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https://www.nationalacademies.org/trb/events

Engineering Assessment of Drive Point Data for Improving the Prediction of Geomaterial Properties and Design & Construction of Pile Foundations

Highway projects require site investigation (SI) to determine subsurface information for engineering designs and constructions. The subsurface information may include geological profile, geomaterial properties, groundwater, bedrock, and any potential subsurface problems. Some common purposes of the SI include (1) the identification of construction materials, (2) design and construction of highway infrastructure, (3) geomaterial sampling and characterization, (4) planning for the construction technique, and (5) determination of potential subsurface concerns. Due to geological uncertainty and inherent variability of natural soil and rock materials, site characterization typically represents a large share of the geological/geotechnical engineering budget (Coduto et al., 2011). SI typically consists of four main parts: (1) antecedent investigation, (2) field investigation, (3) laboratory testing, and (4) technical reporting. Antecedent investigation provides the basis for subsequent field investigation, and field investigation allows in-situ testing and geomaterial/groundwater sampling for laboratory testing. The SI can lead to the largest source of uncertainties in the design and construction of pile foundations (Oluwatuyi et al., 2023). The most cost-effective SI approach suggested by Handy (1980) is the one with a variability consistent with the variability of the subsurface profile. That is, a few precise tests for a uniform deposit and more tests for an erratic deposit. The current field investigation practice of the Wyoming Department of Transportation (WYDOT) Geology Program involves driving a 1¾-inch hollow steel rod with a 2-inch conical tip known as the drive point (DP). Although ASTM standard is not available, the current DP has been implemented by the Geology Program as part of the SI since the 1960s, and different hammer types with varying efficiencies have been used for driving the DP over decades. In the past 10 years, the DP driving has been conducted using a 140-lb automatic hammer mounted on a drill rig and a hammer stroke height of 30 inches. The automatic hammers of the WYDOT Geology Program are calibrated periodically, and the hammers have efficiencies of more than 90% (Hannigan and Klesney 2017). DP blow count is recorded every one-foot penetration of DP. The DP blow counts provide a “continuous” profile of the relative denseness of the subsurface, and driving refusal can vary between 30 to 400 blows per foot. The WYDOT Geology Program has been using DP in every SI except for gravel pits and rock quarries. The DP blow count helps geologists and geotechnical engineers to: (1) better understand the subsurface profile through the relative denseness, (2) make a better decision during the field investigation regarding locations or depths of in-situ testing and sampling, (3) identify in-situ test methods, and (4) select drilling methods required to successfully complete a test hole. On the other hand, the DP measurements are not intended for determining rock rippability, soil types, rock lithology, nor bearing capacity of geomaterials. For a project site, DP is often conducted first to understand the subsurface profile and condition before drilling more boreholes, conducting Standard Penetration Test (SPT), and collecting undisturbed soil samples using a thin-wall Shelby Tube. Although borehole drilling can provide a continuous log of the lithology, it can be hard on determining pile refusal depths, settlement zones, and other subsurface problems. SPT is often conducted at every 5 ft and can only provide a discrete snapshot of subsurface conditions. In addition, Shelby-tube sampling is often conducted at the mid-depth of a soil layer for a length of 1 to 2 ft. Although the Cone Penetration Test (CPT) provides a continuous measurement of soil properties, a smaller conical tip of CPT is not suitable for a typical subsurface with boulders, cobbles, and hard gravelly layers in Wyoming. The overall goal of the proposed research is to improve the performance of transportation infrastructures in Wyoming. Recognizing the advantages and some challenges with the DP method, this research project is proposed to accomplish three main objectives: (1) improve the understanding of subsurface profiles and conditions; (2) scientifically and statistically develop relationships between DP and geomaterial properties; and (3) improve the design and construction of driven piles using the DP method. The proposed research will have the following outcome measures: (1) SI performances: The proposed DP method will improve the overall performance and effectiveness of the SI. The proposed DP method will improve the understanding of subsurface conditions and allow for better decisions on subsequent geotechnical testing and geomaterial sampling. (2) Engineering performances: Equations will be developed to predict geomaterial properties, strength measures, and pile resistances based on DP data. These outcomes will improve the performance of geotechnical engineering design and construction.