Tag Archives: ALDOT

US 231 Emergency Slide Repair – Laceys Spring, Alabama

DBA has the great fortune to be working with the Alabama Department of Transportation (ALDOT) on a very interesting bridge project in Lacey’s Spring, Alabama just south of Huntsville, Alabama.  On February 12 and 13, 2020 a large landslide occurred on SR-53 (US-231) at milepost 301.7 in Morgan County approximately 1.7 miles south of the Laceys Spring Community.  The slide completely severed the 4-lane divided highway which is a major commuting route between Huntsville and several communities south of the city.  Many of the workers at the U.S. Army Redstone Arsenal, NASA Marshall Space Flight Center, and the contractors and vendors that support these two major installations live in the communities impacted by the closure of the highway.  Detours were established on existing state and county roads, but these added 30 to 60 minutes to commute times, depending on time of day.  ALDOT was under significant pressure from the impacted communities to quickly solve the problem and reopen the road.

ALDOT drill rigs performing exploratory drilling (DBA)

 

ALDOT drilling crews were immediately mobilized to the site to begin drilling exploratory borings and install slope inclinometer casings for monitoring slide movements.  The Department of Civil Engineering at Auburn University was engaged to perform geophysical testing in conjunction with an existing research project for ALDOT.  Geotechnical engineering firm TTL also assisted with field investigation efforts. 

DBA and ALDOT immediately began evaluating several alternate concepts for stabilizing the slide and reopening the road during the soil and rock exploratory drilling.  The design team looked at several retaining wall options, a complete rebuild of the roadway, and bridges.  ALDOT selected a solution that removed most of the existing roadway embankments (built in 1947 and 1970) to reduce loading on the slope and then spanning the slide area with bridges built on the existing road alignments, with the bridges designed to withstand future movements of the slope.  Excavation was begun by Reed Contracting before bridge design was complete in order for the rough grading to be done before the bridge contractor mobilized.

The bridges are two-lane structures, one Northbound and one Southbound, each about 947 ft in length.  The superstructure is AASHTO BT-72 concrete girders and a concrete deck.  There are seven spans in each bridge each about 135ft long.  The grading work was begun while the bridge was still being designed to accelerate the schedule and shorten the time the road would be closed.

The foundations for each pier are a pair of 9.5ft diameter, permanently cased drilled shafts with 9ft diameter rock sockets.  The sockets are 14ft long into the limestone and shale bedrock.  The limestone uniaxial compressive strengths range from 10,820 psi to 28,100 psi. 

After much design and analysis in a highly compressed schedule, a bridge contract was let for bid in early May 2020, less than 3 months after the slide occurred.  Brasfield & Gorrie was the successful bidder and awarded a $15 million contract that has incentives for finishing early, and disincentives for finishing late. 

 

ALDOT UAV flight June 16, 2020

ALDOT UAV flight July 07, 2020

ALDOT UAV flight July 23, 2020

ALDOT UAV flight July 28, 2020

ALDOT UAV Flight Aug 08, 2020

ALDOT UAV Flight Sep 2, 2020

ALDOT UAV Flight Sep 15, 2020

 

Excavating first shaft on the site (DBA)

 

A.H. Beck (Beck) is the drilled shaft contractor, drilling each shaft, placing reinforcement, and placing concrete.   The 9.5ft diameter permanent casing is 5/8 inch wall thickness spiral weld 60ksi steel fabricated by Nucor in Birmingham, Alabama.  The shafts are reinforced with a 1.5inch wall thickness, 8ft diameter, 60ksi steel pipe. These pipes were rolled and welded by Favor Steel in Birmingham, Alabama before being trucked to the site.  The steel plate was manufactured by SSAB in Axis, Alabama near Mobile.  So, the structural steel pipes were completely Alabama-made and the steel travel almost the length of the state!

