By rosebell
A major landmark has been achieved in the Parallel Thimble Shoal Tunnel Project in the US state of Virginia, as Chesapeake Bay Bridge-Tunnel (CBBT) has announced.
Reaching the end destination, tunnel boring machine (TBM) Chessie with 13.1m diameter has successfully broke through the receiving pit on Two Island at Thimble Shoal Channel.
Following that the temporary bracing struts and steel beam are removed from the receiving wall, the 325ft-long TBM is due to complete the final phase of mining.
Linking two southbound trestles of the existing Chesapeake Bay Bridge-Tunnel, the $756m tunnel project involves constructing a 5,700ft bored tunnel, while this structure connects the Norfolk/Virginia Beach area to Virginia’s eastern shore.
According to CBBT Commission chairman Fred Stant: “The parallel tunnel is a key component of enhancing the safety and efficiency of this vital transportation link and demonstrates the CBBT Commission’s commitment to advancing infrastructure and ensuring the long-term sustainability of the Chesapeake Bay Bridge-Tunnel.”
The responsibility of designing and building tunnel boring machine for this project was up to Germany-based Herrenknecht.
TBM Chessie, which has a 43ft cutter head and a length of 308 ft, dug almost 500,000 cubic yards of soil and installed nearly 10,000 concrete segments, each weighing 10 tons.
As a partnership between Dragados USA and Schiavone Construction Company, Chesapeake Tunnel Joint Venture (CTJV) has the duty of design-build contractor for this project.
Both firms are part of Spain-based ACS Dragados, a global underground construction company, whereas ACS Dragados has been awarded over 550 underground projects and completed more than 940 miles of tunneling through various geological conditions.
The date of commencing mining for the two-lane, 1.6km long tunnel was February 2023 and in May 2023, Chessie encountered a large ship’s anchor, dating back to the early 1900s and manufactured in England.
While facing an eight-month delay for safe removal due to the obstruction, tunneling resumed in May last year, with progress averaging 15.2m daily.
CBBT executive director Jeff Holland said: “This breakthrough represents 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.”
Constructing the tunnel roadway, installing electrical and mechanical systems, and building support structures will be done by CTJV.
Upon completion, the new tunnel will carry southbound traffic, while the existing tunnel will handle northbound traffic.
Currently the scheduled date for completion of this project is early 2028.
