Auger Cast Pile Design

Step-by-Step Design Process of Auger Cast Piles (ACP)

The design process for Auger Cast Piles (ACP) follows a structured approach to ensure the stability and performance of the deep foundation system. Here’s a detailed overview based on the guidelines provided by FHWA-HIF-07-03.

photo of a foundation rig drilling an auger cast pile

Auger cast pile installation

Initial Design Considerations

1. The first step involves a thorough review of structure-specific and site-specific conditions.

This includes understanding the soil characteristics, load requirements, and environmental factors affecting the project. Accurate assessment at this stage is crucial for the success of the auger cast pile foundation system.

2. Comparison and Selection of Deep Foundation Alternatives

Before choosing auger cast piles, it’s important to compare it with other foundation alternatives. This might include ground improvement techniques that could support shallow foundations since the goal is to select the optimum foundation system for the specific project conditions.

3. Selection of Pile Length and Assessment of Pile Performance

This step involves determining the appropriate pile length and evaluating its performance under specified loads. The design follows the Allowable Stress Design (ASD) method for geotechnical conditions, applying a factor of safety to ultimate limit state conditions to derive allowable resistance values.

Key tasks include:

  • Calculation of Pile Length
    • Estimating the required pile length based on soil conditions and load requirements for auger cast piles.
  • Verification of Capacity and Performance
    • Ensuring the pile can withstand axial and lateral loads.
  • Pile Group Capacity and Settlement Calculations
    • Assessing the performance of pile groups and their expected settlement.
  • Pile Structural Design
    • Designing the pile structure in accordance with Load and Resistance Factor Design (LRFD) principles.
  • Miscellaneous Considerations
    • Addressing other relevant factors affecting auger cast piles performance.

4. Review of Constructability

A final review of constructability is essential. This involves evaluating various factors such as pile length and diameter, penetration into bearing strata, soil mining risk, potential effects on nearby structures, feasibility of the construction sequence, and any other project-specific construction issues related to auger cast piles.

5. Preparation of Plans and Specifications

The last step is preparing detailed plans and construction specifications. This includes setting quality control and quality assurance (QC/QA) measures and defining load testing requirements. Clear and comprehensive documentation ensures all stakeholders are aligned and the construction process for auger cast piles proceeds smoothly.

By following these steps, engineers can design efficient and reliable auger cast piles that meet project requirements. The systematic approach ensures that auger cast piles are a suitable and effective solution for deep foundation needs.

Design Resource

FHWA Design and Construction of Continuous Flight Auger Piles, GEC#7