Tag Archives: Foundation Construction

TRB paper by andy boeckmann and erik loehr on Thermal requirements for drilled shafts

Andy Boeckmann, Ph.D., P.E. (DBA Senior Engineer) and Erik Loehr, Ph.D., P.E. (DBA Senior Principal Engineer) have published a paper on the topic of thermal testing of drilled shafts in the Transportation Research Board (TRB) journal Transportation Research Record.  Their co-author was  Zakaria El-tayash of Burns & McDonnell. 

As the drilled shaft diameters have increased in size over the years, designers and owners have had questions or concerns about the issues of temperature impacts to concrete durability similar to the issues with mass concrete placement for large structural elements.   Some transportation agencies have recently applied mass concrete provisions to drilled shafts, such as limits on maximum temperatures and maximum temperature differentials.  The temperatures commonly observed in large diameter drilled shafts have been observed to cause delayed ettringite formation (DEF) and thermal cracking in above-ground concrete elements.  This has led to the practice of applying to drilled shafts the control provisions that are based on dated practices for above-ground concrete. However, the reinforcement and confinement (embedded in soil and/or rock below grade) unique to drilled shafts should provide resistance to thermal cracking and possibly other effects of mass concrete temperatures.

Conceptual illustration of crack development in early age concrete with time from internal restraint. Adapted from Bamforth (2018) with permission from CIRIA

 

The paper reviews current requirements of several state DOTs  for addressing DEF and thermal cracking, then establishes a rational procedure for design of drilled shafts for durability requirements in response to hydration temperatures.  DEF is addressed through maximum temperature differential limitations while thermal cracking is addressed through calculations that explicitly consider the thermo-mechanical response of concrete for predicted temperatures.  The recommended procedure includes a detailed five step evaluation process.   Additional alternate steps for mitigation techniques and/or monitoring temperature are detailed as well.   The procedures allow for explicit account of project-specific characteristics, including ground conditions, concrete mix design characteristics, drilled shaft geometry, and the quantity of steel reinforcement.

 

Temperature differential between center and edge of shaft versus time from thermal model and from temperature measurements

 

The methodology was developed from guidance established by ACI and CIRIA and provides a rational means for designing drilled shafts for durability without imposing unnecessary constraints that may exacerbate challenges with effective construction of drilled shafts.  Results from application of the procedure indicate consideration of DEF and thermal cracking potential for drilled shafts is prudent, but provisions that have been applied to date are overly restrictive in many circumstances, particularly the commonly adopted 35 ?F maximum temperature differential provision.

You can get the paper from The Transportation Research Record at the link below.

Boeckmann, A.Z., El-tayash, Z., and Loehr, J.E. (2021). “Establishing and Satsifying Thermal Requirements for Drilled Shaft Concrete Based on Durability Considerations”, Transportation Research Record, March 2021.

Instrumentation at US 231 bridge and Slide

(Written by Andy Boeckmann – DBA)

After successful design and construction of the US 231 emergency slide repair in Lacey’s Spring, Alabama, DBA shifted gears to install a state-of-the-art monitoring system for the project. The monitoring system allows DBA and ALDOT to remotely detect any movement of the drilled shafts, changes in groundwater levels, and movement of the slope, itself.

The monitoring system includes ShapeAccelArray (SAAV) devices to measure displacement profiles with depth. SAAVs, which are manufactured by Measurand, consist of a chain of rigid segments, each 1.5-ft long and about 1-inch diameter. DBA installed 27 SAAV devices at US 231. Each of the 24 drilled shafts has one SAAV, which DBA installed in a 1-inch conduit welded to the drilled shaft reinforcement and emerging from the top of the grade beams connecting the shafts. The other three SAAVs are “free-field” SAAVs, installed in the soil between bridge bents. DBA worked with ALDOT’s drill crews to install the free-field SAAVs.

ALODT drill crew installing a free-field SAAV under the Northbound bridge.

 

Completed free-field and foundation instruments at Bent NB4.

 

DBA also worked with the ALDOT drill crews to install vibrating wire piezometer devices at six locations across the site. Each location includes two piezometers, one in the soil and one just below the top of rock. The piezometers were installed using the fully-grouted method. The piezometers measure pore pressure, which DBA uses to interpret groundwater conditions at the site.

