Bridge Construction, Bridge Foundations, Foundation Testing, Micropiles

Lifting and Repairing the SR-67 Bridge in Elizabethton TN after Hurricane Helene

Pictures showing the bridge deck before (left) and after (right) the lifting operation. The Michels-DBA team lifted the bridge approximately 4.5-inches to restore its structural integrity

Post Authored by Adam Blazejowski, P.E. of DBA

In late September 2024, the State Route 67 bridge in Elizabethton, Tennessee was damaged during Hurricane Helene and rendered unsafe for public use. The large storm flow in the Doe River undermined the pier footings and caused the upstream side of the bridge to settle between 4 and 5 inches. The Tennessee Department of Transportation (TDOT) was under significant pressure from the impacted communities to reopen the bridge which averages more than 22,650 vehicles per day.  The team of Michels Construction Inc. (Michels) and Dan Brown and Associates (DBA) was engaged by TDOT to design and execute a repair solution to reopen the bridge on an accelerated timeline.

Michels used conventional and low-overhead micropile rigs working from the existing bridge deck as a working surface where practical to install the micropiles that were designed by DBA to lift and support the bridge

To bring the bridge back into service, the Michels-DBA team was tasked with carefully lifting the upstream side of the bridge approximately 4.5 inches and restoring the structural integrity of the impacted bridge pier. The team instrumented the approximately 100-year-old concrete arch span bridge with displacement and crack sensors to monitor the bridge stability during repair work. The repair solution involved de-watering under the bridge pier, installing Micropiles, shoring the bridge with steel frames connected to the micropiles, demolishing the existing footings, jacking the bridge, and constructing the pile cap.

DBA designed shoring frames to transfer load from the bridge deck beams directly to the micropile foundation to allow for demolition of the undermined footings.

After the bridge was shored, Michels demolished the undermined footings and installed the column frames that were designed by DBA to support the jacks underneath each column and transfer loads to the micropile foundation.

 

The bridge was successfully jacked back into place and the bridge was re-opened on July 2, about nine months after Hurricane Helene swept through East Tennessee. This successful design-build repair project demonstrates the intersection between geotechnical/structural engineering and the skilled construction process that brought the bridge back into service for the public.

The Michels-DBA team used a system of jacks to carefully lift the bridge underneath each column location. After the lifting operation was complete, Michels installed shim plates and removed the jacks to prepare for construction of the pile cap.

 

Ground Improvement, Sesimic and Earthquakes

Hybrid Ground Improvement System for Liquefaction and Settlement Mitigation

Malcolm Drilling, Inc. and Dan Brown and Associates, LLC were the design-build team for a hybrid ground improvement system consisting of vibro-stone columns (VSC) and cutter soil mixing (CSM) panel grids to mitigate liquefaction and achieve target settlement performance criteria for a mixed-use development in Santa Cruz, California.

The development is being done by the Lincoln Property Company and consists of three separate 7-story buildings including 175 apartments and ground floor retail. The separate buildings provide public access from the street to the San Lorenzo River multiuse path. The project is an anchor for the City of Santa Cruz’s plan for revitalizing downtown with enhanced access to the river and increased density of affordable housing.

VSC were used on the interior of the site to densify granular soils while the CSM grids were designed to limit shear demand around the perimeter of the site where existing sensitive buildings and a USACE-controlled levee along the San Lorenzo River prevented the use of vibratory methods. The final project included 125 CSM panels for ground improvement and 558 VSC.

VSC probe and aggregate hopper supported by crane (foreground) with CFA piling rig on standby to predrill through refusal layers. San Lorenzo River levee visible in background
Cutter soil mix rig installing panel adjacent to existing structure at south site perimeter.

The hybrid ground improvement system supported a mat foundation beneath a single-level basement that spanned the entire site, atop which three individual seven-story mixed-use structures were constructed. The grade-level diaphragm resulted in combined seismic participation from the three structures which led to significant mat bearing pressures beneath shear walls and at the site perimeter.

In true design-build fashion, final geotechnical information was not available until after construction began and existing buildings on the site were demolished. This allowed access to install trial patterns of VSC with pre- and post-installation testing as well as additional exploratory CPT to identify the depth transition for the Purisma Formation bearing layer from about 60 ft in the northern portion of the site to about 20 ft in the southern portion of the site. VSC and CSM panel depths through the transition zone finalized while construction of the first production CSM panels was underway at the southern site edge.

