Optimization Design And Stability Analysis Of Meshed Ecological Drainage Ditch

The drainage ditch has the dual functions of drainage and water logging reduction.It is one of the necessary infrastructures for farmland and plays a very important role in agricultural production.Due to the depth of the drainage ditch in the farmland needs to meet the requirements of the standard of water logging reduction,and the impact of long-term water erosion and collapse,the soil channel in the farmland is generally 2.0～5.0m wide,and the channel accounts for about 3%of the cultivated land area.It is necessary to ensure the stability,permeability and ecology of the drainage ditch slope,and to effectively reduce the area occupied by the ditch.Seeking a new type of ecological drainage ditch structure will play a very important role in the construction of well-facilitated farmland in the future.On the basis of ensuring the basic function and ecology of the ditch,this paper optimizes the lining section structure of the farmland drainage ditch with the minimum width of the ditch mouth and the minimum amount of lining concrete,and proposes an excellent ecological lining scheme.The width of the ditch mouth can be controlled at about 1.0 m,and the ditch accounts for about 1.0%of the cultivated land area.The finite element analysis shows that the ditch has good stability.The main research contents and results are as follows:(1)On the basis of ensuring the drainage,water logging reduction,permeability and ecology of farmland drainage ditches,a new type of stepped meshing ecological drainage ditch structure is proposed with the minimum investment as the goal,and the ecological brick and ecological protection scheme is optimized.(2)Through theoretical analysis,the calculation formulas of anti-sliding,anti-overturning,base bearing capacity and brick shear and bending safety factor of channel slope under this lining method are given,which lays a foundation for stability analysis in practical application.A nonlinear optimization model is constructed.On the premise of channel stability and ecology,the minimum channel opening and the amount of brick concrete are taken as the objectives,and the engineering optimal size range of meshing brick is solved,which can provide the basis for practical engineering application.(3)Using the OptumG2 finite element analysis software,the numerical dynamic simulation is carried out with the meshing brick masonry scheme as the research object.The influence of the lining parameters such as the resistance between the upper and lower bricks,the width of the brick,the width of the base and the lateral displacement distance of the brick on the overall stability of the channel slope is compared and analyzed.The results show that:1)The influence of the base width on the slope stability is relatively small,which mainly plays the role of bearing bricks.2)With the increase of friction resistance between bricks and brick width,the overall stability of the slope gradually increases,but the improvement effect will gradually decrease.3)When the lateral displacement distance is equal to 1/3 brick width,the overall stability of the slope can reach the highest.With the increase of the lateral displacement distance of the brick,the bearing effect of the soil under the brick on the brick is more and more obvious.(4)Considering that the channel is often in the case of lateral seepage during normal operation,the slope safety factors of 16 working conditions under different water level combinations are simulated and calculated by using OptumG2 finite element analysis software for different soil conditions and various unfavorable factors.The results show that:1)Under the condition of seepage,the safety factor of the slope of the stepped meshing ecological brick masonry channel is still relatively high.2)During the construction period,because the side pier has not yet been poured,the stability of the channel slope will decrease when the groundwater level of the farmland is high or the water level difference is large.Therefore,the construction in the rainy season should be avoided as much as possible.After the completion,the integrity of the lining structure is improved,and the slope is difficult to lose stability.When controlling drainage,the influence of water storage in the ditch on slope stability is relatively small,which is of great significance for water saving in farmland and ecologicalization of drainage system.3)Under the condition of seepage,the vulnerable positions of the masonry slope are mainly the front and back toes of the basement and the bottom bricks.Therefore,in practical engineering,the stability of these positions can be enhanced by adding tooth ridges,slope piers,and integral pouring of the bottom bricks.(5)Through the analysis of engineering examples and the comparative analysis of various lining schemes,it is shown that the meshing ecological drainage ditch designed in this paper has good stability,and has many characteristics such as saving land,saving investment,good ecology,convenient construction and permeable.It has good practicability in the lining project of farmland drainage ditch.