Chesapeake Bay Bridge-Tunnel photo
The structure through which the TBM pushed during breakout is known as a headwall, which is 5 ft. thick.
Cindy Riley – CEG Correspondent
The article below originally appeared in and is posted with permission from:
https://www.constructionequipmentguide.com
Construction crews in Virginia continue making progress on the $756 million Chesapeake Bay Bridge-Tunnel (CBBT) expansion as they look ahead to a 2028 completion date. The project includes a new two-lane tunnel from the southernmost island under the Thimble Shoal Channel to the next island, providing a new pathway for drivers crossing the Chesapeake Bay.
Workers reached a significant milestone in January, as the tunnel boring machine (TBM) broke through the receiving pit on Two Island at Thimble Shoal Channel.
Chesapeake Bay Bridge-Tunnel photo
"The parallel tunnel is a key component of enhancing the safety and efficiency of this vital transportation link," said Fred Stant, CBBT Commission chairman. "It demonstrates the CBBT Commission's commitment to advancing infrastructure and ensuring the long-term sustainability of the Chesapeake Bay Bridge-Tunnel."
With completion of the mining/boring of the new two-lane tunnel, the Chesapeake Tunnel Joint Venture (CTJV) began finishing off the new tube. The team is composed of Dragados USA and Schiavone Construction Company LLC.
During any tunnel construction project, the biggest risk is encountering unexpected obstacles underground. Crews don't have to be concerned at this point, but that wasn't always the case.
In May 2023, "Chessie" (the TBM) struck a large ship's anchor. The anchor was manufactured in England at the turn of the 20th century. It took crews an additional 10 months of construction to safely remove the obstruction and repair damage to the TBM. Tunneling resumed a year later, averaging 50 ft. per day.
The structure through which the TBM pushed during breakout is known as a headwall, which is 5 ft. thick. It took the TBM several hours to chew through the concrete making up the headwall. Additionally, the reinforcing material used at the location of the breakout is glass-fiber-reinforced plastic, which is used so the TBM can push through without risking serious damage during the breakout.
Temporary bracing struts and steel beams were used to provide additional support to the headwall of the receiving pit. Once the TBM made the initial breakthrough, these were removed to allow the TBM to complete its exit. This, in addition to the removal of the breakthrough debris, was completed in less than 48 hours.
Jeff Holland, executive director of the CBBT, noted the breakthrough was the culmination of extensive planning, engineering precision and complex construction work during the planned and unplanned phases of the tunnel mining.
"We especially commend the work crews who operated in a high-risk environment to remove the anchor obstruction without injury or loss of life. This engineering achievement marks a major step forward in enhancing the safety, connectivity and infrastructure for the many travelers who rely on the CBBT."
The new tunnel will feature safety features such as heat detection elements, a suppression system and fans to clear out smoke in case of fire. It also will have a full-length egress corridor that provides maintenance access and a place of refuge should a blaze occur.
Logistics is the biggest concern that remains on the project. A temporary work inhibitor is the TBM as it is disassembled and hauled off, because it blocks access from the north. The tunnel drainage system, which sits below the future roadway, also presents difficulties for tunnel access until the portal pump rooms at each end are built. The project location, at the mouth of the Chesapeake Bay and 4 mi. from shore, also can be challenging for crews.
The TBM and its various support systems are being removed. Roller compacted concrete is being placed in the bottom of the tunnel as ballast/fill and as support for the future roadway. Concrete wall pours in the new tunnel open approaches also are under way.
Key tasks remaining include construction of the roadway inside the tunnel, electrical and mechanical systems that will be used to operate the tunnel and construction of tunnel support buildings that will include the equipment to control the tunnel's electrical systems, pumping systems and ventilation.
In building the roadway inside the tunnel, once the ballast placement is complete, it will be possible to install the concrete roadway slab and the egress corridor. The lighting and the mechanical/plumbing elements of the tunnel will be installed during and after roadway construction.
Chesapeake Bay Bridge-Tunnel photo
When finished, the new tunnel will carry two new lanes of southbound traffic, and the existing tunnel will have two lanes of northbound traffic. John Hellman, project executive of Dragados USA, said completing the mile-long tunnel drive was a turning point for this monumental undertaking.
"This new tunnel will help provide a less congested and safer driving experience for commuters headed between Virginia Beach and Virginia's Eastern Shore. Congratulations to everyone involved in this incredible project." CEG
Cindy Riley
Birmingham, Ala., native Cindy RIley originally planned on a career in law, but during her sophomore year in college realized journalism was her true calling. A magna cum laude graduate of Samford University, Riley first worked in radio and TV. Named Best News Anchor, Best News Reporter and Best Investigative Reporter by the Associated Press, she interviewed numerous personalities, ranging from Dr. Henry Kissinger and President Bush to Michael Jordan and Captain Kangaroo.
As a print journalist, Riley has covered a variety of topics, including construction, business, health and the arts. In addition to CEG, her work has appeared in special reports for USA Today and the L.A. Times. Other publications have included New South Magazine, Portico, Thicket, Alabama Heritage, B-Metro, Business First and Birmingham Business Journal.