Along with the Owner’s geotechnical engineer, Rockridge Geotechnical, DBA and Malcolm implemented multiple quality assurance and control measures. The CSM design and QA/QC program included a bench-scale study using soil samples from the geotechnical investigation, test panel installation using three different binder mixes with variable cement content to investigate soil mix compressive strengths, daily wet-grab sampling of production columns for strength testing, and coring of select columns for visual observation of mix continuity and sampling for strength testing of cured in-situ soil mix. Ground improvement through VSC was verified using post-installation CPT which were analyzed and evaluated on an individual basis against project performance criteria.

CSM core samples.
Pre- and post-VSC installation CPT profiles for liquefaction triggering.

The RiverRow project demonstrates the successful use of the design-build method to optimize site-specific ground improvement technologies to meet multiple project needs while safeguarding the interest of a wide variety of surrounding stakeholders, including sensitive structures and a USACE-controlled levee.

 
Foundation Design, Industry News and Events, Terzaghi & History

Happy Karl Terzaghi’s Birthday 2024

Happy Karl Terzaghi’s Birthday!  Yes, today is the 141st anniversary of the birth of the man considered The Father of Modern Soil Mechanics!

It has been a couple of years since I have posted a Happy Terzaghi’s Birthday note.  Life – both inside and outside work – sometimes has a way of derailing us from established routines, patterns, and our “usual things”.  I told myself this year would be different, so here I am!  Some of you have been on my list for a few years, some of you may be new.  You are always welcome to ask me to drop you, or to forward to others!

When thinking about what to write, I looked through several things on my bookshelf and ended up reading the Preface to “Soil Mechanics in Engineering Practice”, Terzaghi and Peck (1948).  I am sure I read this years ago when a friend gave me this book as a gift, but today it jumped out for me to use here.  Professors Terzaghi and Peck are “setting up” how they organized the book, with the “heart of the book” being the part that deals with the art of getting results in practice.  This paragraph sets it up beautifully, starting with a lament that the increase in research has started to digress the profession away from the practical towards the few areas that can be precisely measured or understood (and this was in 1948!).

“Unfortunately, the research activities in soil mechanics had one undesirable psychological effect.  They diverted the attention of many investigators and teachers from the manifold limitations imposed by nature on the application of mathematics to problems in earthwork engineering.  As a consequence, more and more emphasis has been placed on refinements in sampling and testing and on those very few problems that can be solved with accuracy.  Yet, accurate solutions can be obtained only if the soil strata are practically homogenous and continuous in horizontal directions.  Furthermore, since the investigations leading to accurate solutions involve highly specialized methods of sampling and testing, they are justified only in exceptional cases.  On the overwhelming majority of jobs no more than an approximate forecast is needed, and if such a forecast cannot be made by simple means it cannot be made at all.  If it is not possible to make an approximate forecast, the behavior of the soil must be observed during construction, and the design may subsequently have to be modified in accordance with the findings.  These facts cannot be ignored without defying the purpose of soil mechanics. “

How true at times this is still today!  Our high-tech world sometimes leads us into the trap that the answer is better the more precise we can be in our capture, measurement, analysis, and calculations.  However, simple is many times still as precise as we need and we must be able to know when that is the case, and how to convey it to others.  We also need to know how to back-check our complex models with a simplified hand calculation or “eye ball” judgment.

So, raise that mug of coffee, cup of tea, can of Red Bull, or favorite after-hours beverage (when it is after hours!) to the timeless words from two of the “founding fathers” of geotechnical engineering and practice.  Have a great Karl Terzaghi’s Birthday!

DBA News, Research, Slope Stability

DFI Publishes Landslide Stabilization and Excavation Support Report

The Deep Foundations Institute (DFI) has just published a new report entitled “Guidance for Factoring Deep Foundation Structural Resistance for Landslide Stabilization and Excavation Support“, Final Report, CPF-2017-LAND-1 .  The authors are our very own Ben Turner, Dan Ding, Erik Loehr, and Paul Axtell.

To borrow from the authors’ introduction:

This report provides guidance for factoring deep foundation passive structural resistance for use in two-dimensional limit-equilibrium SSA, and is intended to serve as a consensus document on this subject. The report is divided into two main sections. The first section provides an overview of the basic framework for incorporating deep foundation elements into global stability analyses, followed by a discussion of the different possible methods for factoring (or not) structural resistance at different stages of the analysis. From this discussion, various plausible combinations of methods for including or not including load and resistance factors are identified, including a simple example.  In the second section of the report, the various factoring methods are applied to three case studies in order to analyze the influence of factoring method on reliability. The report concludes with a summary of the recommended approach for incorporating deep foundation resistance in SSA, informed by the conclusions presented in the earlier sections.

The report can be downloaded for free from DFI at the Committee Project Fund page (https://www.dfi.org/cpf) . Scroll down and look for the Landslides and Slope Stabilization Committee.    The DFI committees fund a lot of projects that result in reports such as this that benefit our industry and the state of practice.