 

Datalogger atop a vibrating wire piezometer.

 

All of the instruments are connected wirelessly to two central hubs that collect the data. The hubs are solar powered.  One of the hubs is equipped with a cellular modem that facilitates remote collection of the data.  RST Instruments manufactures the monitoring equipment as well as the vibrating wire piezometers.

Housing for SAAV devices installed in drilled shafts.

 

R-star hub and solar panel mounted to SB Bent 6.

 

Inside of data collection hub.

 

Results of the monitoring program indicate the foundation system is performing as designed. The US 231 structure has passed its first wet season with flying colors. Despite several periods of heavy rain that resulted in localized slope movement, the drilled shafts have shown only very small movement, typically less than 0.05 inch. The movement shown in the shafts indicates they are resisting loading from the slope movement, but with plenty of reserve capacity. The monitoring system has successfully captured realistic results from all instruments, including the drilled shaft and free-field SAAVs and piezometers.

Piezometer data shows strong correlation between rainfall and increases in groundwater levels.
Example of SAAV drilled shaft displacement. Shaft displacements are very small, typically less than the stated accuracy of the SAAV devices.

The monitoring system is more than just bells and whistles: it is an integral part of DBA’s design philosophy for the US 231 project. DBA engineers were able to implement the innovative strategy of drilled shafts through an active landslide because we knew performance of the foundation system would be actively monitored. This strategy represents a modern take on the observational method, which has represented best geotechnical engineering practice since the profession originated. DBA will also use results of the monitoring program to inform future designs, consistent with our commitment to using state of the art to improve the state of practice.

To read more in detail about the design and construction of the bridge foundations, we published an article i nthe April 2021 issue of Foundation Drilling Magazine:

Thompson, W.R. and Dapp, S.D. (2021). “Innovative Landslide Solution”, Foundation Drilling, Vol XLII, No. 3April 2021, pp51-62.

DBA Project Highlight: MoDOT I-44 Project Bridge Rebuild

I-44 Construction Aerial View; video courtesy of Emery Sapp & Sons

DBA has partnered with bridge designer Parsons and prime contractor Emery Sapp & Sons on a design/build project in Southwest Missouri being administered by MoDOT.  Design is complete and the project is in construction phase.  The project involves replacing 13 bridges and rehabilitating another six bridges along a 30-mile stretch of I-44 between Sarcoxie and Halltown.  The $36 million project is progressing nicely with construction beginning in 2019 and on schedule to be completed by December 15, 2021. To get a birds-eye view of some of the work, check out the video at the top of the post (from Emery Sapp & Sons)

Although smaller bridges than DBA typically works on, challenging subsurface conditions and unique structure types have made things interesting with respect to foundation design and construction.  Foundation types for various structures include driven H-piles installed with high-strain dynamic testing, drilled shafts with rock sockets in various rock formations, and spread footings bearing on near surface bedrock where applicable.  Pinnacle bedrock surface and karstic foundation conditions are prevalent in the area and this project is no exception.  Foundation design had to anticipate the complex subsurface conditions and consider constructability throughout the entire design process.

More information on the project can be found at MoDOT’s project page:  https://www.modot.org/i-44-project-bridge-rebuild .  Below are some photos taken by DBA staff while on site.

Photo Credit: DBA

 

Goethals Bridge – Up and out of the ground

(Post and photos provided by John Turner, Ph.D., P.E., D.GE of DBA.)

DBA has had the privilege to be the geotechnical/foundation engineer for the Goethals Bridge Replacement (GBR)Project, a design-build project for the Port Authority of New York & New Jersey (PANYNJ). The project will replace the existing Goethals Bridge that was built in the 1920s and carries I-278 over the Arthur Kill River between Elizabeth, New Jersey and Staten Island, New York.

Construction of drilled shafts continues as the superstructure begins to emerge over the skyline between Elizabeth, NJ and Staten Island, NY.  The new bridge will be a dual-span 1,983-ft long cable-stayed bridge with approach spans of over 2,500 ft on each side.  The bridge is supported on over 200 drilled shaft foundations ranging in diameter from 4.5 ft to 10 ft and socketed into Passaic Formation siltstone.

