The number of current standard foundation options for bridge substructures is limited thus reducing the potential time savings afforded through newer, less-common technologies. Though acceleration of bridge projects has greatly progressed, the potential for additional time savings still exists through the use of other methods such as helical piles. In addition to their fast installation, the use of helical piles offers immediate capacity determination upon installation through capacity to torque ratios, and the use of small maneuverable equipment for installation.
Helical pile foundations have become commonplace in new commercial building construction and foundation repair applications with many foundation installers now offering this technology as one of their services. However, few bridge projects have been completed using helical piles despite their high capacities and speed of installation. The required equipment for installation (skid steer, back hoe, or excavator) lends itself to quick deployment and being an economical solution (i.e., excavator vs. crane), an advantage for any bridge project, but particularly for low-volume roads where budgetary considerations tend to be of specific priority. With sufficient investigation, there is high potential for implementation.
The main objective of this project is to enhance the predictive capability of bridge demolition process by developing a computational framework that can efficiently simulate feasible demolition scenarios and take the guesswork out of equation.
The objectives of this project will be achieved via these six tasks:
- Literature Review
- Develop a Design Guide for Helical Pile use on ABC Projects
- Identify Bridge Project for Demonstration
- Collaborate with Design Engineers to Establish Plans and Specifications
- Provide a Summary and Recommendations for Phase 3
- Final Report
- Task 1 – Literature Review
- The completion of Phase I of this project has produced a comprehensive literature review. Additional information uncovered through continued searches during Phase II will be incorporated into the overall review. As before, the main objective of this task is to obtain an exhaustive understanding of helical pile use and its potential application to ABC projects.
- Task 2 – Develop a Design Guide for Helical Pile use on ABC Projects
- To establish the steps that one would be required to complete the design process for helical pile foundations, a design guide will be developed. Although the research team reserves the right to make changes to the specific guide format, it is envisioned the guide will include the following sections:
- Preliminary Design
- Load Application
- Analysis and Design
- At this time it is anticipated the preliminary design section will include the decision making framework developed during Phase I for using helical piles in lieu of another foundation system. Among other things, this framework addresses the lateral and vertical demands associated with conventional highway bridges and draws attention to the limitations of helical piles when used in high seismic regions or in areas susceptible to scour. With respect to loads, contact will be made will several key industry stakeholders and practitioners to explore the maximum capacity of helical piles, and the potential increase thereof, as it is anticipated the foundation loads of larger bridge structures will exceed the load capacity of the most typically used piles. The goal will be to increase capacity without unnecessarily increasing the size of equipment so as to maintain quick mobilization in limited space. In total, this format will present the engineer with all of the information needed to transform ideas into design and contract documents. The manual will be prepared in language familiar to engineers with technical information provided in a form similar to commonly referenced AASHTO documents.
- Task 3 – Identify Bridge Project for Demonstration
- In collaboration with the TAC members from the state and county levels of Iowa, the research team will identify a bridge construction project where helical piles may be used in lieu of traditional foundation types. Since the identified project is likely to have progressed through the preliminary design phase prior to this activity, the decision to use helical piles will be a decision to replace what has already been decided. Despite this fact, the decision matrix developed in Phase I of this study will be used as if the project was first identified as a potential candidate for helical pile use during the early planning stages. This will be done to record how the decision to use helical piles might have been the same or different if the decision matrix was first employed.
- Task 4 – Collaborate with Design Engineers to Establish Plans and Specifications
- The plans and specifications required to construct the bridge foundations will be developed in collaboration with the design engineers. The task will ensure constructability and will aim to include any necessary requirements to emulate a true accelerated bridge construction project. A focus will be on the small size and quick mobilization of equipment, thus the specifications will include size restrictions for equipment, site restrictions where equipment can be located, and time allowances for installation.
- Task 5 – Provide a Summary and Recommendations for Phase 3
- It is anticipated the majority of activity in Phase III will be centered on the observation and documentation of foundation construction activities for the bridge selected in Task 3 of Phase II. Recommendations for Phase III will be offered during this task which may include an evaluation of the contractor’s adherence to the plans and specifications, and a recommendation to hold an organized meeting between the contractor, designer, and owner to discover any lessons learned and potential improvements to the process so as to better develop the process for future installations.
- Task 6 – Final Report
- The project findings from the previously identified tasks will be prepared by means of a final report. This document will include the identified current state-of-the-practice of helical piles, the adoption to an upcoming bridge project, and the recommendations for documentation of construction activities and lessons learned.
- Phase I of this study regarding the use of helical piles in bridge foundations of ABC projects provided preliminary guidance. The guidance was based on information collected to assess the expediency, adequacy, and use of helical piles.
- Phase II of this project aims to implement helical piles as a deep foundation alternative for an ABC project. Phase II will involve the development of a guide, plans, and specifications necessary for the adoption of helical piles for an upcoming bridge project. This implementation will result in a more comprehensive understanding of the benefits and limitations of helical pile use for bridge foundations.
Principal Investigator: Justin Dahlberg
Previous Progress Reports: