What is Dynamic Compaction?
Dynamic Compaction is used when there are limitations underground that make it difficult to compact the soil in other ways. It’s a technique where a heavy weight is dropped repeatedly to make the soil denser and fill any gaps. Repeated surface tamping of the ground is done with a large steel or concrete weight. The tamper typically weighs 5 to 10 tonnes and descends in free fall from a height of 10m.
The tamper is dropped multiple times across the location to create a pass in a grid pattern. A site may need 2 or 3 passes, depending on the kind and state of the soil. Granular material is deposited into the impressions created at every drop spot following each pass.
What are the Types of Dynamic Compaction?
Three types of Dynamic Compaction are most frequently used, which are mentioned below:
Dynamic Impact Compaction (DIC)
One dynamic compaction technique called DIC involves lowering a weight from a crane onto the ground. The kind of soil, pounder weight, and drop height all affect how deep the treatment is applied. The maximum depth is around 12 meters, although it varies based on operational factors and soil properties. Different passes are required because DIC tends to loosen the top layers of the soil while compacting the deeper ones.
Rapid Impact Compaction (RIC)
A hydraulic hammer is used in the Rapid Impact Compaction (RIC) surface compaction process on a steel foundation. The impact frequency can range from 40 to 80 times per minute, and the hammer’s weight and diameter can also be adjusted. The material, soil stratification, footing size, and impact frequency affect how deep an impact occurs. Productions occur in the 1,500–5,000 m2/12-hour range, and the best configuration and dimensions must be tested.
High Energy Impact Compaction (HEIC)
A surface compaction technique called High-Energy Impact Compaction (HEIC) uses towed steel drums to repeatedly contact the ground surface with high force. Granular soils and clayey subgrades are their ideal uses. The process can produce 6000–9000 m2/12 hours at a maximum treatment depth of 1.5–2.5 m.
Why is Dynamic Compaction Necessary?
Ground Improvement: Dynamic compaction enhances soil’s load-bearing capacity and overall stability.
Settlement Reduction: Dynamic compaction reduces settlement potential by densifying soil, preventing excessive settling of structures built on treated ground, which is crucial for large-scale infrastructure projects.
Risk Mitigation: Dynamic compaction reduces settlement and improves soil stability, reducing risks of unevenly settling structures, structural damage, and safety concerns, especially in areas with subsidence or strict structural integrity standards.
Speed of Execution: Dynamic compaction is relatively quick, making it advantageous for projects with tight schedules. The dynamic compaction equipment rapidly applies energy to the soil, leading to swift consolidation and improvement in soil characteristics.
Versatility: Dynamic compaction is a versatile technique that can be applied to various soil types and geological conditions, addressing specific challenges of different soil compositions.
Pros & Cons of Dynamic Compaction
There are various advantages and disadvantages of Dynamix compaction, but only a few are mentioned below:
Pros
- Effective in a range of soil types.
- Effective enhancement without requiring a lot of digging.
- Improves stability by reducing soil liquefaction.
- Expands the soil’s carrying capacity for sturdy foundations.
- By reusing the current soil, landfill waste is decreased.
- Reduces post-construction settlements to promote stability throughout time.
- Ecologically sustainable, with minimal impact on the environment.
Cons
- Limited access to underground services and buildings.
- Not suitable for water depths below 1.5 meters.
- Difficult to apply on soils with soft upper-layer and cohesive soils.
- Ineffective if the permissible content of the soil exceeds 20%.
- Complicates matters further by requiring a comprehensive in-situ testing program.
What are the Applications of Dynamic Compaction?
- Dynamic compaction enhances soil for construction by improving load-bearing capacity.
- It is employed in land reclamation to stabilise soil in waterlogged areas.
- Airport runway construction benefits from dynamic compaction, ensuring a solid base for heavy aircraft loads.
- This technique prepares a stable subgrade in road construction, capable of withstanding traffic loads and minimising settling.
- Dynamic compaction is utilised in earthquake-prone areas to mitigate liquefaction risks by consolidating loose, saturated soils.
Conclusion
Dynamic compaction is a ground improvement technique to increase soil density in areas with limited subsurface access. It involves a drop weight and repeated surface tamping with a large steel and concrete weight. Three types of dynamic compaction are Dynamix Impact Compaction (DIC), Rapid Impact Compaction (RIC), and High Energy Impact Compaction (HEIC). It enhances soil load-bearing capacity, reduces settlement potential, mitigates risks, and offers speed. For further information, don’t hesitate to contact us on this no. 0800 193 9090 or visit our website, “Southern Foundations & Piling.”