Retaining walls, especially those reinforced with steel, provide stable support for structures and landscapes for many years. These powerful structures are designed to withstand soil weight and other forms of pressure, which can cause significant damage if not properly supported.
However, despite a retaining wall’s strength and durability, it is not immune to failure. If it’s subjected to excessive stress or damage, or is improperly maintained, the wall may collapse. In this guide, we’ll explore the signs and causes of retaining wall failure, and how to prevent them:
Signs Of Retaining Wall Failure
Your Wall is Tilting
If you’ve noticed your wall tilting to one side, the contractor may have incorporated inadequate support during construction. For example, when a retaining wall is supported with steel posts, proper positioning and depth are crucial for stability. If posts are not deep enough or are too far apart, it can compromise the wall’s structural integrity to withstand soil weight.
Poor drainage is also a primary cause for walls to tilt. When a large amount of water accumulates behind the wall, it exerts more pressure on the structure, causing it to lean or tilt. In areas where heavy rainfall or flooding is common, it’s worthwhile to invest in proper drainage systems to avoid water accumulation.
Your Wall has Hairline Cracks or Larger Fractures
Wall cracks are reasonably easy to spot – they are visible on your wall’s surface and range from small hairline cracks to larger, more substantial cracks. Unfortunately, while many take action to fix more prominent cracks, many overlook smaller ones that typically indicate an underlying problem.
While larger fractures imply your wall’s structural integrity is failing, smaller cracks grow in size and allow water to penetrate behind the wall. This, in turn, increases the exertion of hydrostatic pressure, weakening your wall over time.
Cracks in retaining walls typically occur by the following:
- Damp or wet soil which adds significantly more pressure than if it was dry. When a flood occurs, it can cause the hillside or area behind the wall to become overwatered. Soil, as a result, becomes heavier and slides easier down your slope, putting more pressure against the wall.
- Excessive load which puts more pressure than what the wall can handle.
- Incorrect design calculations and installation.
- The soil at the base of your wall is sliding or moving.
Your Wall is Beginning to Crumble
Unlike wall cracks that are relatively easy to spot, crumbles in a retaining wall are more challenging to notice until it’s too late. Crumbling happens subtlety and can be missed due to the slow pace at which it occurs.
The first sign of wall crumbling is the presence of your retaining wall’s material and debris at its base. This strongly indicates that the wall is deteriorating and losing its structural integrity, with pieces breaking off and falling to the ground.
Another sign of wall crumbling in concrete retaining walls is exposed rebar. When your concrete sleepers begin to crumble, the steel reinforcement inside becomes visible, accelerating the deterioration process as the rebar begins to rust and corrode. This, in turn, can further weaken the wall’s structural integrity.
Subsidence in Your Wall’s Surrounding Land
Subsidence in your surrounding areas means that the land is sinking. This can occur from soil erosion, compaction or natural geological processes. Human activities, such as underground mining, construction, or removal of underground water can also cause subsidence.
When ground subsidence occurs, it can cause change to the pressure on your retaining wall, leading to structural issues. If the soil on one side of the wall sinks, it can cause uneven pressure, leading to tilting, cracking, or crumbling. Similarly, sinking of land beneath your wall can cause its foundation of the wall, leading to failure.
Remember, your retaining wall’s initial design includes precise calculations which account the current loads and pressures from the surrounding soil, so any change in soil condition, overtime, can impact the wall’s stability.
Causes for Retaining Wall Failure
Besides the signs of retaining wall failure, there are various causes that can lead to the collapse of a retaining wall. These include:
Saturation of backfill
Proper drainage systems ensure inflows of water, whether it’d be from rainfall or irrigation, flows freely from your retaining wall. If water isn’t adequately drained, it saturates your wall’s backfill, creating substantially more pressure than what your wall can withstand long-term.
New, Unexpected Loads from Natural or Planned Events
Your geographical landscape is never stagnant, and unexpected loads can arise from natural or planned events that compromise your retaining wall. Natural occurrences such as landslides or earthquakes can cause sudden and unexpected loads on the wall, while human intervention like a new construction or landscaping changes can do the same.
Incorrect Calculations in The Design
Before a wall is built, a structural engineer calculates the expected loads and pressures on the wall and designs it accordingly. Incorrect calculations or inadequate design can cause your wall to be less structurally stable than it should be, unable to withstand unilateral soil pressure.
Low-quality materials and Poor Installation
A retaining wall is typically installed to provide support against the soil behind it. Using cheap materials, like low-quality concrete blocks don’t last as long and are more likely to fail over time.
Poor installation, meanwhile, such as inadequate soil compaction or misalignment of blocks installed, can compromise the wall’s stability and durability. This can cause your wall to shift or lead, leading to wall failure.
Inadequate Site Inspection
When a new site is inspected, things like soil type, water tables, slope angle, and backfill materials are considered before a wall is built. Building regulations on your wall’s load bearing capacity and height are also considered during site inspection. If the site investigation was performed incorrectly, it could lead to the construction of an unsuitable wall that’s not structurally sound for the specific site conditions.
How to Prevent Retaining Wall Failure
Regular Inspection and Maintenance
It’s important to conduct regular wall inspections to confirm that there are no cracks, bulging, or other signs of instability. If these signs are present, repairs or a wall replacement should be conducted asap.
Similarly with drainage systems, routinely check that water has not accumulated behind the wall. After rainfall, water should be drained through weep holes. If not, your weep holes may be congested or there could be an inadequate aggregate or soil behind the wall.
Consult a Structural Engineer for New Loads
As mentioned previously, human activities like constructing a new building near your wall, resurfacing or adding new weight to the top of the wall can cause increased pressure. If you do intend to make any landscape changes, consult a structural engineer to ensure whatever modifications or additions you are planning do not put excessive pressure on the retaining wall.
Invest in High-Quality Materials Before Construction
When building your retaining wall, you’ll want the most durable products known for their strength and longevity. Look for materials that are specifically designed for retaining walls, such as concrete blocks, natural stone, and galvanised steel posts for structural support.
When To Replace A Retaining Wall
Retaining walls are a great way to protect slopes or create level ground for outdoor spaces. However, over time, these walls may start to fail due to environmental factors such as soil erosion and weathering, or structural issues like poor installation. Knowing the signs of retaining wall failure can help you identify when it’s time for repairs or even replacement.
If your wall is showing the following, you may want to consider a full replacement altogether:
- Large fractures that are immediately noticeable in your retaining wall.
- When your wall is separated from the main structure.
- When your wall is leaning or has a bowed look.
- When your wall is bulging or crumbling, especially towards the base of the wall.
The key in ensuring none of the above occur is regular maintenance and inspection of your retaining wall. By checking for the factors mentioned in this article, you can detect any early signs of damage or instability and address them before they escalate. With greater awareness and the willingness to take action, you will have a retaining wall that will last a lifetime – goodluck!
Trust RWS to Provide High-quality Concrete Sleepers and Steel Posts for Your Retaining Wall
Looking for top-of-the-line materials for your retaining wall project? Look no further than RWS (Retaining Wall Supplies) for steel posts and concrete sleepers in Sydney. Browse through our extensive selection of products online or contact us directly to talk to our experts! Our services are also available in Brisbane, Gold Coast, and Sunshine Coast.