Numerical Simulation Of Channel Seepage With High Groundwater

There are more complicated operation conditions in the irrigation area with high groundwater level.At present,the research on the lining of channel with high groundwater level is less,and it is crucial for the lining reconstruction and the sustainable development of high groundwater irrigation area to choose a lining,which can not only reduce leakage but also prevent the pressure.Based on the Yellow River Irrigation Area in Ningxia,this paper research on the effects of channel water level,groundwater level,the position of permeable solid lining,soil properties of channel foundation,and solid width on the channel leakage and lining optimization,which provides the optimal case for the reconstruction of the channel lining in the high groundwater level irrigation area like the Yellow River.The main conclusions of this paper are as follows:(1)When the groundwater level is shallow,the depth of channel and groundwater level has great influence on channel leakage.Due to the increase or decrease of the head difference,the leakage of the channel varies linearly with the depth of the channel water level and groundwater level.When the depth of groundwater level is deep,the depth of channel and groundwater level has little effect on the leakage of irrigation channel.(2)The location of permeable lining(through solid lining structure or lining slotting)has little influence on seepage in irrigation area with high water level.When the permeable lining is arranged at the bottom of the channel slope,the water-saving rate of lining in the irrigation period is the smallest and the maximum descending height of the infiltrate line in the non irrigation period is the largest.When the permeable lining is arranged in the middle of the channel bottom,the water-saving rate of the lining is the largest and maximum descending height of the infiltrate line is the smallest.The water-saving rate and maximum descending height of the infiltrate line are between the other two positions.when the permeable lining is arranged on the sides of the channel bottom.To some extent,the permeable lining impervious form can reduce leakage and the height of the infiltrate line.Considering comprehensively,in the channel section where groundwater level is higher than the bottom of channel,it can be considered that the the penetrating solids are arranged on both sides of the channel bottom.When the channel is full lining,the leakage rate of the channel is very small,and the water-saving rate of lining is very high.The full lining can be used when the ground-water level is lower than the channel bottom.(3)The permeability coefficient of channel foundation soil has great influence on channel leakage.In the permeable lining,the water-saving rate of lining under the channel foundation of gravel soil is the highest,the water-saving rate of lining under the channel foundation of sandy soil is low,the water-saving rate of lining soil under the channel foundation of sandy loam is the lowest.The maximum descending height of the infiltrate line under the gravel soil foundation is the largest,the maximum descending height of the infiltrate line in the sandy soil is lower,and the maximum descending height of the infiltrate line under the sandy loam foundation is smallest.The maximum descent height of the infiltration line increases with the increase of the soil permeability coefficient.When fully lining,the leakage of channels under different foundations is approximately equal,and the water-saving rate of lining is extremely high.(4)The width of permeable lining(through solid lining structure or lining slotting,etc.)has great influence on the leakage of channel.There is an inflection point for the leakage with the permeable lining width.According to the example of the Yellow River irrigation area in Ningxia,when the permeability coefficient of permeable solid lining is 2.00× 10-4m/s,the turning point is about 0.1m under the sandy loam soil foundation,and the turning point is about 0.25m under the sand soil foundation,and the inflection point under the gravel foundation is about 0.5m.The width of permeable solid lining has great influence on the leakage of gravel soil foundation,and has little influence on the leakage of sand foundation,and has fewer effect on the leakage of sand loam foundation.With the increase of permeability coefficient of channel foundation,The permeable solid lining has an increasingly significant effect on the seepage of channel.(5)The length of vertical baffle plate based on the optimization of lining seepage has great influence on seepage.The longer the length of deflector,the larger the actual seepage area,the less leakage of the channel,the higher the water-saving rate of the lining,and the smaller the elevation of the groundwater level.The arrangement of the deflector at the permeable area of the channel lining can reduce the leakage of the channel and the elevation of the groundwater level,and improve the utilization of water and the stability of the lining.