Non-destructive Testing of Unknown Bridge Foundation Lengths Using Parallel Seismic Testing
Muchard, Michael; Savani, Chetan
DFI 45th Annual Conference, October 2020
The necessity to evaluate undocumented foundation lengths is essential in assessing the useable life, need for scour protection, retrofitting, or full reuse of existing bridge foundations. For this purpose, Parallel Seismic Testing (PST) has the best accuracy and applies to the widest range of foundation configurations used in bridge construction of any test method.
Although not limited to bridges, PST case studies are presented involving two bridges. To preface the case study discussions, an overview of the PST method is given along with its results and analysis thereof. In one of the cases, we were given the rare opportunity to see the existing piles being extracted long after the PST testing program was completed. The resulting Class A prediction reaffirms the accuracy of the method. The versatility of the PST method is also exemplified in the two cases presented, where unique situations from complex foundation systems were overcome by analysis to provide successful results.
Experiences with Base Grouted Drilled Shafts in Southern California
Muchard, Michael
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
Greis, John.
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.
ASCE 2015
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)
Muchard, Mike
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. ase 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.
DFI 2008
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.
Broadway Viaduct Design Phase Load Test Program for Post Grouted Shafts
Muchard, Michael. Farouz, Emad.
DFI 2008
A design phase load test program was performed at the Broadway Viaduct bridge site to evaluate load carrying capacity and constructability of post grouted drilled shafts. The program included construction, instrumentation, post grouting and load testing of three drilled shafts. Two shafts included sleeve port and plate base grouting apparatus and were post grouted. The third shaft was un-grouted and served as a control shaft for comparison of the un-grouted end bearing.
The Effect of Installation Technique on Capacity of Cylinder Piles in Yorktown Formation
Muchard, Michael. Palmer, Rick. Simpson, Michael.
ADSC/DFI 2009
Statnamic (Rapid) and dynamic tests were performed on seven (7) 54-inch spun-cast concrete cylinder piles installed with varying methods into the Yorktown Formation bearing stratum and the capacity measured. Four piles were part of an indicator pile program which was performed prior to installation of any production piles. Three additional Statnamic load tests were performed on production piles to assure capacity and verify final installation criteria. The pile design considered skin and tip resistance in the dominant geologic stratum for the Chesapeake Bay Area known as the “Yorktown Formation.” The upper surface of the Yorktown was encountered 30 to 50 feet in depth and extends to depths of 300 feet. It consists of medium dense to dense silty fine sand (SM) with abundant marine shell. It was moderately sensitive to elevated pore pressures from pile driving and was shown to regain most of its strength in about a week. Furthermore these soils were not conducive to plugging during driving or load testing. The tested cylinder piles were all 54-inch diameter, 6.5-inch wall with lengths of 160 to 164 feet. All of the test piles were cast with four levels of embedded strain gages to measure load transfer characteristics during Statnamic load testing. Statnamic load testing fully mobilized pile capacities ranging from 2,285 kips to 4,014 kips as a result of the various installation techniques. Dynamic testing consistently showed significantly lower pile capacity due to insufficient test energy of the hammer. An excessively rising soil and water column within the pile core during driving governed the need to predrill. However, the reduction in side shear resistance from predrilling ultimately required an additional 10 feet of pile penetration to obtain the required capacity. Furthermore, the end bearing appeared to act in an unplugged condition.
Recent Experiences with Concrete Cylinder Piles in Florida
Kemp, John. Muchard, Michael
ASCE 2009
Two case studies are presented where 1372 mm (54 inch) diameter concrete cylinder piles where used in recent bridge projects in Florida. The primary focus of the paper is on cracking and spalling of the piles during installation and the solutions used to overcome these problems. Field and laboratory test data are also presented which demonstrates some advantages of cylinder piles. The St. George Island Bridge in Apalachicola, Florida utilized segmented spun cast post-tensioned piles. Longitudinal cracking was found in 42 piles believed to be from excessive hoop stress induced by mud and water buildup within the pile during driving, commonly referred to as “water hammer”. The Trout River Bridge in Jacksonville, Florida utilized bed cast continuous prestressed piles. Severe spalling of the pile top during installation was encountered due to high localized stresses imparted by the driving hammer system. The cracking experienced on both projects proved to be a result of soil conditions and installation methods. Installation methods were modified to eliminate the cracking. These case studies should provide benefit to the engineering community in solving similar problems should they arise on other projects.