8ft diameter x 1.5in wall steel pipe for shaft reinforcement (DBA)

 

Inner structural pipe (1.5in) and outer casing (5/8in) (DBA)

 

The pair of shafts for each pier is connected by a reinforced concrete grade beam 10ft wide by 7ft high by 46ft long. To connect the shafts to the grade beam, a 14ft long reinforcement cage is placed in each shaft, embedded 8ft into the shaft with 6ft embedded in the grade beam. The cage consists of 28 No.18 Grade 75 bars.

Grade beam at NB Bent 7 with column steel (DBA)

 

Completed shaft with reinforcing cage to embed in grade beam (DBA)

 

The project includes a robust instrumentation plan with ShapeArray inclinometers installed in each shaft and in the slope, supplemented by traditional inclinometers in the slope and vibrating piezometers to monitor groundwater levels.  DBA and ALDOT will monitor the bridge and slope, intending to be able to measure displacement and calculate strain and loads in the shafts should the slope move again in the future.

Foundations are scheduled to be completed by the end of July 2020.  The deadline to have the bridge open to traffic is early December, 2020, but Brasfield and Gorrie has an aggressive plan to complete the project early and earn the bonus for early completion.   Volkert is the CE&I Consultant on the project for ALDOT, providing construction management and inspection services for the project.

Click HERE for some of the photos DBA team members have taken during construction.

To see aerial views from ALDOT’s UAV flight taken on July 10, 2020, click HERE.

 

 

Pre-Bid Load Testing for the Mobile River Bridge and Bayway Public Private Partnership (P3) Project

DBA has been fortunate to be involved as a consult to Alabama Department of Transportation (ALDOT) for the  Mobile River Bridge and Bayway Project.  This project represents Alabama’s largest ever investment for a single infrastructure project.  The project includes a cable stayed bridge over the Mobile River and seven miles of bridge over Mobile Bay.  Bridge foundations therefore represent a major component of the estimated $2 billion project cost.  DBA serves as a foundation consultant under subcontract to Thompson Engineering, Inc..  Thompson is one of the ALDOT Advisory Team partners, the other partners being HDR and Mott MacDonald.

With the tremendous volume of foundations required for the project, the DBA/Thompson team worked with ALDOT’s Geotechnical Division to develop a pre-bid load test program to help reduce some of the risks that would face both ALDOT and prospective concessionaires.  Performing a deep foundation load test program during the procurement phase of a Public Private Partnership (P3) project can help the prospective concessionaires better define foundation design parameters and reduce uncertainties and risks related to constructability of the foundations.  The reduced risk leads to reduced costs by allowing the concessionaire to develop a more efficient design while minimizing contingency costs and potential delays related to foundation constructability or performance.

The load test program was designed to include the most likely foundation types that the prospective teams might use.  Several types of driven piles were installed and tested, including typical square and cylinder concrete piles used on the Alabama coast plus steel H-piles and an open-ended steel pipe pile.

All driven piles were subject to dynamic testing with a Pile Driving Analyzer during driving.  Restrikes with dynamic testing were conducted on all driven piles to evaluate potential strength gain with time.  Jetting techniques were specified for some piles to evaluate this installation technique which could potentially be used during construction.

Traditional axial static load tests were performed on steel HP14x89 and 18in Precast Prestressed Concrete (PPC) square piles.  Rapid (Statnamic) axial load tests were performed on 36 in PCC square piles, 54in PCC cylinder, and 60in steel open-end pipe piles.

A 72in diameter drilled shaft foundation was also installed and tested.  Axial load testing was done using a bi-directional load cell (AFT A-Cell).  Lateral load testing was done using the Statnamic device.

 

Here are some videos of the Statnamic testing, with slow motion action!

 

Foundation contractors that are part of a concessionaire team pursuing the project were allowed to bid the load test program.  Jordan Pile Driving was the successful bidder for the $3.7 million test project.  AFT provided the testing services for the project – dynamic, static, Statnamic, and A-Cell.

A summary of the results can be found in a presentation made to ALDOT at the 62nd Annual Alabama Transportation Conference on February 13, 2019.   (Click HERE to get the presentation). Publication of the results is anticipated to be made in the DFI Journal in the future.