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Driven piles are the most common foundation solution used in bridge construction (Paikowsky et al., 2004). Their safe use requires to reliable verification of their capacity and integrity. Dynamic analyses of driven piles are methods attempting to obtain the static capacity of a pile, utilizing its behavior during driving. Dynamic equations (aka pile driving formulas) are the earliest and simplest forms of dynamic analyses. The development and the examination of such equation tailored for MnDOT demands is presented. In phase I of the study reported by Paikowsky et al. (2009, databases were utilized to investigate previous MnDOT (and other) dynamic formulas and use object oriented programming for linear regression to develop a new formula that was then calibrated for LRFD methodology and evaluated for its performance. This report presents the findings of phase II of the study in which a comprehensive investigation of the Phase I findings were conducted. The studies lead to the development of dynamic formulae suitable for MnDOT foundation practices, its calibrated resistance factors and its application to concrete and timber piles. Phase II of the study also expanded on related issues associated with Wave Equation analyses and static load tests, assisting the MnDOT in establishing requirements and specifications.

The state and many counties throughout Minnesota are using a variety of subgrade stabilization techniques for various materials used in road construction. Such methods appear to improve constructability and lead to increased performance and reduced maintenance. While a number of studies have investigated such stabilization efforts (including materials and techniques, relative increases in strength and/or stiffness, etc.) no overall quantification and summary of the effects of material stabilization have been brought forward with recommendations of parameters to be used for design purposes. Although these techniques and materials are commonly used, minimal information has been obtained relating to the Mechanistic-Empirical (ME) properties of these improved materials such that the more cost-effective designs can be implemented. Not having recommendations for the ME properties of the improved materials, the designer is forced to use values for the non-stabilized material. While this does likely lead to extended road life, costs could be greatly reduced by taking advantage of the improved properties of the stabilized roadway materials. This project has involved determining which types of subgrade stabilization are being used, identifying which of these stabilization techniques/materials are of interest to the Minnesota Department of Transportation (MnDOT), compiling the results of past research relating to these stabilization techniques, summarizing the results of past research and proposing a mix design procedure that obtains material properties for use in design. This proposed mix design procedure will allow the designer to account for improved stiffness due to stabilization, reducing costs and improving the efficiency of the design.

A custom application "app" has been created for use on "smart devices" (phones and tablets on iOS and Android platforms) that will allow users to easily access MnDOT geotechnical asset information in the field. Through the app, users can access MnDOT foundation boring metadata and download PDF files of boring logs of interest. In addition to the development of a mobile-friendly tool [supplementing an existing website], this research effort is partly to determine a proof-of-concept related to development time, effort, documentation, and interdisciplinary coordination for development of similar systems. Through this tool, an interactive map, using boring GPS locations, or search queries, will allow improved access to subsurface information in the field in real time. This will provide a broader benefit to consultants, contractors, local units of government, researchers, and other groups especially when making decisions on-site and in the field (i.e., project scoping, site review, construction inspection, forensic analysis, etc.) This effort builds on efforts to create a data warehouse of geotechnical information and make it more easily sharable and useful to the engineering community.

The current test rolling program as used by Mn/DOT is in need of an update and/or supplement to existing equipment, procedures and specifications. The traditional roller is very heavy and cumbersome and the current construction specification is not technically based. Due to the heavy weight, the roller is only appropriate in approving lifts that are three to four feet thick. While this is ideal for large projects where thick lifts are to be evaluated, most projects do not need this magnitude of loading. This implementation project has developed a more adaptable test roller system and an appropriate construction specification for this modified system. The new test roller and construction specification allow for variation in the weight applied, which will allow varying site conditions to be tested. Such a system would be especially appropriate for roadways that are designed for less than 10 ton loads. This system is easily transported, such that mobilization will be more efficient, and data are continuously recorded during test rolling. The modified test roller is an instrumented system mounted on a standard dump truck. A new test specification has been proposed for the new system and deflection criteria have been established for several combinations of subgrade types and roller weights. The results of the project have also provided a method for comparing pavement structures and layer properties as constructed to their intended design, linking roller deflections to pavement performance. The new system has been utilized on several regional projects and has been shown to work effectively.

Driven piles are the most common foundation solution used in bridge construction across the U.S. Their use is challenged by the ability to reliably verify the capacity and the integrity of the installed element in the ground. Dynamic analyses of driven piles are methods attempting to obtain the static capacity of a pile, utilizing its behavior during driving. Dynamic equations (a.k.a. pile driving formulas) are the earliest and simplest forms of dynamic analyses. Mn/DOT uses its own pile driving formula; however, its validity and accuracy has not been evaluated. With the implementation of Load Resistance Factor Design (LRFD) in Minnesota in 2005, and its mandated use by the Federal Highway Administration (FHWA) in 2007, the resistance factor associated with the use of the Mn/DOT driving formula needed to be calibrated and established. The resistance factor was established via the following steps: (i) establishing the Mn/DOT foundation design and construction state of practice, (ii) assembling large datasets of tested deep foundations that match the state of practice established in the foregoing stage, (iii) establishing the uncertainty of the investigated equation utilizing the bias, being the ratio of the measured to calculated pile capacities for the database case histories, (v) calculating the LRFD resistance factor utilizing the method's uncertainty established in step (iv) given load distribution and target reliability. The research was expanded to include four additional dynamic formulas and the development of an alternative dynamic formula tailored for the Mn/DOT practices.

To expedite more rapid construction of bridges, it has been customary in many states to ignore setup effects when predicting pile group capacities. End of driving capacities have frequently been used as the design capacity for a pile group. For many soil profiles, setup yields pile groups that have significantly higher capacities after some amount of time when compared to the capacity immediately after driving. In order to meet the immediate capacity requirements, piles are often driven deeper than necessary in order to obtain some desired capacity at the time of pile driving, even though substantial increases in capacity may develop in the days and weeks following driving. Being able to perform in situ or laboratory tests that can predict the magnitude and/or rate of pile setup during the design stage would provide a much more efficient pile design, since the cost of materials and the construction time required to drive the piles would decrease. Piles could be driven to a lower capacity, knowing that after an anticipated amount of time the capacity would increase to the desired target capacity, and restrike analyses could be performed to verify this capacity. This study has investigated the side shear setup phenomenon and various methods of predicting the magnitude and/or rate of setup. This was done by means of conducting a literature review and a survey of transportation agencies. Several methods have been proposed for dealing with the setup phenomenon and these methods are described briefly in the body of this report.