United States Department of Transportation
i
Testing Protocol for Predicting Driven Pile Behavior Within Pre-Bored Soil
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2016-02-01
[PDF-26.57 MB]
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TRIS Online Accession Number:01596693
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Edition:Final Report
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Abstract:Piles at a project site derive their load carrying capacity from “side friction” along their embedded lengths as well as from “end resistance.” Pre-boring is a method used to facilitate driving of displacement piles through hard/dense soils. A pilot hole, generally smaller in size than the pile to be installed, is first bored to a specified depth. By pre-boring a pilot hole, the “end bearing” and “side friction” within the pre-bore zone are reduced, thus aiding the driving of the pile. However, pre-boring complicates the prediction of long-term pile capacity (specifically side friction) within the pre-bored zone and the Wave Equation Analysis of Pile (WEAP) analysis, which aims to predict pile drivability. The objective of this project was to compile the state-of-the-art and best practice results available on the subject of pre-bored piles and develop a research and instrumentation testing plan for future field data collection and select multiple pile driving sites representing different soil strengths. Subsurface geologic characteristics of Louisiana were used to recommend multiple pile driving sites for future testing of piles. A plan was recommended for driving multiple test piles at each site using differently sized pre-bored holes with no pre-boring as control for comparison. Instrumentation and monitoring plan utilizing vibrating wire strain gauges or embedded data collector technology during static load test as well as pile dynamic analyzer (PDA) during initial pile driving and restrikes was suggested to be included in the pile testing protocol. The field load testing and instrumentation data obtained during the proposed protocol can be used by the Louisiana Department of Transportation and Development (DOTD) and consulting engineers in evaluating the change in “side friction” capacity of piles while utilizing different size pre-bored hole. The database of information generated from the different sites will help reduce uncertainty in long term pile capacity prediction and constructability issues when using a pre-bored hole for pile installation.
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