 

While the report is free, you can access so much more, including the DFI Journal, by becoming a member.

Bridge Foundations, Foundation Design, Foundation Testing, Industry News and Events

FHWA GEC 15 (Foundation Acceptance) Now Published

FHWA has published (posted the PDF!) of Geotechnical Engineering Circular 015 – Acceptance Procedures for Structural Foundations of Transportation Structures.   Work began on this in 2019 and was delayed due to COVID.   Andy Boeckmann, Dan Brown, Erik Loehr, and John Turner of DBA are the authors.  They worked hard with Silas Nichols and the team at FHWA to produce a great guidance document for accepting deep foundations supporting transportation structures.  Here is a bit from the Introduction in Chapter 1 that gives the “big picture” of this GEC:

Foundation acceptance is a crucial component of the design and construction process used to develop transportation infrastructure in the United States today. As considered in this circular, foundation acceptance refers to a process resulting in approval of payment
to the constructor for installation of a deep foundation element. The process should involve the following actions by an owner agency, or entity acting on its behalf:


      1. Establishment of measurable and achievable acceptance criteria that serve as assurance that a foundation element will fulfill all appropriate performance requirements, and


       2. Documented evaluation of the constructed foundation element to demonstrate that the established acceptance criteria have been satisfied.


Foundation acceptance is the culmination of quality assurance (QA) efforts that, when appropriately implemented, provides the owner agency with confidence that a foundation element will fulfill all appropriate performance requirements. In some instances, the
foundation acceptance process may include provisions for cost adjustments for foundation elements that do not strictly satisfy established acceptance criteria, but that are nevertheless judged to satisfy all appropriate performance requirements and which
the owner agency agrees to accept.

Topics covered in this GEC include the framework for accepting deep foundations (project delivery, participants, role of QA/QC,etc.) , roles of inspection and testing, and specific items of concern for drilled shafts, driven piles, micropiles, and continuous flight auger piles.  You can download the PDF at the link below or on the FHWA Geotechnical Publications page HERE.

 

Acceptance Procedures for Structural Foundations of Transportation Structures  (FHWA-HIF-22-024, Geotechnical Engineering Circular 015).  Loehr, E.L., Brown, D.A., Turner, J.P., and Boeckmann, A.Z. (2022).

Micropiles, Research

NCHRP micropile study report published – NCHRP Report 989

At long last, the report for the NCHRP micropile study performed by Erik, Dan D., and Andy is published. The report, Reliability-Based Geotechnical Resistance Factors for Axially Loaded Micropiles, is the result of a considerable research effort that aims to rework AASHTO’s micropile design methods. Highlights of the research tasks are listed below.

 

  • Compile a database of micropile load tests and organize the database by micropile type and ground conditions.
  • Develop new presumptive and predictive models for micropile design. The presumptive models are based only on micropile type and ground condition; the predictive models further consider soil or rock strength.
  • Calibrate probabilistic resistance factors for micropile design based on presumptive and predictive models, and for designs based on site-specific load tests. If adopted, the resistance factors for designs based on load tests would be the first for AASHTO to be based on probabilistic calibration rather than fitting to historical practices.

 

The report can be downloaded for free from TRB’s website:

 

https://www.trb.org/Publications/Blurbs/182710.aspx

DBA News

Welcome Aaron Leopold, P.E.!

Aaron Leopold, P.E. joined the team this May with 8 years of geotechnical engineering experience.  He received a BS and MS in Civil Engineering from the University of Illinois at Urbana-Champaign.  His previous work at Shannon & Wilson mainly focused on the design and construction of deep foundations and retention systems.  Aaron was often on the road, observing complex geotechnical projects throughout the Midwest and Western United States consisting of drilled shafts, ground anchors, micropiles, augercast piles, and other deep foundation and earth retention systems.  He has supported numerous landslide stabilization projects utilizing his knowledge of 2D and 3D numerical modeling and has worked on large design-build projects from the pursuit through construction in the Rockies.  Aaron is also heavily involved within ASCE and other professional organizations in Colorado and will be based in Denver.

DBA News

Welcome Adam blazejowski and frank russell!

We are starting 2022 with two new faces at DBA – a big welcome to Adam Blazejowski, EI and Frank Russell, EI.  Both will be based in our office in Knoxville, Tennessee, but will soon be like the rest of us at DBA – traveling to interesting project sites all over the U.S.  They will be working on many of the deep foundation and earth retention projects that are our staples.

