Introduction
Piles can be categorized into two main types based on construction methods: precast piles (prestressed pipe piles) and bored piles (drilled cast-in-situ piles). Both are widely used in soft soil foundations with thick overburden, offering high bearing capacity, stability, minimal settlement, and material efficiency. They effectively meet structural requirements for foundation strength, deformation, and stability.
Each pile type has distinct characteristics, employing different machinery, construction techniques, and soil interaction mechanisms, leading to varying suitability. This article compares these two pile types, analyzing their advantages, disadvantages, and applications to determine whether prestressed pipe piles or drilled cast-in-situ piles are more suitable for specific projects.
Prestressed Pipe Piles
Prestressed pipe piles are hollow cylindrical precast concrete members manufactured using pre-tensioning techniques, high-efficiency water reducers, and high-speed centrifugal steam curing. They consist of a cylindrical pile body, end plates, and steel hoop reinforcements.
Drilled Cast-in-Situ Piles
These piles are constructed on-site by drilling into the soil, removing excavated material, placing reinforcement cages, and pouring concrete into the borehole.
Comparative Analysis: Prestressed Pipe Piles vs. Drilled Cast-in-Situ Piles
1. Mechanism of Action
Prestressed Pipe Piles:
- Installed by driving or pressing into the ground, causing soil compaction.
- A short-term increase in pore water pressure leads to soil heaving and lateral displacement.
- It may affect nearby structures, roads, and existing piles, causing deformation or uplift.
Drilled Cast-in-Situ Piles:
- Constructed using dry or slurry-supported drilling, minimizing soil disturbance.
- No excess pore water pressure buildup, making them safer for adjacent structures.
- Advantages: No vibration, no soil displacement, minimal impact on surroundings.
- Disadvantages: Lower concrete strength, reduced single-pile bearing capacity, higher settlement.
2. Construction Conditions
Prestressed Pipe Piles:
- Suitable for soft soils, sandy soils, plastic soils, silt, and loose gravel (without large boulders).
- Difficult to penetrate thick sand layers or hard strata; best for shallow, strongly weathered rock layers.
- Requires large machinery (pile drivers, cranes), needing ample construction space.
Drilled Cast-in-Situ Piles:
- Applicable to sandy, clayey, gravelly, and rocky strata.
- Challenging in淤泥 (soft mud) or areas prone to sand boils/artesian pressure.
- Advantages: Simple equipment, flexible operation, suitable for confined spaces.
- Disadvantages: Longer construction time, less consistent quality control.
3. Construction Process
Prestressed Pipe Piles:
- Survey & Positioning – Mark pile locations.
- Pile Alignment – Align the pile tip with the marked position.
- Pressing/Driving – Apply pressure until the desired depth.
- Splicing – Join additional sections if needed.
- Termination – Stop when the design load capacity is reached.
Drilled Cast-in-Situ Piles:
- Borehole Drilling – Use rotary drilling with slurry support.
- Reinforcement Cage Installation – Lower the steel cage into the hole.
- Concrete Pouring – Use the tremie method for underwater placement.
- Curing & Demolding – Ensure proper strength development.
4. Cost Considerations
- Prestressed Pipe Piles are generally more cost-effective and faster but may require additional measures (e.g., pre-drilling) in rocky conditions.
- Drilled Cast-in-Situ Piles have higher costs and longer timelines but offer greater adaptability.
Conclusion: Which Pile Type to Choose?
The selection depends on:
✔ Soil conditions (soft vs. rocky strata)
✔ Site constraints (space, vibration restrictions)
✔ Project timeline & budget
✔ Environmental impact (nearby structures, noise, vibration)
A thorough comparison based on geological surveys, structural requirements, and economic feasibility ensures the optimal foundation solution.
