A retaining wall is a structure that is designed to resist soil’s lateral pressure when the ground elevation changes beyond the angle of repose. Supporting soil laterally with retaining walls is a way to keep it at different levels. Retaining walls are structures that hold the soil down to a slope it is not designed to keep. They are used to hold soils at two different elevations, often in terrain with undesirable slopes or areas that require a more precise and controlled shaping of the landscape for purposes such as hillside farming or road overpasses.
Design considerations for retaining walls
Retaining walls can be either vertical or near-vertical structures that are designed to hold material on one side. They prevent it from slipping, collapsing, or preventing erosion. They are useful for supporting terrain where the soil’s angle is too high and would otherwise crumble into a more natural state. A retaining wall’s main characteristic is its ability to withstand pressure from the retained material, usually soil.
To properly design and install retaining walls, it is important to recognize the tendency of the retained materials to slide downhill due to gravity. This creates lateral pressure behind the wall. It depends on the angle and cohesive strength (c) and the direction, magnitude, and amount of movement that the retaining structure experiences.
The lateral earth pressures at the top of a wall are zero and increase proportionally to the lowest depth in homogenous soil. If not addressed properly, earth pressures can push or turn the wall. Hydrostatic pressure is also created by groundwater that has not been drained. For uniform height lengths, the total pressure or thrust can be assumed to operate at one-third of the lowest depth.
Proper drainage is essential behind walls to reduce pressure on the wall’s design. Drainage materials can reduce or eliminate hydrostatic pressure and increase the material’s stability behind the wall. Drystone retaining walls are usually self-draining. The International Building Code, for example, requires that retaining walls be designed to prevent overturning, sliding or excessive foundation pressure from water uplift. They also need to have a safety factor of 1.5 to avoid lateral sliding and overturning.
Construction of a retaining wall on site
Different types of retaining walls
There are many types of retaining walls. We’ll be discussing some of the most popular.
Gravity walls are built from stone, concrete, or another heavy material to resist pressure from the sides. They may also have a batter’s setback to increase stability and lean back towards the retained soil. They are usually made of mortarless stone, segment concrete units (masonry), or masonry units. Dry-stacked gravity walls can be erected without foundation and are flexible.
Reinforced Retaining wall
Reinforced concrete walls and reinforced masonry walls on spread foundations can be described as gravity structures. They are made of reinforcement bars and weight and provide stability against overturning. These are the most common types of walls:
Concrete Cantilever retaining walls
Cantilever retaining walls are made up of a wall that is attached to a foundation. Cantilevered walls can hold back significant amounts of soil, so they must be designed well. These are the most popular type of retaining walls. A slab foundation supports the Cantilevered wall. The slab foundation is also loaded with a backfill. Thus, the wall is stabilized against sliding and overturning by the weight of the surcharge and backfill.
Counter-fort/Buttressed retaining walls.
Counterfort walls cantilever walls reinforced with monolithic counter forts with the back of the base slab and wall slab. Counterforts are tension stiffeners that connect the wall slab to the base to reduce shearing and bending stresses. For high walls with a height greater than 8-12 m, counterforts can reduce the bending moments.
Wall with cantilevered design
Cantilevered walls are made of an internal stem of cast-in-place concrete, steel-reinforced or mortared brickwork (often in an inverted T shape). These walls cantilever loads, similar to beams, to a large structural footing. They convert horizontal pressures from the wall to the ground below by converting vertical pressures to the ground below. To improve their resistance to high loads, cantilevered walls may be buttressed at the front or have a counterfort at the back. Buttresses are short wings that run parallel to the main wall trend.
These walls need concrete footings that are rigid and below the seasonal frost depth. This wall requires less material than traditional gravity walls.
Reinforced soil retention wall
Steel or aluminum are used to make mechanically stabilized earth walls.GeoTextiles Soil reinforcements are soil layers that have been placed within a controlled, granular fill. Reinforced soils may also be used to erect retaining walls if they are incorporated into the design.