Goethals April 2016

The GBR is a Public-Private Partnership (P3) that represents a major milestone for the PANYNJ in its distinguished history of bridge building in the greater New York City metropolitan area.  The existing Goethals Bridge along with the Outerbridge Crossing and the Bayonne Bridge comprise the three Port Authority bridges connecting Staten Island with New Jersey.  The Goethals Bridge and the Outerbridge Crossing are cantilever truss structures and both opened on the same day in 1928. They were designed by J.A.L. Waddell under the supervision of the eminent engineer Othmar H. Ammann (1879-1965), who was the designer of many other iconic bridges in the NY City area including the Bayonne Bridge (1931), the George Washington Bridge (1931), and the Verrazano Narrows Bridge (1964).  The designer of record for the replacement Goethals Bridge is Parsons Corporation, which is the successor firm of Robinson & Steinman, whose principal David B. Steinman was also a notable NY area bridge designer and a contemporary and rival of O.H. Ammann.

Each main pylon tower of the GBR is supported on a group of six 9-ft diameter drilled shafts and each anchor pier is supported by two 10-ft diameter shafts.  Approach piers are two-column bents with each column supported on a rock-socketed drilled shaft.

Goethals shaft 1

DBA is the foundation design engineer of record and this project provides an example of how rock-socketed drilled shafts can provide a reliable and cost-effective means of supporting a major bridge by taking advantage of the high resistances that can be achieved.  Key factors involved in taking advantage of rock sockets for this project were:  (1) load testing to demonstrate high axial resistances (>30 ksf side resistance and  >300 ksf base resistance), (2) utilization of all relevant construction QC/QA tools to ensure that rock sockets are constructed in a manner that is consistent with construction of the load-tested shafts that provide the basis of the design, (3) close collaboration between all members of the design-build team, and (4) adequate subsurface characterization, especially a thorough characterization of rock characteristics and their effect on socket resistances. Load testing for this project demonstrates that side and base resistances can be used in combination to design rock socketed shafts for axial loading.  This approach avoids the use of unnecessarily deep sockets, thereby minimizing the associated construction risks and costs.

Goethals rendering

The GBR project developer is NYNJ Link Developer, LLC and construction is being performed by a joint venture of Kiewit-Weeks-Massman (KWM).  Parsons is the lead designer.  A construction web-cam and additional information on the GBR can be found at the Port Authority’s website: http://www.panynj.gov/bridges-tunnels/goethals-bridge-replacement.html

NCHRP Synthesis 478 – Design and Load Testing of Large Diameter Open-Ended Driven Piles

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The Transportation Research Board (TRB) has released a synthesis report prepared by Dan and Robert on large diameter piles: NCHRP Synthesis 478, Design and Load Testing of Large Diameter Open-Ended Driven Piles.  The report is a summary of the state of practice with regard to Large Diameter Open-Ended Piles (LDOEPs) in the transportation industry.  We conducted a survey of state DOTs as well as interviews with private practitioners to summarize current practices as well as recommend best practices with regard to the selection, design, installation, and testing of LDOEPs.   Several state DOTs are using LDOEPs more regularly where large foundation loads may exist and/or the piles are subject to significant unsupported length due to scour, liquefaction, or very weak surficial soils. Marine construction conditions also favor the use of these piles, particularly where pile bents might be employed to eliminate footings.

You can download a PDF of the report or purchase a hard copy at the link below.

Brown, D.A. and Thompson, W.R. (2015). NCHRP Synthesis 478, Design and Load Testing of Large Diameter Open-Ended Driven Piles, Transportation Research Board, National Academies, Washington, D.C.

Goethals Bridge Replacement – Webcam!

goethals-replacement-logo

DBA is on the design-build team that is replacing the Goethals Bridge for the Port Authority of New York and New Jersey (PANYNJ). We are not able to post much about the project or our involvement due to security agreements. However, the PANYNJ has a public website for the project (http://www.panynj.gov/bridges-tunnels/goethals-bridge-replacement.html) that has several webcams.  As is the case with most big projects these days, the webcams are a common feature and show some great views of the project.

