What Is a Retaining Wall?
Retaining walls are rigid wall structures that support soil laterally help so that they can maintain the surface of the ground at different elevations on either side of the structure.
If there is no retaining wall support, the soil at a higher elevation would tend to move down till it acquires its natural, stable configuration.
Consequently, the soil that is now retained at a steeper slope than it can sustain by virtue of its shear strength exerts a force on the retaining wall. There are various types of retaining walls constructed to keep soil in a safer state as discussed below.
Retaining Wall Types
Following are the types of retaining walls,
1. Gravity Retaining Wall
Gravity Retaining wall assures its stability by its own weight. These walls are majorly designed to eliminate the overturning effect of the lateral earth pressure and do not induce tensile stresses within the section.
Gravity retaining walls are suitable for low heights and are not economical for large heights. It can be made from stone, bricks, mass concrete, and precast concrete blocks.
Its section is of trapezoidal shape with a base width between 0.3 and 0.5 H, where H is the height of the wall and the top width is between 0.2m to 0.3m.
In the case of a concrete gravity retaining wall, a top width of 0.3 m is recommended for the proper placement of concrete.
2. Cantilever Retaining Wall
Reinforced concrete cantilever types of retaining walls are recommended for heights up to 7 m. This type of wall has a vertical stem monolithic with the base.
A slender section can be used in this retaining wall the tensile stresses within the stem and the base is resisted by steel reinforcement.
In case the slope of the wall is exposed a small backward batter of about 1 in 50 is provided in order to compensate for any forward tilting of the wall as shown in Figure.
3. Counterfort Retaining Wall
Counterfort retaining walls are used for heights more than 6m. Its stem provided acts as a slab spanning between the counterfort support. The distance between support is about 2/3 H but should not be less than 2.5 m.
4. Buttress Retaining Wall
A buttress wall is a form of counterfort wall. These types of retaining walls are built on the face of the wall and not within the backfill.
Buttress walls are not too popular because of their buttressed shape exposed outside which consumes space and spoils the appearance.
5. Crib Retaining Wall
The crib wall is shown in the figure. Crib walls consist of a series of boxes made from timber, precast concrete, or steel members, which are filled with granular soils. It acts as a gravity wall with the advantage of a quick erection.
Crib walls can withstand large displacements of soil due to their flexible nature. It is usually fitted so that its face has a batter of 1 in 6.
The width of the wall varies from 0.5 to 1.0 H and is suitable for walls up to a height of about 7.0 m. Note that the crib wall should not be subjected to surcharge loadings.
6. Gabion Retaining Wall
These retaining walls are constructed from rectangular metal cages or baskets. A gabion wall is made from a square grid of steel fabric, generally, 5 mm in diameter and spaced 75 mm apart.
The gabion baskets are usually 2 m long and 1 m in cross-section. Each basket is provided with a center diaphragm divided into two equal 1 m 1 m sections which add stability.
At the time of making stone-filled baskets are secured together with steel wire of 2.5 mm diameter. The base width of the gabion wall is about 0.5H.
A typical wall is shown in the figure. A good-looking face can be provided by slightly stepping back each succeeding layer.
7. Sheet Pile Retaining Wall
Sheet pile retaining walls are constructed from a series of interlocking piles individually driven into the foundation soil.
Nowadays, modern sheet piles are constructed from steel, timber, or precast concrete sections are also used.
Sometimes, a Cantilever sheet pile wall is held in the ground by the active and passive pressures that act on its lower part.
8. Anchored Earth Retaining Wall
These types of retaining walls are fixed at the base and are supported by a row or two rows of ties or struts placed near the top.
9. Diaphragm Retaining Wall
Diaphragm walls can be reinforced concrete walls or sheet pile walls. It includes a vertical concrete reinforced concrete slab fixed in position.
Wall is held in position by the passive and active pressures acting on its lower portion.
10. Reinforced Earth Retaining Wall
In this retaining wall, the use of reinforcement to strengthen the soil has been known for centuries. In the past straws are used to strengthen unburnt bricks and fascine mattresses have been used to strengthen soft soil deposits prior to road construction.
The main phenomenon working in reinforced earth walls is that a mass of soil can be given tensile strength in a specific direction if the lengths of a material capable of carrying tension are embedded within it in the required direction. Reinforced earth has been used in many geotechnical applications.
Here, we are only concerned with retaining structures. A reinforced earth wall is a gravity structure.
In conclusion, understanding the tensile strength of concrete through tests like the split cylinder test is vital for ensuring the structural integrity and longevity of concrete elements. By considering the tensile behavior of concrete, engineers can make informed decisions during the design, construction, and maintenance of various infrastructure projects, ultimately contributing to the safety and reliability of our built environment.
What is a retaining wall?
A retaining wall is a structure designed to hold back soil or other materials to prevent erosion or slope failure. It is commonly used in landscaping and civil engineering projects to create level terraces, prevent soil movement, and enhance structural stability.
What are the different types of retaining walls?
Gravity Retaining Walls: These walls rely on their weight and mass to resist the pressure exerted by the retained soil. b. Cantilever Retaining Walls: These walls use a reinforced concrete slab or stem that is anchored to a footing to provide stability. c. Sheet Pile Retaining Walls: These walls are made of interlocking steel, vinyl, or wood sheets that are driven into the ground to retain soil. d. Anchored Retaining Walls: These walls are reinforced with cables or tendons that are anchored into the ground to counteract the soil pressure. e. Gabion Retaining Walls: These walls consist of wire mesh baskets filled with rocks or other suitable materials to create a stable retaining structure.
What are the pros of gravity retaining walls?
Simple design and construction.
Cost-effective compared to other types of retaining walls.
Provide excellent stability for low to moderate soil pressure conditions.
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