obviously.In this case,the X-total stress in middle and upper parts of soil-bund decrease but the lower part increase.When soil-bund outside slope fixed,with the bund height increases,the values of maximum total stress and X-total stress showed a increasing trend.(3)For a given soil-bund height,the maximum value of X-displacement gradually mobile from the nearby soil-bund foundation to the above area with the outside slope increasing,this trend was relatively obvious when the soil-bund height is 1.4 m.For a given soil-bund outside slope,with the height increase,X-displacement did not occur significant redistribution,the maximum displacement area is relatively fixed.(4)Under the natural condition,both the height increase and outside slope steepen,the soil-bund stability coefficient is decreased,but the interaction effects of soil-bund height and outside slope is not significant.Under the saturation condition,the soil-bund stability coefficient was significantly reduced,and "short-slow" bund stability coefficient decreased more significantly.(5)The potential sliding surface of soil-bund are linear and circular arc,saturation has no obvious effect on the potential sliding surface morphology.