To give you an idea of what the project involves, here is a summary from the PANYNJ site:

The replacement bridge will be located directly south of the existing bridge and will provide:

  • Three 12-foot-wide lanes in each direction replacing the current two narrow 10-foot-wide lanes
  • A 12-foot-wide outer shoulder and a 5-foot-wide inner shoulder in each direction
  • A 10-foot-wide sidewalk/bikeway along the northern edge of the New Jersey-bound roadway
  • Improved safety conditions and performance reliability by meeting current geometric design, structural integrity, security and seismic standards, and reduces life-cycle cost
  • A central corridor between the eastbound and westbound roadway decks, sufficient to accommodate potential transit service
  • State-of-the-art smart bridge technology

The project also includes the demolition of the existing bridge upon completion of the replacement bridge.

You can learn more about the project at the same web site.  There is also a site for the current bridge, including history of the construction, etc.

Leo Frigo Bridge–Repair Design

The Wisconsin DOT was set to request bids this week for repairs to the Leo Frigo Memorial Bridge on I-43 in Green Bay, with an anticipated start of construction on November 4th and reopening of the bridge on January 17th.  The repair will consist of using drilled shafts installed adjacent to the existing piers with a post-tensioned extension of the pile cap to transfer the loads to the shafts.  A schematic of the design from Wisconsin DOT (via Milwaukee Wisconsin Journal Sentinel)

Scot Becker, director of the Bureau of Structures and the state’s bridge engineer, said the fix will consist of installing four concrete shafts beneath five affected piers to take over support from corroded underground steel structures, called pilings. Then, the bridge itself will be jacked up 2 feet, and concrete and steel will be poured to keep the bridge in position.

The bridge, which spans the Fox River in Green Bay, has been closed since late September, after pilings became corroded and buckled under one of the piers, causing a 400-foot-long section of the bridge to sink 2 feet. Since then, it has drooped another half inch, and the state is monitoring the bridge for further movement.

An investigation concentrating mainly in the area from Quincy St. to the Fox River found that soil surrounding the pier contained industrial byproducts over wetlands, which caused the corrosion.

Temporary supports are already being installed by Lunda to shore up the sagging spans until the repairs can be completed.

The Green Bay Press Gazette has a page archiving all of their stories, videos, photos, etc. concerning this event.

http://media.jrn.com/images/LEOFRIG23GRevise.jpg

Happy Karl Terzaghi’s Birthday 2013!

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Happy Karl Terzaghi’s Birthday, my friends!  Yes, it is time to raise our coffee, espresso, tea, wine, beer or other beverage to toast the Father of Modern Soil Mechanics as has been our custom here at the DBA blog.

As I pondered what to write this year, I perused a couple of books and ended up looking through my copy of Richard Goodman’s  “Karl Terzaghi – The Engineer as Artist”.  Among the many stories and accounts, I found this passage recounting an incident in the late 1950s (Ch. 17, pp245):

At this critical time, the world was reminded of the terrible consequences of dam failure when Board member Andre Coyne’s Malpassat Dam failed in France, causing more than 400 deaths (in Frejus, very near Ruth’s 1939 refuge on the French Riviera).  It failed on the initial filling of the reservoir due to geological weakness in one of the rock abutments of the very thin concrete arch.Later Karl would express sever criticism of the decision to bold such a structure on a geologically inadequate site.  But now he comforted his distraught colleague, writing that “failures of this kind are, unfortunately, essential and inevitable links in the chain of progress in the realm of engineering, because there are no other means for detecting the limits to the validity of our concepts and procedures…. The torments which you experienced should at least be tempered by the knowledge that the sympathies of your colleagues in the engineering profession will be coupled with their gratitude for the benefits which they have derived from your bold pioneering.”

Throughout the book, Goodman does an excellent job of showing the different facets of Terzaghi, and this is no exception.  He had a reputation of being a tough, direct, and straight-forward engineer that did not pull punches.  Here we see a somewhat softer side as he comforts a colleague, who was an expert in his own right.

If you have not read Goodman’s book, I highly recommend it for all Terzaghi fans!  It is published by ASCE and can be found through the ASCE Bookstore, or at other book retailers.  (Disclosure:  Neither DBA or any of its employees receive any commissions, compensation, or other considerations for promoting this book.)

