An earth Slope or soil slope is an inclined surface of soil mass which can be either natural or man-made. Different types of slope failures and of their failure surfaces are discussed below.
Types of Slope Failures
Soil slope failures are generally of four types :
- Translational Failure
- Rotational Failure
- Wedge Failure
- Compound Failure
- Translation failure occurs in the case of infinite slopes and here the failure surface is parallel to the slope surface.
- A slope is said to be Infinite, when the slope has no definite boundaries and soil under the free surface contains the same properties up to identical depths along the slope.
- As said above, when the soil along the slope has similar properties up to a certain depth and soil below this layer is strong or hard stratum, the week topsoil will form a parallel slip surface when failed.
- This type of failure can be observed in slopes of layered materials or natural slope formations.
- In the case of rotational failure, the failure occurs by rotation along a slip surface and the shape thus obtained in slip surface is curved. Failed surface moves outwards and downwards.
- soils, the shape is circular while in case of non-homogeneous soils it is non-circular.
- Rotational failure may occur in three different ways :
- Face failure or slope failure
- Toe failure
- Base failure
- Face failure occurs when soil above the toe contains weak stratum. In this the failure plane intersects the slope above .
- Toe failure is the most common failure in which failure plane passes through of .
- Base failure occurs when there is a weak soil under the toe and failure plane passes through of .
- Rotational failure can be seen in finite slopes such as earthen dams, embankments, man-made slopes etc.
- Wedge failure, also known as block failure or plane failure, generates a failure plane that is inclined.
- This type of failure occurs when there are fissures, joints, or weak soil layers in slope, or when a slope is made of two different materials.
- It is more similar to translational failure but the difference is that translational failure only occurs in case of infinite slopes but wedge failure can occur in both infinite and finite slopes.
- A Compound failure is a of translational slide and rotational slide.
- In this case, the slip surface is curved at two ends like rotational slip surface and flat at central portion like in translational failure.
- The slip surface becomes flat whenever there is a hard soil layer at a considerable depth from .