Abstract.

This study involves the influence on slope stability of notches located at the toe of rock and soil slopes. A notch could be open or closed. An open notch is a cut made at the toe of a slope as a result of wave action. A closed notch is a discontinuity at the toe of a slope resulting from the stress release taking place when a cut with a sloping face is made in a layer of rock. Open and closed notches can propagate as a result of gravity induced stresses inside the slopes. Using the principles of Linear Elastic Fracture Mechanics theory, it was determined that that the notch act as stress concentrator. Since the gravity induced stresses are the higher at the tip of a notch, the failure of the slope will start at the tip of the notch. The angle of propagation, α, of the secondary cracks emanating from the tip of an open or closed notch can be obtained from the following relationship: sinα + (τ/ σn)(3 cos α − 1) = 0. In this equation, τ is the gravity shear stress parallel to the longitudinal axis of the notch, and σn is the gravity stress normal to the axis of the notch. The measured and calculated value of α using this equation compared very well for both open and closed notches developed by slopes in the field and laboratory.

1. Introduction

Investigations were carried out to study the mechanics of notch formation in soil and coastal slopes forming part of the shorelines of England and the United States. The influence of the notch (a wave induced cut in the soil or rock) on the stability of these slopes was also analyzed. The selected soil coastal slope are located at Aldbrough on the north east coast of England and Vicksburg, Mississippi in the U.S [1, 2, 3]. The selected rock coastal slope is located in Dover, on the coast of England. Also, a laboratory soil slope with a toe crack was tested in the laboratory. Figures 1 through 4 shows the notches in the soil and rock slopes. The slope shown in Figure 1 is located in the Holderness coast in the north east part of England. The height of the slope is about 3 meters, and its inclination is about 65 degrees. The slope is made of the Holderness till [1, 2].

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