Adam is  from London, Canada where he completed his B.S. degree in civil engineering at Western University in 2020.  He came to the United States to complete an M.S. in geotechnical engineering at Virginia Tech, where he performed research on the cyclic strength of sands.  Adam is also interested in risk-based design and reliability in geotechnical engineering.

Frank  is from Hickory Flat, Georgia and graduated from Auburn University with his B.S. in 2019 and his M.S. in 2021 in civil engineering.  During graduate school, he was a recipient of the Long Family Endowed Civil Engineering Graduate Study Scholarship from the ADSC – The International Association of Foundation Drilling. His graduate school research evaluated the methods used in pile load testing across Alabama Department of Transportation projects. 

Bridge Construction, Bridge Foundations

DBA Helps MnDOT Manage Risk for Dam Site

DBA recently completed construction observation of pile driving and earthwork for TH-84 across Norway Brook in Pine River, MN. The structure may look like a run of the mill bridge, but the project was replete with geotechnical challenges associated with constructing a new bridge at the toe of an active dam. (We use “run of the mill” with all due affection; there’s no such thing as a boring bridge to DBA.)

During the design phase, DBA designed an instrumentation system and used the resulting piezometric information to calibrate seepage models for the site. The calibrated models were used to analyze conditions during and after construction of the new bridge. DBA also developed an emergency action plan (EAP) that established items to observe during construction, defined levels of distress leading up to all potential failure mechanisms, and designated response actions associated with the distress levels. During construction, DBA was on-site to implement the EAP, coordinating with the contractor, Schroeder Construction, Inc., and MnDOT to quickly respond to any evidence of distress.

Throughout analysis, EAP development, and EAP implementation, DBA collaborated with the bridge designer, Parsons, and MnDOT to identify, explain, and manage the risks associated with this unique and challenging project. We are pleased to see live traffic crossing the dam in the picturesque Minnesota North Country!

Here is a link to a video shot by Dan Ding of DBA during construction:

Finally, some photos of the finished bridge:

 

Bridge Construction, Bridge Foundations, Drilled Shafts, Foundation Design, Sesimic and Earthquakes

PROJECT HIGHLIGHT: 30 CROSSING DESIGN-BUILD

DBA is pleased to be part of the Kiewit Massman Construction (KMC) design-build team delivering the first transportation design-build project in the State of Arkansas, 30 Crossing. The project will improve traffic patterns and capacity along a 3-mile urban corridor of Interstate 30 from the Interstate 630 interchange south of downtown Little Rock to the Interstate 40 interchange in North Little Rock. The project includes replacing the existing bridge over the Arkansas River with two bridges supporting 12 lanes of traffic. 30 Crossing is the capstone project of the Connecting Arkansas Program (CAP), one of the largest highway improvement programs ever undertaken by the Arkansas Department of Transportation (ArDOT).

Teamed with designers Burns & McDonnell and HDR, DBA is the lead geotechnical and foundation designer for the navigation unit and north approach unit of the new river bridges. The bridge foundations are 10-ft diameter drilled shafts socketed into shale bedrock. Due to the project’s proximity to the New Madrid Seismic zone, design of the bridges included seismic considerations for critical operational class structures. Geotechnical seismic analysis included liquefaction triggering and lateral spreading evaluation. DBA worked closely with the structural designers to consider kinematic loads induced by lateral spreading and the interaction of substructure and superstructure components during lateral spreading events. The north abutment includes a column supported MSE wall embankment (CSE). The CSE ground improvement is included to mitigate performance and stability issues associated with shallow, soft alluvial silts and liquefaction hazards associated with deeper, alluvial sands.

KMC is self-performing the drilled shaft construction and CSE installation. To date, all of the eastbound bridge drilled shafts have been installed in the river and for the north approach. The ground improvement elements as part of the CSE beneath the eastbound embankment has also been completed. Once the eastbound bridge is ready for traffic in 2022, both directions of Interstate 30 will be temporarily shifted to the eastbound bridge, and the existing bridge will be demolished to allow for construction of the westbound bridge in its place.

Senior Engineer, David Graham, P.E., is the geotechnical engineer of record and has been involved in all aspects of the project form pursuit phase to current construction activities with significant contribution and guidance of Senior Principal Engineer and COO, Paul Axtell, P.E., D.GE. Senior Engineer, Ben Turner, Ph.D., P.E., G.E., lead the geotechnical seismic design and analysis effort. Project Engineers, Dan Ding, Ph.D., P.E. and Nathan Glinski, P.E., continue to be heavily involved in construction support and observation.

Eastbound Pier 13

Westbound Pier 13 drilled shafts

Looking north from Pier 13 at Eastbound Piers 14 and 15

Photos Credit: DBA

Specialists in Deep Foundation Design, Construction, and Testing and Slope Stability Problems