Test: Finite Slopes - Civil Engineering (CE) MCQ

The two basic types of failure of a finite slope may occur: (i) slope failure (ii) base failure.

Stability analysis of Finite Slope:
(i) If the slope is of finite extend bounded by top and bottom surfaces, then it is termed as finite slope.
(ii) Failure of finite slope takes places due to rotation and failure plane is either circular or spiral.
(iii) Finite slope may have any of the following mode of shear failure.

• Slope failure
• Base failure

Slope failure:

• Face Failure: Failure surface passes through slope above the toe. This type of failure takes places in case of steep slope, soil mass near the toe is rigid or stringer in comparison to soil mass above the toe.
• Toe Failure: It is the most common mode of failure of finite slope in which failure surface passes through the toe. This failure also occur in steel slope when soil mass is homogenous above and below the toe.

Base Failure: 

• Failure surface passes below the toe.
• This type of failure takes place when soil mass below the toe is soft and weak in comparison to soil mass above the toe.

If the failure occurs along a sliding that intersects the slopes at or above its toe, the slide is known as slope failure.

The ratio of the total depth (H + D) to depth H is called the depth factor Df.

Planar failure surface may commonly occur in a soil deposit or embankment with a specific plane of weakness.

According to Bennet (1951), non-circular or composite slip surface may arise in homogeneous dam have foundation of infinite depth, rigid boundary planes of maximum and presence of stronger or weaker layer.

Failure of finite slopes occurs along a curved surface. In stability computation, the curve is represented by an arc of a circle or logarithmic scale.

The types of failure surface are: i) Planar failure surface ii) circular failure surface iii) Non-circular failure surface.

For toe failure, Df = 1; for base failure, Df > 1.

The stability of a finite slope can be investigated by the following methods:
(i) Culmann’s method of planar failure surface
(ii) The Swedish circle method
(iii) Friction circle method
(iv) Bishop’s method.