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Experiences with Base Grouted Drilled Shafts in Southern California
DFI SuperPile 2015
The use of base grouting (tip grouting) to enhance the axial capacity of drilled shaft foundations can achieve improvements in economy and reliability for many types of projects and soil profiles. Recent experiences on a range of different bridge construction projects in Southern California U.S.A. illustrate some attractive opportunities for utilizing this technique and some limitations of the method. This presentation provides an overview of various grout systems used and a measure of their respective performance through automated monitoring, instrumentation and load testing results along with some lessons learned.
The Use of Small Diameter-Spun Cast Concrete Piles In Highly Variable Soils
DFI SuperPile 2015
Small diameter spun cast driven concrete pile foundations known as ICP piles were used at a site in St. Petersburg, Florida where deep solution cavities were identified in the subsurface data. These ICP piles are manufactured with steel plates on either end to facilitate splicing. Given the variability of the site, the ability to weld sections of concrete pile together using the steel plates benefited the project in several ways. This presentation focuses on the test pile program that was implemented to ensure the ICP piles could provide the necessary resistance and to determine an appropriate driving system and pile installation criterion. Several challenges were overcome during the program in order to maintain pile integrity while achieving the required bearing resistance within the highly variable subsurface conditions.
Side Resistance Measurement of Large-Diameter Open-Ended Steel Pipe Piles and Design Implications
Axtell, Paul. Muchard, Michael.
Until recently, accurate measurement of static side resistance values for open-ended steel pipe piles driven with impact or vibratory hammers has been difficult or impossible to attain. Accordingly, a thorough evaluation of the computed side resistance relative to the actual side resistance has not been possible. A new method of installing strain gages on the outside diameter of relatively large, open-ended steel pipe piles has been developed that allows the instruments to survive the violent installation involving a large impact hammer and refusal blow counts on bedrock. High capacity Statnamic testing has subsequently been performed on these fully instrumented piles and the distribution of side resistance along the pile length along with the contribution of base resistance can be accurately resolved. Such an approach is considered to be superior to high-strain dynamic testing alone because the demonstrated resistance is not limited by the available hammer energy which is obviously depleted when the pile encounters refusal blow counts. On the basis of these measurements, refined design approaches can be developed along with enhanced understanding of the side resistance developed on the inside diameter of the pile. This paper details a case history for a bridge spanning the Mississippi River in Minnesota where three large-diameter instrumented, steel pipe piles were installed and tested with the Statnamic device. The installation of the strain gage devices, results of the Statnamic tests, and implications for open-ended steel pipe pile design will be presented.
Determination of Unknown Foundation Lengths for Bridges Using Parallel Seismic Testing
Muchard, Michael. Nelson, Jordan.
Florida Civil Engineering Journal 2015
Parallel Seismic (PS) testing to estimate unknown foundation lengths is the most widely applicable Non-Destructive Test (NDT) method used to evaluate foundation lengths of existing bridges. This type of NDT testing has other applications within the theme of sustainability in civil engineering structures. Reusing a bridge foundation and determining long term serviceability of existing bridge foundations are at the very core of this ideal. However, there is great trepidation by the engineering community due to uncertainty in the existing foundations. A thorough evaluation program that includes the Parallel Seismic testing method can reduce this uncertainty. Recently, such evaluations were undertaken at three major bridge sites in Florida where Parallel Seismic testing was used to estimate the unknown foundation lengths in order to reuse existing foundations, extend service life, and evaluate scour potential. The focus of this paper is on the PS testing method, results, limitations, and applicability.
STATNAMIC Load Testing of Strain Instrumented Large Diameter Open End Steel Pipe Piles (LDOEP)
DFI SuperPile 2013
Statnamic (Rapid) load testing is a popular and well suited method for testing open end pipe piles for bridge and heavy civil projects for several reasons. These include: no need for reaction piles, large test load capability, time savings, and cost effectiveness. However, one of the continual challenges in any type of load testing of open ended pipe piles is obtaining measured load distribution along the pile length and at the pile tip via strain gages. Use of embedded strain instrumentation within cast-in-place or precast concrete foundations to determine load distribution during load tests has become quite commonplace; and has lead to great improvements in knowledge of these types of foundations. Instrumentation of these foundation types has its own set of unique challenges, but for driven open ended steel pipe piles, the challenges are on a different order of magnitude. A successful open end pipe pile instrumentation scheme has to surmount enormous design constraints. The externally attached gages must endure a brutal pile installation process as they penetrate deep underground. After surviving the pile driving process, the gages must resist large hydrostatic pressures challenging the robustness of the waterproofing. Only after meeting these adversities, can the load distribution be measured during load testing.
Case histories of the St. Croix River Bridge and Tappan Zee Bridge are presented where long pipe piles were successfully strain instrumented and load tested with the Statnamic (Rapid) load test method.
Experiences with Base Grouted Drilled Shafts in the Southeastern United States
Dapp, Steven. Muchard, Michael. Brown, Dan.
The use of base grouting (tip grouting) to enhance the axial capacity of drilled shaft foundations can achieve improvements in economy and reliability for many types of projects and soil profiles. Recent experiences on a range of different construction projects in the Southeastern U.S. illustrate the most attractive opportunities for utilizing this technique and some limitations of the method. The quality assurance provided by measurements obtained during post grouting the pile toe is another important aspect favoring its use; the base grouting is shown to identify weaker piles and provide a means of remediating some deficiencies so that increased foundation reliability is achieved. This paper provides an overview of the methods used to evaluate and design for base grouted shafts along with lessons learned from several case histories.