On the Slope Stability of a Sea Dike with a Gentle Grade

The stability of downslope

Abstract

The slope stability of a sea dike with a gentle grade was studied in this research. The seepage water through the dike researches at the surface of the downstream slope and exudes on the surface.
Firstly, it was supposed that the stability of soil grains on the slope is dependent on the gradient of the slope, hydraulic gradient in the dike and others.
Then, as a part of the study of slope stability, the state of a thin sheet flow on the surface of downstream slope was theoretically discussed, being suggested by solving the energy eguation concerning thin sheet flow. The equation of non-uniform flow is as follows : dh/dx=sini-2αq (x) ∫^x₀q (x) dx/gh²-3ν∫^x₀q (x) dx/gh³/cosi-α {∫^x₀q (x) dx} ²/gh³=F₁ (h, x) /F₂ (h, x)
Then, it was explained that this equation may be solved by the method of iso-inclination or numerical calculation.
Secondly, assuming that the seepage water through soil grains exudes on the surface of downstream slope and flows together with the ohter exude water, it was supposed that the tractive power of thin sheet flow had influence on the stability of soil grains.
Thereby, the equilibrium expression on the stability was obtained as follows : a₁·tanψ+a₂·tan (θ-ψ) +a₃·I_f·h/D {cosθ+sinθ·tanψ} =a₁·tanψ_s
Some coefficients were determined by sand model experiments so as to put this theoretical expression to practical use.