Study On The Seepage Characteristics Of Double-river In Sponge City

The double-layer channel is a new type of channel.the upper open channel creats a hydrophilic space,and the lower is a waste drainage box culvert.Based on the study of the general working characteristics and design mechanism of double-layer channel,The physical characteristics and permeability of the two-layer channel soil and rock mixture are carried out.Based on the double river channel in Ba nan Chongqing china,This paper,Combining with laboratory test indicators,established the numerical model of double-layer river channel by FLAC 3D,analyzed the seepage field characteristics of double-layer channel.The main conclusions are as follows:(1)By reviewing the literature and the existing double-layer channel engineering,the functions,characteristics and applicable conditions of double-layer channel were summarized.The high backfill of the double-layer channel can also be used as a conservation body of the water,which can be used to make up the gap and utilizable strore water resources.(2)Based on laboratory test index and related literatures,Fredlund was selected for soil-water characteristics curve,and VG was adopted for the permeability coefficient function.Used SPAW software to analyze soil-water characteristics curve and the permeability coefficient function,and fitted analysis.(3)The main seepage direction of the double-layer channel is in direction of vertical channel flow.When double river channel is without geomembrane,there was a positive correlation between Seepage flow,maximum positive pressure value,maximum negative pressure value,lower culvert drainage hole displacement.and depth of the water.The bigger the water depth is,the upper infiltrates surfaced and spill point is.When double river channel is with geomembrane,there was no correlation between these factors.(4)when there is drain hole on lower culvert,seepage discharge increase.More closer the drain is,the bigger hydraulic grade is,the litter pore water pressure is.because drain hole can make the pore water pressure has dissipated vanishing.(5)When double river channel is without geomembrane,The maximum hydraulic gradient and the maximum negative pore water pressure increased,positive pore water pressure decreases effectively,the infiltration surface is obviously reduced,and the underground water level and the lower culvert side wall are lined with water holes.(6)The water depth increases in the upper open channel,and its seepage flow,maximum flow velocity and maximum positive pore water pressure decrease first and then remain unchanged.The maximum negative pore water pressure remains unchanged;The most powerful slope decreases.The water depth in the upper open channel increases,and its seepage flow,maximum flow velocity and maximum positive pore water pressure increase first,then remain unchanged.The maximum negative pore water pressure remains unchanged;For the unseeded double-layer channel of the upper open channel,the maximum slope drop is reduced,and the maximum slope drop remains the same for the double-layer channel with impermeability of the upper open channel.(7)when the water level of the upper open channel is changed,the seepage flow,the maximum positive pore water pressure and the maximum negative pore water pressure are calculated at the static water level of the water level variation range.The higher the velocity of the water level is,the more the seepage characteristic of the water level is similar to that of the initial water level.