| In order to fully master the effect of applying pipe drainage technology to control saline-alkali water logging of cultivated land and improve farmland water environment for many years,the project area of Wuduizi pipe drainage in Pingluo of Ningxia was taken as the research object.The varietyof groundwater depth,soil moisture content,soil total salt content and groundwater salinity was explored and analyzed at the area through field monitoring and laboratory tests in this thesis.According to the regional characteristics and basic situation of Yinbei irrigation district,the related calculation program is written in various calculation methods of pipe spacing,and their applicability are analyzed with C programe,and the calculation method suitable for the pipe spacing is proposed in Yinbei irrigation district of Ningxia.The optimization model of buried depth and spacing of farmland pipe drainage with the minimum cost per unit area as the objective function is established through the study of different constraint conditions of suction pipe spacing,.According to the results of soil texture analysis in Yinbei irrigation district of Ningxia and field testing results of optimum selection of wraped materials outside drainage pipe in agricultural comprehensive development project.The relationship between the drainage flow and the action head?the design of the drainage rate and the variation of the drainage flow with time-variation law were analyzed systematically when different geotextiles were used for the suction pipe of the Yinbei irrigation district.The main conclusions as follows:(1)The results of field monitoring show that.the control effect of pipe drainage on groundwater depth is obvious.it can effectively reduce the groundwater level.The total salt content of soil is greatly reduced after arrangement of pipe drainage,some regions are generally below 1g/kg.Performing linear regression analysis of monitored groundwater salinity and soil total salt content data by DPS software,the linear regression equation is y=1.5228x+1.011,of which R2 is 0.7765,p is 2.36289E-7,the absolute error is between-1.29 and 0.49,the results show that there is a dominant positive correlation between the salinity of groundwater and the total salt content of soil.(2)According to the theoretical calculation formula of the distance between the pipe drainage in literature,the C language program is compiled,and the distance is calculated,analyzed and discussed under various working conditions.Taking the design of wuduizi pipe drainage project in Ningxia as an example,the result of programming shows that:Under the condition of stable flow,it is suggested that both Aviriyanov-Quxingye formula and the Hooghoudt formula should be calculated at the same time.Under unstable flow conditions,it is recommended to use Quxingye formula or semi-empirical formula calculated by 1.31 for the design and calculation of pipe spacing in Yinbei irrigation district.(3)Non-woven fabric+sand filter material has the best effect under the condition of permission,Considering the mechanical integration construction,68g/m2 non-woven fabric have obvious linear relationship between water head and drainage discharge,and the discharge is also larger than the discharge corresponding to the designed drainage rate,which is there is still surplus,and the flow attenuation is also low,and it is not easy to be broken in the process of transportation and construction.Therefore,it has a better application prospect compared with other test materials.(4)According to the model,the minimum cost per mu is 455.2 yuan when the buried depth of the pipe drainage is 1.75 m and the distance is 77 m in the project area of the Wuduizi. |
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