Study On The Application Of Plastic Blind Pipe In The Drainage Of Farmland Concealed Pipe

As a new type of composite geotechnical drainage material,plastic blind pipe has many advantages,such as high surface opening rate,good water collection,large porosity and strong compressive resistance.It has been widely used in underground drainage and drainage engineering of civil and water conservancy projects,especially in underground drainage projects of farmland.However,the effect of seepage drainage in the application and construction of plastic blind pipes is not clear,so it is urgent to conduct a systematic and comprehensive analysis and Study on the seepage characteristics and precipitation effect of plastic blind pipes.Based on the above background,this paper measured the permeability coefficients of blind pipes with three common specifications and three different combinations of outer filter materials,summarized their changing rules,designed the drainage combination scheme of plastic blind pipes with different burial depth,spacing and layout,and simulated their drainage capacity.The research results have positive significance for the selection criteria and development and application of plastic blind pipes in agricultural and water conservancy projects.By combining the permeability coefficient test of plastic blind pipe with the numerical simulation of seepage flow,the following work is carried out and the conclusion is drawn:(1)In terms of the outer filter material,the outer filter material of the plastic blind pipe is determined by the aquifer permeability coefficient,which has the most obvious influence on the permeability coefficient of the plastic blind pipe system,and directly determines the approximate range of the permeability coefficient of the plastic blind pipe system.As for the porosity of blind pipe,when the porosity of blind pipe is between 65%and 90%,the porosity and the permeability coefficient of blind pipe are positively correlated,but with the increase of porosity,the permeability coefficient increases slightly.As for the diameter of blind pipe,the influence of the change of the diameter of blind pipe on the permeability coefficient of blind pipe is almost zero,while the diameter of blind pipe is positively correlated with the permeability of blind pipe.However,when the diameter of blind pipe exceeds 194 mm,the clogging phenomenon is slightly worse than that when the diameter of blind pipe exceeds 150 mm.(2)Three-dimensional seepage simulation of drainage capacity of plastic blind pipes with different burial depth,spacing and layout was carried out.The middle point of the two ditches is the highest point of groundwater level,the closer to drainage ditches or vertical blind pipes,the more significant the control of groundwater level is,the closer the groundwater level is to the depth of blind pipes;the farther away from the agricultural ditches or vertical blind pipes,the weaker the control effect is.Increasing the buried depth of underground pipes can increase the cumulative groundwater drainage when the recovery period is reached and improve the drainage effect;smaller distance between underground pipes is conducive to surface soil drainage,the smaller distance between underground pipes,the faster the decline of groundwater level,also means the higher drainage efficiency.Compared with increasing the buried depth of blind pipes and reducing the distance between blind pipes,the cumulative drainage in the initial 4 days can be increased.