Statnamic Load Testing of Large Diameter Piles at Rigolets Pass Bridge Project
Robertson, Donald. Muchard, Michael
ASCE 2008
Statnamic load testing was performed on three 66 inch (1,676 mm) diameter, post tensioned, spun cast, concrete cylinder piles and one 30 inch (762 mm) square pre-stressed concrete pile as part of a construction phase load test program for the replacement of the US 90 over Rigolets Pass Bridge near Slidell, Louisiana. The test program also included dynamic testing on all piles and static load testing of the 30 inch (762 mm) pre-stressed concrete piling. Statnamic loads approaching 6,000 kips (27 MN) were utilized on the cylinder piles to fully mobilize side shear in these predominantly friction piles. The static load test and Statnamic load test results on the same 30 inch (762 mm) square pile showed excellent agreement in both load and displacement up to the point of the limiting applied static load. The signal match on this pile showed greater displacement at similar loads. The Statnamic tests of the cylinder piles showed ultimate static capacities of 2,966 kips (13.3 MN), 3,077 kips (13.7 MN) and 3,315 kips (14.7 MN). While the CAPWAP analysis of re-strikes on these piles showed ultimate static capacities of 1,245kips (5.5 MN), 2,030 kips (9.0 MN), and 2,116 kips (9.4 MN). These results suggest that the Statnamic test method was able to fully mobilize the pile side shear resistance.
Statnamic Load Testing of High Capacity Marine Foundations
Muchard, Michael
DFI 2006
STATNAMIC load testing augmented with embedded instrumentation has been successfully used to obtain structural and geotechnical design information on large diameter spun cast concrete cylinder piles on many large marine construction projects. The paper focuses on one particularly interesting large marine project involving a new bridge to St. George Island, Florida where instrumentation and STATNAMIC load testing was used in conjunction with static load testing on high capacity piles. The information presented includes embedded instrumentation measurements taken during pile fabrication (post-tensioning), during pile driving, during static load testing, and STATNAMIC load testing. As much of this data is the first of its kind on concrete cylinder piles, it is exciting to present the foundation industry with this additional insight as to the behavior of this pile type and the accuracy of the methods used to test them.
Integrity Evaluation of Driven Concrete Piles Utilizing Embedded Data Collectors
Robertson, Donald. Hecht, Kurt. Muchard, Michael
DFI 2012
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.
Foundation Investigation of Roger’s Bridge Low-Strain Integrity Testing & Parallel Seismic Testing Methods
Santee, Thomas. Simpson, Michael
Highway Geophysics NDE Conference 2008
Roger’s Bridge spans the Chattahoochee River approximately 25 miles northeast of downtown Atlanta, Georgia. Originally built sometime in the first half of the 1900’s it was apparently used for many years as a single lane bridge for vehicular traffic. Sometime in the 1960’s the bridge was abandoned. Recently, an interest in using the bridge again arose as part of a nature and bike trail initiative by the local metropolitan area. Prior to putting the bridge into use, rehabilitation of the bridge would be needed due to disrepair and neglect. Unfortunately, no bridge records existed and load carrying capabilities of the foundations were unknown. Therefore, non-destructive testing was selected by the project team in hopes of determining estimated lengths and depths of embedment for the foundation elements in the interior bents. The interior bent foundations consist of four concrete foundation elements (two in each interior bent). Each foundation element is circular with diameters of about 48 inches. All of the foundation elements extend above the ground 12 to 22 feet. All of the foundation elements have permanent steel casing (of approximately ¼ inch thickness) from at least some distance below the existing ground surface to the top of the foundation element. QORE Property Sciences3 performed a field exploration program near the interior bent foundations and installed PVC casings for parallel seismic testing. All four foundation elements were tested using the low-strain integrity test method. Two of the four foundation elements were tested using the parallel seismic method. Both test methods provided similar results, matched reasonably well with the available soil boring information, and proved helpful to the project designers.
Pier Pressure in Natchez, Mississippi: Post Grouted Drilled Shafts Pass Test
Muchard, Michael
ADSC Foundation Drilling Magazine 2004
A case history of post-grouted drilled shafts is presented as are application to the Natchez Trace bridge project in Natchez, Mississippi. Full article available as PDF.