California High-Speed Train – Tule River Viaduct
By Jameson Schwab | December 7, 2022
DHC does not shy away from high profile projects, and in the state of California, High-Speed Rail is among the biggest and most anticipated projects the state has seen in decades. With the introduction of a high-speed rail system, the state could finally feel a little smaller, although construction of the rail has been riddled with roadblocks. When DHC was approached to bid for a portion of the temporary bridge falsework and formwork, we collectively decided to jump in and team up with Dragados-Flatiron Joint Venture (DFJV). The falsework we were bidding would span through the Thule River Viaduct, slated as California High-Speed Rail Authority’s Phase I construction of the new California High-Speed Train segment in Tulare County, CA. The proposed viaduct is approximately 3,500 ft long and we needed to design the falsework systems for DFJV to construct the pergola structure supporting the proposed concrete superstructure. Appropriately named, the roughly 30 ft tall “pergola” structure is made up of (24) 120 ft long spans that measures close to 1,600 ft along the viaduct. It crosses (3) BNSF rail tracks, a Caltrans and BNSF right-of-way, and it needed to allow adequate vertical and horizontal clearance to meet BNSF construction envelope requirements over the full length.
Our main goal with the falsework was to design systems that would be easy to erect and simple enough to inspect to minimize problems during construction. We faced the first challenge almost immediately: the sheer size of the viaduct. The majority of the falsework was designed to construct edge beams, solid 8 ft wide and 15 ft tall concrete beams running parallel with proposed high-speed rail alignment and straddling BNSF right-of-way to support the new box girder bridge along the pergola structure. We utilized 24” diameter steel pipes and up to W24 steel beams to form temporary bents throughout the alignment. The owner of the project, California High-Speed Rail Authority, posed another prominent challenge as we began to submit our designs. We quickly realized the review process was unlike any project we have seen, involving multiple 3rd party reviewers, various parties, and then a final review through Caltrans that was only accepted after all prior review was closed out. We worked closely with DFJV to form compromises with the reviewing agencies to keep the project moving in the right direction, a feat that was easier said than done.
Aside from overall size, the falsework needed to be designed around (3) separate alignments including edge beam supports and main bridge superstructure. We made every effort to work closely with DFJV to utilize familiar materials and construction methods to produce a design that DFJV’s labor crews could grow familiar with and repeat. The design also needed to withstand high winds in addition to certain levels of seismic activity to meet project specifications. The robust design helped our teams sleep easier at night knowing the falsework would remain standing even if extreme forces of nature were to pass through during the construction phase.
We completed the Tule River Edge Beam falsework and formwork design in June of 2021 and construction of the Tule River Viaduct is currently ongoing. The project is requiring DFJV’s crews to constantly move around, and DHC is here to help as new challenges arise. Other portions we partner with DFJV on vary from temporary trestle designs to allow worker access across Deer Creek, and formwork and temporary bracing for new reinforced concrete stem walls, retaining walls, and bridge deck slab structures at various site locations. DHC is looking forward to further working with DFJV to provide engineering support as construction progresses on the High-Speed Rail, as well as future projects to come.