Seepage And Flooded Characteristics Of Clay Layer Located In Downstream Of Right Auxiliary Dam Of Nieerji Hydropower Station

The downstream of the right auxiliary dam of Nierji project is Baitushan terrace, which consists of alluvial and pluvial deposit of Pleistocene. The upper is the low liquid limit or high liquid limit clay, and the lower is loaded sandy pebble or sandy pebble.During the investigation and assessment of the flooded condition of the downstream of the right auxiliary dam of Nierji project, the following two questions are researched in special, one is the seepage feature of clay layer, and the other is the criteria of the assessment.The object of the flooded research and assessment is the ground water in the superficial clay. The classical theory believes that the water level in clay is same to that in the aquifer when the aquifer was confined. Combining with the hydrological dynamics, the author points out that the water level in the clay should be lower that that in the confined aquifer owning to the head lose during the seepage in the clay with bound water. The above theory is verified during the investigation in the field.The criteria for flood should be depended on the site condition, and the traditional simplified and dogmatic model should be excluded. To decide the flooded criteria in crop area, secondary salinization phenomena should be investigated at first, and secondly the types of the crop should be confirmed. And then the corresponded critical buried depth of the ground water can be confirmed.To building area, the first important thing is to assess the influence of the resident environment. The safety of the existing buildings should be decided based on the loading of the building, the foundation type as well as the buried depth of the foundation. The strength reduction and the deformation incensement of supporting layer of the bases after saturated should be studied. The corresponded investigations and tests should be carried out when silt, soft soil, expansive soil and collapsed loess et al exist in the bases.Through the research in the area, the new recognition about the seepage in the clay is drawn. At last the theory is put into force in the flooded study of the area.