How to Maximise Screw Piling in Challenging Soil Conditions

July 24, 2023

Screw piling is a versatile foundation system that is carried out by installing screw-like helical piles into the ground, providing structural support for buildings, structures, and other similar construction projects. This system offers numerous advantages like ease of installation, cost-effectiveness, and minimal site disruption. 

But one unique benefit of screw piling that other foundation methods do not maximise is its ability to create a foundation in areas with challenging soil conditions. You see, these areas can often affect the performance, load-bearing capacity, and other aspects of most foundation methods. Screw piling, however, can still provide its previously stated benefits without any issues, as long as it is carried out carefully and properly.

Here are some common challenging soil conditions that can be applied with screw piling.

Soft Soils

Soft soils like clay and silt can somehow pose challenges for screw piling due to their low shear strength and high compressibility. In such conditions, one should consider the potential for excessive settlement. Designing the screw pile system with adequate pile spacing and length can effectively distribute loads and minimise cases of settlement.

Expansive Soils

Expansive soils like clayey soils with high shrink-swell potential can cause significant movement and heave, affecting the stability of foundation systems. To address this challenge, the soil’s moisture content and potential for volume changes should be assessed. Fortunately, accommodating soil movement through implementing proper drainage measures and designing the foundation system can mitigate the effects of expansive soils.

Collapsible Soils

Collapsible soils can be often found in arid regions. These soils are known for undergoing significant volume reduction when subjected to moisture changes, which leads to ground subsidence and structural instability. One way to ensure successful screw piling is to evaluate the soil's collapsible potential and consider appropriate moisture control measures like soil stabilisation or pre-wetting. Doing these can prevent collapse and ensure foundation stability.

Sloping or Hilly Terrain

When working on sloping or hilly terrain, additional considerations must be considered to maintain stability and prevent soil movement. Proper slope analysis, anchoring techniques, and retaining structures may be done to secure the integrity of the screw piling.

Groundwater

Groundwater conditions can hugely impact the performance of screw piles. High groundwater levels can affect the installation process as well as reduce their load-bearing capacity. The implementation of dewatering systems or incorporating appropriate drainage measures can be effective in managing groundwater and guaranteeing stable conditions for screw piles.

Seismic Zones

Areas prone to seismic activity may be bombarded with dynamic forces during earthquakes. Hence, proper seismic analysis, consideration of liquefaction potential, and reinforcement measures like helical pile configurations and seismic bracing should be carried out to enhance the screw piling system’s resistance to seismic loads.

Sand and Gravel

Sandy or gravelly soils can present difficulties during foundation installation due to their loose and granular nature. The screw piles may even experience loss of torque or resistance during installation, resulting in reduced load-bearing capacity. Pre-drilling or jetting techniques can be carried out to facilitate pile installation and boost the bearing capacity in these soils. While challenging soil conditions can present obstacles to construction projects, screw piling remains a viable foundation solution with the potential for successful implementation. By considering the specific soil challenges, implementing suitable design measures, and applying appropriate installation techniques, screw piling can provide reliable and efficient foundation support in a wide range of soil conditions.

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