Discussion On Treatment Of Heifangtai Loess Landslide By Using Radial Well

China is a serious disaster area for loess landslides.And landslide induced by irrigation is an important form of loess landslide.In view of such landslides,scholars put forward various measures to prevent and control it.Drainage is an important measure to prevent and control landslides induced by irrigation.Due to the vertical permeability coefficient of the loess is far greater than the horizontal permeability coefficient,the common drainage engineering such as the horizontal well or vertical well is difficult to achieve the desired results.This article takes Heitai which is located in Yongjing County of Gansu Province as the research object.On the basis of hydrogeological survey and indoor saturated permeability experiment,combined with the hydrology and meteorology data of Heitai area,we set up a three-dimensional hydrogeological numerical model to study the drainage effect of the radiation well project in the Heitai tableland area.By comparing the influence on the spring flow and groundwater level under different well pattern as pumping water,we select the best radiation well plan.The main conclusions are as follows:1.Through the investigation and data collection of spring spots in Heitai area,we find that the spring spots in loess layer are mainly concentrated in the southeastern region.It is basically consistent with the distribution of Loess Landslides.The ratio of spring flow in loess layers to spring flow in gravel bed is between 1:1.14 and 1:1.86.2.Through indoor saturated water penetration test,it is concluded that the horizontal saturated permeability coefficient of loess in Heitai area is between 0.25 m/d-0.6 m/d,and that the vertical saturated permeability coefficient is between 0.43 m/d-0.75 m/d.Generally speaking,the vertical permeability of loess is greater than that of horizontal permeability.3.Through the simulation of six factors that affect the drainage effect of the radiation well,such as the length of the tube,the number,the elevation angle,the depth of the shaft,the distance between the radiation well and the tableland and the spacing of the radiation well,the best layout scheme of radiation well is selected.The parameters of the optimal well layout method are: 5 radiant tubes are set up in the radiation well,the length of each radiant tube is 80 m,the elevation angle is 3 degrees,and it is fan-shaped to the tableland,the shaft depth is set at 3.15 m above the top of clay layer,the distance between radiation well and boundary is 260 m and the distance between two radiation wells is 300 m.According to the plan,31 radiating wells are set up along the edge of the plateau.After the simulation we found that this plan can get rid of the groundwater in the loess plateau,and reduce the groundwater level at the edge of the plateau,so as to achieve the effect of preventing and controlling the loess landslide.