Research & Innovation

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NS751: Resistances and associated pile lengths of non-displacement piles using static analysis methods

Problem

On several bridge projects in MN, the non-displacement piles were installed much longer than their estimated lengths. This resulted in costly change orders due to the costs and delays associated with procuring and fabricating additional piling during construction. The purpose of this research will determine the cause of the overpredicted resistances of the non-displacement piles in the project specific subsurface conditions and either recommend modification factors that can be applied to the Nordlund method or recommend another static analysis method such as the Beta or API method to accurately estimate pile lengths.

The research will build off the National Road Research Alliance (NRRA) overpredicted resistance pile research, but unlike the NRRA research, include field tension and compression static load testing at MN sites where piles were installed much longer than their estimated length.  The scope of work will consist of a literature review, a review and analysis of data from applicable projects, and piled driving analyzer (PDA), tension and compression static load testing utilizing MnPILE static load test frames on selected sites, analysis and recommendations. 

Objective

This research is a priority to reduce costly change orders during construction, due to the costs and delays associated with procuring and fabricating additional piling. The research will benefit MnDOT and local agencies to reduce project risks and costs and improve pile design methods.

Previous research

The research will build off several research efforts including:

• The National Road Research Alliance (NRRA) overpredicted resistance pile research, but unlike the NRRA research, include field tension and compression static load testing at MN sites where piles were installed much longer than their estimated length. 
• The Efficacy of Design Methods for Predicting the Capacity of Large-Diameter Open-Ended Piles.  Large diameter piles have diameters of 36 in. or greater.  This project will build on this research by primarily focusing on piles that are 16 in. to 30 in. diameter and include H piles.
• Insights into Plugging of Pipe Piles Based on Pile Dimensions.  This research will try to refine this research by looking at plugged based on soil type and diameter.  The research will refine the plugging predictions of pile between 20 in. and 36 in. in diameter for MN soils.

Short descriptions of previous research:

Title: Efficacy of Design Methods for Predicting the Capacity of Large-Diameter Open-Ended Piles

• Authors: Andrew Rizk Antonio Kodsy , Magued Iskander, and Nikolaos Machairas
• Source: Journal of Geotechnical and Geoenvironmental Engineering, July 2022
• Link: https://doi.org/10.1061/(ASCE)GT.1943-5606.0002824
• Abstract: Large-diameter open-ended piles (LDOEPs) are increasingly being used for support of infrastructure projects. Yet, many of the methods in current use for predicting their capacity are based on studies involving small-diameter piles. The efficacy of eight commonly used pile design methods was explored using a database of 64 load tests on full-scale LDOEPs. Capacities were computed using eight commonly used design methods based on both the standard penetration test (SPT) and cone penetration test (CPT). The calculated capacities were compared with capacities interpreted from load tests using several failure interpretation criteria. The study demonstrated that cone penetration test (CPT)-based methods are somewhat superior to SPT methods, but all methods exhibited scatter between measured and predicted capacities, with the computed capacity off by a factor of two in many load tests. Several plugging conditions were compared for each of these methods. Seven of the eight design methods better predicted pile capacity considering that the piles are unplugged, ignoring contributions of the soil internal friction on the pile inner diameter. These findings suggest that (1) LDOEPs do not plug during static loading, with little contribution of interior skin friction to pile capacity; and (2) LDOEPs do not develop significant end bearing.

Title: Insights into Plugging of Pipe Piles Based on Pile Dimensions

• Authors: Antonio Kodsy and Magued Islander
• Source: Applied Science, March 2022
• Link: https://doi.org/10.3390/app12052711
• Abstract: Preliminary identification of plugging of open-ended pipe piles based on their dimensions, ahead of driving, is explored in this study using data analytics. Piles can be unplugged, plugged, or internally plugged, depending on their dimensions, and geotechnical conditions. Plugging of pipe piles influences both pile capacity and driving behavior; however, the classification assumed at the design time does not always manifest during driving, sometimes resulting in driving difficulties. The relationship between pile plugging and pile dimensions was investigated using a dataset of 74 load tests on pipe piles, where geotechnical profiles were also available. An analytics approach borrowed from data science was adopted. First, capacity was computed using four recognized designed methods considering the unplugged, plugged, and internally plugged conditions. Next, the calculated capacities were compared to capacities measured (interpreted) from static load tests. Finally, voting was employed to identify plugging based on the closeness of the computed capacity assumptions to the interpreted capacity. Most piles were found to be unplugged. A diameter criterion is proposed as a tool to give early insight into the plugging condition of a pile ahead of driving which resulted in a 70 ± 10% accuracy. The proposed criterion was validated once using a dataset of 23 piles with CPT data and a second time using 24 published driving records where plugging records were available and achieved similar accuracy, in both cases. It was concluded that piles larger than ~0.9 m (36 inches) in diameter have a higher likelihood of being unplugged, while piles smaller than 0.5 m (20 inches) have a higher likelihood of being plugged.

Title: Overpredicted Resistances of Non-Displacement Piles in Sands Using Static Analysis Methods

• Author: Mohammadhossein Sadeghiamirshahidi
• Source: Not available- research underway. 
• Abstract: Not available- research underway. 

Expected outcomes

• New or improved decision support tool, simulation, or model/algorithm (software)

Expected benefits

The numbers 1 and 2 indicate whether the source of the benefit measurement is from: 

1. A specific research task in your project that will be measuring this particular benefit, or
2. A separate effort to analyze data provided by the state or local agency involved in this project.

• Construction Saving: (2)
• Estimate costs savings through reduced number of change orders based on calculating average costs and delays of using less accurate vs. more accurate pile lengths in construction projects.
• Decrease Engineering/Administrative Cost: (2)
  • Track the number of engineering hours spent on pile reanalysis and bridge rec and plan updates after project letting.
• Decrease Lifecycle Costs: (2)
• Measure the pile costs saved and subtract this from the initial costs in the LCCA.  
• Environmental Aspect: (2)
• Measure the pile length saved and multiply this by associated environmental costs.
• Safety: (2)
  • Measure the pile length saved and multiply this by associated safety costs.
• User Benefits: (2)
  • Measure the pile length saved and multiply this by the associated user costs.
• Risk Management: (2)
  • Track the decrease in the pile bid item cost from contractors, i.e. their risk.

Technical advisory panel

• Joe Nietfeld- OMRR Geotechnical Section
• Rich Lamb- OMRR Geotechnical Section
• Nick Haltvick- Bridge Office Design Build
• Paul Pilarski- Bridge Office Construction
• Karl Gronvall- Bridge Office Construction
• Dave Conkel or Brian Homan- Bridge Office State Aid