Retaining Wall: Definition, Function, and Types of Soil Retaining Walls

In construction, a retaining wall is an essential structure used to maintain soil stability so that it does not slide or shift.

In Indonesia, which has high rainfall and many hilly areas, the presence of these soil-retaining walls is not just an accessory, but a primary necessity. To help you understand better before building or buying a house, let's discuss it!

What is a Retaining Wall?

Simply put, a retaining wall is a structure designed to resist the lateral pressure of the soil behind it. It is usually used on sloped land, cliffs, basements, or terraced areas.

This structure is specifically designed to withstand soil pressure, especially during the rainy season when the soil becomes heavier due to water absorption. Without a proper retaining system, the soil can shift and cause anything from minor landslides to structural damage to buildings.

In modern housing projects, retaining walls are often found in:

• Terraced garden areas

• Carports with different elevations

• House basements

• Hilly housing developments

• Boundary walls of sloping lots

Unlike ordinary walls, retaining wall construction must undergo structural calculations. Even a slight design error can lead to cracking, tilting, or even collapsing, especially during heavy rains.

Functions of a Retaining Wall in Construction

There are several important roles that make this structure vital:

1. Preventing Landslides The main function of a retaining wall is to maintain soil stability, especially on land with a certain slope.

2. Ensuring Building Safety Unrestrained soil pressure can damage a house's foundation. With a retaining wall, the risk of structural shifting can be minimized.

3. Managing Land Layout Retaining walls allow you to create neater and more functional terraced land. Sloped areas can be transformed into gardens, patios, or outdoor seating areas.

4. Enhancing Aesthetics Besides being functional, a retaining wall can also serve as a landscaping element. Materials like natural stone or exposed concrete can provide a modern and natural look.

How Does a Retaining Wall Work?

Basically, a retaining wall is a structure designed to withstand the horizontal pushing force of the soil. The soil behind the wall exerts pressure due to its own weight and additional loads (surcharge loads) such as rainwater or buildings on top of it.

To prevent it from collapsing, a retaining wall design considers:

• The weight of the structure itself

• A drainage system to reduce water pressure

• A strong foundation

• The inclination angle of the wall

Drainage is crucial. Without a proper water disposal system, water can get trapped and increase hydrostatic pressure, which can potentially cause the wall to crack or collapse.

Therefore, in good housing projects, a water channel system is always part of the retaining wall structure design.

Types of Retaining Walls There are several types of retaining walls commonly used in Indonesia. The selection depends on soil conditions, wall height, and project needs.

1. Gravity Retaining Wall This type relies on the weight of the structure to withstand soil pressure. It is usually made of massive concrete or river stone. Suitable for:

• Low to medium height walls

• Home garden areas

• Housing with mild contours

2. Cantilever Retaining Wall Uses a base slab system and reinforced concrete. The design is more efficient for greater heights. Suitable for:

• Large-scale housing projects

• House basements

• Commercial areas

3. Sheet Pile Retaining Wall Usually used in areas with soft soil or near bodies of water. The material can be steel, precast concrete, or wood.

4. Counterfort Retaining Wall Similar to a cantilever, but equipped with additional support structures at the back to increase strength.

5. Mechanically Stabilized Earth (MSE) Wall Uses a soil reinforcement system with geogrids or other synthetic materials.

For middle-class urban housing, the gravity or cantilever types are usually used because they are more practical and economical.

Main Components of a Retaining Wall To be clearer, here are the important components in retaining wall construction:

• Base Slab: The main foundation that distributes the load to the ground.

• Stem: The vertical part that directly withstands soil pressure.

• Heel and Toe: The base parts that help stabilize the structure.

• Drainage System: Pipes or weep holes to reduce water pressure.

• Backfill: The fill soil behind the wall that must be compacted correctly.

Factors Influencing Retaining Wall Design Retaining wall design cannot be done arbitrarily. There are several important factors to consider:

1. Soil Type Clay, sand, or rocky soils have different characteristics in bearing loads.

2. Wall Height The higher the wall, the greater the pressure it has to withstand.

3. Surcharge Loads (Additional Loads) The presence of buildings, vehicles, or gardens on the soil behind the wall will add to the load.

4. Rainfall In Indonesia, with its intense rainy season, the drainage system must be well-designed.

5. Budget Materials like reinforced concrete certainly have different costs compared to river stone.

If you plan to buy a house in a hilly area, don't hesitate to ask the developer for details about the soil-retaining structures. Good housing developments are usually transparent about structure and safety.

Differences Between Retaining Walls, Taluds (Embankments), and Gabions Many people still think retaining walls are the same as taluds. However, there are differences.

• A retaining wall is an engineered structure specifically designed with structural calculations.

• A talud (embankment wall) is usually simpler and often uses river stone without a complex reinforcement system.

• Other soil-retaining structures like soil nailing or gabions (bronjong) have different working methods.

Retaining walls are generally used for projects requiring long-term stability and heavy loads, while taluds are more suitable for small-scale or low-risk areas.