Call for Abstracts – 2015 International Foundations Congress and Equipment Exposition (IFCEE 2015)

IFCEE 2015 logo_150

Although 2015 seems like a long way away, when you are planning the largest foundation engineering and construction conference in the U.S., you need to get started early!  The organizing committee for the  the 2015 International Foundations Congress and Equipment Exposition (IFCEE 2015) has released the Call for Abstracts here at the conference website.

This conference will be at the JW Marriott in San Antonio, Texas, March 17-21, 2015 and is hosted by a joint effort of ADSC: The International Association of Foundation Drilling (ADSC), Deep Foundations Institute (DFI), Geo-Institute of the ASCE (G-I), and Pile Driving Contractors Association (PDCA).  The program will include technical paper sessions (as poster or podium presentations), panel discussions and debates, indoor exhibits, an outdoor equipment exposition, educational short courses, technical committee meetings, and networking events.

NCHRP Synthesis 429 – Geotechnical Information Practices in Design-Build Projects

nchrp_syn_429_cover

Early this year, NCHRP released a synthesis report on geotechnical practices related to design-build projects.  I have had writing a blog post on this on my “to do” list for a few months and finally got down the list!

NCHRP Synthesis 429 – Geotechnical Information Practices in Design-Build Projects is a report on the current practices of allocating and managing geotechnical risk through the use (or lack of!) geotechnical information in transportation project bid documents.  Even though design-build as a delivery process for projects has been around for a while now, the allocation of risk due to subsurface conditions is an issue still treated with a variety of approaches. 

Those of us who have been in this industry for a while know that a thorough geotechnical investigation reduces both cost risk and construction/schedule risk.  Design-build is an effective method for accelerating project construction and delivery; however, the acceleration of the schedule puts more pressure on the geotechnical design since “geotechnical investigation and design is usually the first design package that must be completed and geotechnical uncertainty is usually high at the time of DB contract award.”

Because geotechnical investigation and design is usually the first design package that must be completed and geotechnical uncertainty is usually high at the time of DB contract award, the design-builder’s geotechnical designers are under pressure to complete their work and enable foundation and other subsurface construction to commence. Successfully managing the geotechnical risk in a DB project is imperative to achieving the requisite level of quality in the finished product. The purpose of this synthesis is to benchmark the state of the practice regarding the use of geotechnical information in DB solicitation documents and contracts. The high level federal encouragement through EDC for state DOTs to accelerate project delivery by using DB elevates the need to manage geotechnical risk while expediting geotechnical design to a critical project success factor, and makes the results of this synthesis both timely and valuable.

As is the case with NCHRP synthesis reports, the authors conducted a literature review, conducted a survey of state DOTs and other agencies, and developed some conclusions that include effective practices for managing geotechnical risk.

The synthesis was based on a comprehensive literature review; a survey of U.S. DOTs, which received responses from 42 states (response rate = 84%); a content analysis of DB solicitation documents from 26 states; a content analysis of DB policy documents/guidelines from 12 state DOTs and 5 federal agencies; and interviews of 11 DB contractors whose markets encompass more than 30 states. The synthesis also furnishes three legal case studies (Colorado, Illinois, and Virginia) on cogent geotechnical issues and four geotechnical engineering case studies (Hawaii, Minnesota, Missouri, and Montana) that illustrate the methods transportation agencies use to deal with geotechnical issues on DB projects. Conclusions were drawn from the intersection of independent sources of information from the survey, case studies, and literature.

Some of the effective practices highlighted include the use of confidential Alternative Technical Concepts (ATC) during pre-bid, explicit differing site conditions (DSC) clauses that clearly quantify the design-build team’s risk and the threshold above which the DOT assumes the risk, the use of qualified personnel, and timely review schedules for geotechnical design items early in the project.

Our (DBA) experience in design-build has seen the range from effective practices to poor practices.  This report provides a great summary of many of the effective practices we have found to be beneficial and that help reduce conflicts and delays.  We can’t completely eliminate geotechnical risk, but it can be effectively and equitably managed.

Click on the link below to get a copy from NCHRP.

NCHRP Synthesis 429 – Geotechnical Information Practices in Design-Build Projects