Investigation On Earth-rock Fill Dams Seepage And Slope Stability Considering The Effect Of Unsaturated Soils

The instability of soil slope due to seepage flow is a subject of considerable interest in the field of soil mechanics and geotechnical engineering. The major difference of the engineering properties between saturated soils and unsaturated soils is derived from matric suction. But at present, the effect of seepage flow in unsaturated soils is often ignored in slope stability analysis, such as earth dams, masonry dams and dikes.As saturated soils, Darcy's Law has been shown to be valid for the water flow through unsaturated soils. In this case, based on the mass conservation of solid and liquid phases, a governing equation for 2D saturated-unsaturated seepage problems is derived with the fundamental unknown of the pressure head. The general limit equilibrium methods are discussed in this thesis. The formulation of the Ordinary and simplified Bishop's methods in the safety factor computation is derived under the consideration of seepage. In the slope stability analysis of unsaturated soils, the effect of matric suction contributed to the shear strength is considered.Some classical dams are analyzed to ensure the location of phreatic surface, equipotential lines, contours, total flux, and gradients of seepage by SEEP/W, such as dams with clay core, or homogenous. And based on mathematical model of saturated soils, the seepage analysis of these classical dams subjected to steady seepage is conducted. At the same case, the comparison of the results calculated by three different kinds of method, like as the mathematical model of seepage flow in saturated-unsaturated and saturated soils, electric model test. In addition, the transient seepage analysis in one dam subjected to the rapid drawdown of the reservoir water level is conducted using the model of saturated-unsaturated seepage. Taking these three kinds of dams as the examples, the stability analysis is finally illustratedby SEEP/W and SLOPE/W. The results present the effectiveness of the combination of seepage flow and stability analysis.