Wall of soil nails
A soil nailed wall is a method of strengthening the soil in an area that has been excavated. This is done by using passive bars, which work in tension. They are generally parallel to each other and slightly inclined down. These bars can be used partially to bend and shear. Nails are held in tension by skin friction between soil and nails.
An anchored wall can be built in any of these styles, but it also has additional strength thanks to cables or other stays anchored in the soil or rock behind it. Boring is used to drive the anchors into the material. The cable’s end is then expanded by either mechanical means or by injecting pressure concrete. This expands the soil to create a bulb. This method, although technically complex, is extremely useful when high loads are expected, or the wall needs to be thin and not too weak.
Wall with sheet piled
Piling is an earth retention and excavation support method that retains soil. It uses interlocking edge sheet sections. Pile is a temporary wall or certificate wall driven into an excavation or slope to support soft soils’ collapse from the higher ground down to the lower ground. It is lightweight and resistant to driving stress. Sheet piles can be reused many times and have a long service life above or underwater, with minimal protection. It is easy to adjust the length of the pile by bolting or attachment. Joints are less likely to be damaged during driving.
Pile wall (tangent piles, secant piles)
The interconnection of concrete piles forms these walls—these piles square measure created by augering and victimization lubricator. The secant piles overlap by approximately three inches. The tangent pile walls are another option where the piles don’t overlap. These piles are flush with each other. The key advantage of secant and Tangent walls is their exaggerated alignment flexibility. Because the walls might be combined, they may have exaggerated stiffness. This means that construction is less hectic. The disadvantages of waterproofing include difficulty in getting at joints and higher prices. It is also difficult to reach vertical tolerances for deeper piles.
Berliner wall (soldier pile).
This wall was used to dig deep into the earth and was a proverbial tool for Roman military engineers. It is relatively inexpensive, easy to build, and simple. It is only suitable for temporary construction and cannot be used in conditions of high formation without extensive dewatering. It is less stiff than other types of retentive walls.
Wall for soil nailing
It is possible that soil nailing will not strengthen or reinforce existing ground. This involves putting in bars that are closely spaced into slopes or excavations to generate construction income. Soil nailing can be used to construct walls to support excavations, hill cuts, bridges, and other high-value projects. This method works in all soil types, including cohesive soil, broken rock and sedimentary rock. This wall is used to stabilize railroad and road cut slopes and excavating retentive structures in urban environments for high-rise buildings and underground facilities. It can also be used to create tunnel portals on steep, unstable and stratified slopes. It is retrofitting and developing of bridge abutments that have advanced boundaries, which include wall support beneath heaped-up foundations.
Wall of bored piles
Bored pile retaining walls can be constructed by connecting a series of bored piles and then excavating the soil. The bored pile retaining walls may contain earth anchors and reinforcing beams. They can also include soil improvement operations, shotcrete reinforcement layers, and soil improvement operations. This construction method is used in situations where sheet piling is not feasible, but the vibration and noise generated by a pile driver are unacceptable.
Wall for mechanical stabilization
Walls made of mechanically stabilized earth (MSE) are walls that can tolerate differential movement. The wall’s face is filled with granular soil, while the backfill soil is retained. MSE walls are easy to construct and do not require any formwork or curing. MSE walls can be constructed by nipping soil into the soil. This involves attaching a slender steel reinforcing bar to the soil. They are placed on a slight slope and grouted into their place. Anchored earth walls
A crib wall is a structure that interlocks concrete, steel, or timber cages or boxes.
Green retaining walls
To retain gentler slopes, green retaining walls are an option. A geocellular structure like a series ‘honeycomb cell’ can be embedded in the surface to stabilise the slope. The individual cells can then be planted.
Barrette retaining walls
Barrette retaining walls are made from reinforced concrete columns in a rectangular form with a long retention direction.
Retaining walls serve three main purposes: to prevent soil erosion, create usable beds from steep terrain, and provide functional or decorative landscaping features. These walls can be built as an independent structure or part of larger construction works, such as a building. Planning permission is required if the wall is more than 1 m high and is located next to a road, pathway, or other structure. Building regulation approval may not be required for freestanding retaining walls; however, all structures must be sound and well-maintained.