Keeping hold (Retaining) the Wall (Sustainability)

Types: Here we are going to discuss few common types of wall sustainability. Some types are given as follows: 

• The first type is called "Gravity Retaining Wall". In this type, the weight of the wall decides its stability. In this type, we usually use plain concrete or masonry, also called stone work. Though this type is not recommended for large heights wall as its not economical.
•  The second type is called "Semi-Gravity Retaining Wall". In this type, a little amount of reinforcement is given near the back face to reduce the size of the section of a gravity retaining wall. It is also called "Semi-Gravity Wall".
• The third type is known as "Cantilever Retaining Wall". This kind of wall is constructed of reinforced cement concrete. It'll have a thin stem and a base slab cast. It is considered very economical up to a height between 6 to 8 meters.
• The fourth type is "Counter-Fort Retaining Wall". These walls consist of thin vertical slabs, called as Counter-Fort. These slabs are spaced across the vertical steam at a regular gap. These slabs bind the vertical stem with the base slab. Therefore both the slabs (vertical and base) span between Counter-Forts. The idea behind providing Counter-Fort is to minimize the total force and bending moments in both the slabs (vertical and base). These walls are considered economical for a height of more than 8 meters.

Design: The foremost work before the designing is to evaluate the soil. Soil should be checked on two parameters:

• Influence of the earth pressure
• Bearing capacity of the soil

To understand the above two parameters, the following evaluation must be performed:

• Unit weight
• Angle of sheer resistance
• Cohesion intercept
• Angle of wall friction

Once the pressure of earth is determined, the next step is to check the stability against sliding, overturning, bearing capacity failure and tension.

Modes of Failure: There are three common types of failures as given below:

• Sliding
• Overturning
• Bearing failure

But apart from these three, the following mentioned two modes must be considered if the underneath soil is weak.

• Shallow Shear Failure: It may happen along the cylindrical passing through the heel of the retaining wall. It occurs because the extra force stresses along the cylindrical surface within the soil mass. But, it has been noticed generally that safety against horizontal sliding is factored out the shallow shear failure. Therefore, the factor against sliding must should be greater about 1.5 to protect shear failure to occur. 
• Deep Shear Failure: It happens mostly along the cylindrical surface in case of a weak layer of underneath soil. In such case the critical failure surface is measured by trial and error functions.