What are the main types of mini piling that the contractor usually recommends

Mini Piling Contractors:

Mini piling, also known as micropiling, is a deep foundation solution utilised when traditional piling methods are inappropriate due to limited access, limited headroom, or subtle ground conditions. These piles are normally smaller in diameter than conventional piles and can be installed with minimal trouble. Mini Piling Contractors usually recommend types of mini piling based on the project’s exclusive requirements, soil conditions, and structural loads. The main types of mini piling consist of:

1. Driven Mini Piles
2. Screwed (Helical) Piles
3. Drilled Mini Piles
4. Grouted Mini Piles

Driven Mini Piles

Driven mini piles are installed by driving prefabricated steel, concrete, or timber sections into the ground using a hydraulic hammer or similar equipment. This method is often preferred for its speed and cost-effectiveness, particularly in cohesive soils where minimal displacement is required. There are several subtypes:

Steel Tubular Piles:

These are thin-walled steel tubes driven into the ground and then filled with concrete. They provide high strength and are suitable for sites with limited access.

Precast Concrete Piles:

Precast concrete sections are driven into the ground, offering high durability and resistance to corrosion. However, they require careful handling to avoid damage during installation.

Timber Piles:

Used less frequently, timber piles are suitable for temporary structures or in environments where timber is readily available and economically viable.

Advantages:

• Quick installation process
• Immediate load-bearing capacity
• Appropriate for a wide variety of land conditions

Disadvantages:

• Can cause vibrations and noise
• Not ideal for sensitive or urban areas

Screwed (Helical) Piles

Screwed piles, also known as helical piles, consist of steel shafts with helical plates welded along their length. They are attached to the earth using hydraulic torque motors. This method is particularly effective in loose, granular soils and areas with limited access.

Advantages:

• Minimal ground disturbance and vibrations
• Can be suitable and installed in every type of soil
• Load capacity can be adjusted by changing the helix size and shaft diameter
• Installation can be reversed if needed

Disadvantages:

• Limited depth of installation due to torque limitations
• Potential for damage to the helical plates in very dense or rocky soils

Drilled Mini Piles

Drilled mini piles are installed by drilling a borehole into the ground, which is then filled with reinforcement and concrete or grout. This type is often used in situations where ground conditions are too hard or rocky for driven piles.

Types of Drilled Mini Piles:

Rotary Bored Piles:

A rotating drill makes a borehole, which is then filled with concrete. This method is suitable for dense, cohesive soils.

Continuous Flight Auger (CFA) Piles:

A continuous auger drills the pile, which is then filled with concrete as the auger is withdrawn. This method is quick and provides excellent load-bearing capacity.

Advantages:

• Can penetrate hard ground and rock
• Minimal vibration and noise, suitable for urban environments
• Precise control over pile placement

Disadvantages:

• Slower installation compared to driven piles
• Requires specialised drilling equipment

Grouted Mini Piles

Grouted mini piles involve drilling a small-diameter hole and injecting grout under pressure. The grout reinforces the soil and bonds with the pile, enhancing its load-bearing capacity. Grouted piles are often used in weak or unstable soils where additional support is required.

Types of Grouted Mini Piles:

Compaction Grouted Piles:

Grout is injected to compact and stabilise loose soil around the pile.

Jet Grouted Piles:

High-pressure jets inject grout to mix with and improve the surrounding soil.

Advantages:

• Effective in reinforcing weak or unstable soils
• Can be installed in restricted-access areas
• Provides good load-bearing capacity and stability

Disadvantages:

• More expensive and time-consuming due to the need for precise grouting
• Requires specialised equipment and expertise

Selection Criteria

The choice of mini piling method depends on several factors:

Soil Conditions:

The type and situation of the soil are serious and important. For example, driven piles work well in cohesive soils, while drilled or grouted piles are better for hard or rocky ground.

Load Requirements:

The structural load the pile needs to support will influence the choice. Helical piles can be adjusted for load by altering their design, while driven piles offer immediate load-bearing capacity.

Site Access:

Limited access or low headroom may necessitate using compact, mobile equipment, making drilled or screwed piles more suitable.

Environmental Impact:

Urban areas or environmentally sensitive sites require methods that minimise noise and vibration, favouring drilled or grouted piles.

Cost and Time Constraints:

Budget and project timelines will also influence the decision. Driven piles are often quicker and cheaper to install, but site conditions and environmental concerns may require more expensive and time-consuming methods.

Conclusion:

Mini piling offers multipurpose solutions for many foundation challenges, particularly in compelled or sensitive environments. By carefully measuring soil conditions, load requirements, site access, environmental impact, and cost considerations, contractors can choose the most suitable Mini Piling Kent method to ensure a stable and hard-wearing foundation.