Tag Archives: rockfall

TH 53 Bridge Begins to Rise from the Ground

Bridge and Subsurface Rendering
Bridge and Subsurface Rendering (rendering courtesy of MnDOT)

A lot has changed from a year ago at the TH 53 Bridge sight near Virginia, Minnesota.  This time last year, the design-phase test pile program was wrapping up with three Statnamic load tests and we had just completed our initial geologic field investigation.  Since then, significant excavation, rockfall protection, and foundation work has been completed.  During summer and fall of 2015, DBA worked closely with contractors Hoover Construction and Pacific Blasting to maintain rockfall protection throughout the East Abutment and Pier 1 (East Pier) excavation process.  Official ground breaking occurred last November and foundation work started shortly after.  A total of 32, 30-in micropile foundations have been installed by Veit Specialty Contracting  and Kiewet Infrastructure  has completed a temporary causeway across the massive Rouchleau Pit by placing over 300,000 cubic yards of fill.

With the foundations of both piers complete, and the pier towers are starting to rise up, where they will carry the bridge deck 200 ft above.  The abutments are also taking shape with rock bearing concrete footings now poured on both sides of the pit.  The only foundation work left is to install tieback anchors at the East Abutment, which will reduce the lateral loading of the tall piers.

In a little over a year, the bridge is scheduled to open to traffic.  You can keep track of the progress through the project web cam.

Current View of Site, Piers Beginning to Rise
Current View of Site, Piers Beginning to Rise (photo from OxBlue Web Cam)

Ground Breaking of New TH 53 Bridge in Minnesota

TH 53 Bridge

TH 53 Bridge, artistic rendering courtesy of MnDOT

The official groundbreaking for the Trunk Highway (TH) 53 Bridge and Relocation Project occurred last week at the project site in Virginia, Minnesota.  The bridge, which is the main element of the project, will span the Rouchleau Iron Ore Mine Pit.  The project is scheduled to be completed in a brisk two years in order to allow for mining where a section of TH 53 is currently located.  Upon completion the 1,100-foot long bridge will be Minnesota’s highest, with the roadway sitting approximately 330 feet above the bottom of the floor of the Rouchleau Pit.  Kiewit was selected as the general contractor for the project with Veit Specialty Contracting as the foundation contractor.

Foundation construction will start in late November or early December with the installation of 30-inch diameter micropile foundations for the western pier of the three span, steel plate girder bridge.  Although the foundation work is just about to get started, DBA has been hard at work on the project for over a year.  DBA first got involved as a consultant to MnDOT for the design-phase load test program conducted last fall.  Since then, DBA was contracted as the geotechnical engineer of record for the project.  Working with bridge designer Parsons, DBA designed the bridge foundations, an anchored abutment, and rockfall hazard mitigation systems for this geologically challenging site.  DBA has also analyzed several soil and rock slopes to verify stability of the bridge and roadway.

Most recently, some of us were on site to inspect some of the rockfall protection elements on the east side of the mine pit. Last week we spent two days climbing and repelling a on a portion of the eastern highwall, which is currently covered in rockfall protection drapery. The drapery was installed for the protection of workers excavating rock for the eastern bridge pier.   The drapery was installed by Pacific Blasting in association with Hoover Construction.  Some pictures from our drapery inspection visit are below.

For more information about the project, click here, and for our previous blog posts on this project, click here.

John and Paul provide some scale to this picture as they work their way down the drapery.

 John concentrating as he inspects the drapery seam as he decends.

DBA Engineers Perform “Extreme” Geologic Investigation

DBA engineers prepare to go over the edge of the 200-ft tall west wall of the Rouchleau mine pit with the load test site in the background. From left to right: David Graham, Nathan Glinski, Ryan Turner, and Paul Axtell
DBA engineers prepare to go over the edge of the 200-ft tall west wall of the Rouchleau mine pit with the load test site in the background. From left to right: David Graham, Nathan Glinski, and Paul Axtell (far right).

DBA is currently working with structural designer Parsons to design what will be Minnesota’s tallest bridge.  The bridge will span the currently inactive Rouchleau open pit iron ore mine near Virginia, Minnesota. MnDOT is moving the alignment of the existing Hwy 53 to make way for future mining in the area.  DBA is the lead geotechnical designer on the project in addition to being contracted as MnDOT’s load test expert for the ongoing design phase load test program.

As part of our site investigation to gather information on rock fall and the site geology, five DBA engineers (John Turner, Paul Axtell, Tim Siegel, Nathan Glinksi, and David Graham) got up close and personal with the site by rappelling off the near vertical cut faces on either side of the Rouchleau pit! Traversing the over 200-ft tall cut faces of the nearly 2-billion year Biwabik Formation rock formation by rope and harness, we collected valuable geologic data.  We also took some great pictures like the ones posted to our Google Photos account.  In addition to the still pictures, we took some videos of a few rock fall tests, which are on our YouTube channel.

If you would like to know more about this interesting project on Minnesota’s Iron Range, you can check out our project summary sheet, visit MnDOT’s project page, or stay tuned to this blog for more updates.  There is also an online article about the project that was recently published by Civil Engineering Magazine.