Australia is well-known for having rugged, diverse, and unstable landscapes. All of these factors can increase the risks of landslides, erosion, and rockfalls. Whether you’re planning to build a residential home or a commercial structure, it’s essential to know about the risks of building near or on sloped areas.
One of the key ways to assess the ground structure and load-bearing capacity of your prospective build sites is to invest in the mandated soil test Melbourne engineers recommend. This testing process will enable your engineering team to choose the best building methods for your structure’s foundation. This post explores the more common slope stabilisation methods your geotechnical engineer may suggest.
What is Slope Stabilisation?
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No matter where in Melbourne you’ve decided to build, your geotechnical team may recommend you opt for slope analysis. This will identify any potential risks that will affect the safety of your build.
It’s essential to highlight that building near a slope or hilly area has an increased risk of soil erosion, landslides, and other slope failures. This risk is increased during the rainy seasons. Fortunately, your geotechnical team can assess these risk factors and find building techniques to counter these issues.
These techniques are referred to as slope stabilisation methods. Finding the most effective techniques involves assessing and then addressing water content, soil properties, and general external loads.
Many Slope Stabilisation Methods Well Worth Considering
Slope instability is typically considered to be a significant geotechnical risk. A common example of this is the Thredbo Landslide in 1997, where a combination of extreme rainfall and a leaking water main caused an unstable embankment. This in turn led to the collapse of part of the Alpine Way road, triggering a landslide that swept away two ski lodges. Sadly, 18 people lost their lives.
A failure to address the area’s history of landslides was blamed as a significant contributing factor. To avoid a repeat of this tragedy, your local geotechnical engineering team will do the necessary testing to highlight which slope stabilisation methods will make your build safe and durable. Our team has listed a few of the more common methods they may recommend.
1. Drainage Control
No matter how little rain the area gets, drainage control is crucial for controlling water infiltration into the slope. Doing this can increase the pore water pressure, which in turn reduces the overall soil strength. To counter this, it’s essential to install the right amount and type of surface drains and subsurface drainage pipes.
Alternatively, your engineering team may use retaining walls with built-in drainage to redirect, which means the slope is less likely to collapse when it becomes saturated. This method is extremely useful in areas with excessive rainfall or in areas known for having infiltration problems or those prone to waterlogging.
2. Erosion and Vegetation Control
Sandy slopes without any vegetation are particularly susceptible to landslides and collapse. This is because there are no plants or roots to reduce potential surface erosion. If this is the only risk factor in the area, your geotechnical team may recommend planting grass, deep-rooted trees, and shrubs to reinforce the soil structure and minimise water runoff velocity.
This method will typically be used to stabilise natural slopes and environmentally sensitive regions where the goal is to protect the natural landscape. Builds in conservation areas, parklands, and along riverbanks are typical examples of instances where this option works well.
3. Grading and Reshaping
The angle and shape of the slope also contribute to the risk of slope failure. This can be countered by reducing the overall angle and moving the bulk of the soil mass to create a stable slope. This reshaping process minimises the risk of soil erosion or sliding.
For the most part, this method is often used for slopes or hills with mild instability. Keep in mind that the area and available space will need to accommodate large-scale earthmoving. Developing highway embankments is are common instance where this method is used.
4. Soil Nailing
The process of soil nailing typically involves driving different-sized steel bars directly into the slope at various intervals. Doing this will provide exceptional internal reinforcement. Since the nails are grouted in place, they help to stabilise the soil in the slope. This method is considered to be highly effective in deep excavation sites where standard retaining methods aren’t viable.
5. Retaining Structures
Another common method used around Australia is to install retaining walls. These structures are essentially rigid structures designed to hold back soil, which also provides lateral support to risky slopes and hills. The most popular retaining structures to use include the following:
- Gravity walls
- Cantilever walls
- Anchored walls
This method is commonly used in commercial developments and transportation infrastructure, or on sites where there is no space for grading and reshaping.
Final Thoughts
If your intended build is near a slope or hilly area, you should always consider how excessive rain and soil displacement will affect the safety of your build. Speak to your geotechnical engineer about the most effective method for your area, soil type, and overall climate.
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