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Purple Line Expansion project and Mill Creek Tunnel win awards from International Tunnelling Association

The International Tunnelling and Underground Space Association (ITA) announced the winners of its 2022 awards and American projects and engineers were represented in the international competition that is in its eighth year.

Organized by the ITA, the awards showcases the most ambitious underground projects all over the world as well as the latest innovations, techniques, and methods in tunneling.

Arnold Dix, President of the ITA, praised the quality of the award-winning projects, underlining that “The Tunneling Awards is a celebration of the great milestones and the great innovations achieved. It also highlights the contributions made to our planet and people. This year, 70 nominations from almost 20 countries have been considered by a panel of independently select judges. The ceremony today rewards the best in our industry, from the largest projects on earth right through to the latest innovations and productions. These amazing achievements can be enjoyed today.”

The Purple Line Expansion project in Los Angeles, CA was named the Major Project of the Year winner. This award is for projects with a budget of more than 500 million Euro ($530 million) The Skanska-Traylor-Shea Joint Venture (STS) is constructing the $1.9 billion design-build of the
Purple Line Extension, Section 1, in Los Angeles, CA. This is the first of three projects to extend the Purple Line from Wilshire/Western Station to Santa Monica, a tunnel project that has been in the works for more than 60 years.

This portion of the project will add 6.3 km (3.92 miles) to the Purple Line, beginning at the Wilshire/Western Station. The twin tunnel alignment travels beneath Wilshire Boulevard, and underground stations are under construction at Wilshire/La Brea, Wilshire/Fairfax, and Wilshire/La Cienega. The tunnels, mined by two Herrenknecht TBMs, are 10,287 m (35,750 linear ft) long with an inner diameter of 5.7 ft (18.8 ft).

The project also includes train control and signals, communications, traction power supply and distribution, and fare collection systems.

Technical Innovation of the Year was awarded for the “unprecedented in-tunnel diameter conversion of the largest hard rock TBM in the United States”

The largest hard rock tunnel boring machine (TBM) ever to bore in the United States, an 11.6 m (38 ft) diameter main beam TBM, recently underwent a planned in-tunnel diameter change to a more compact 9.9 m (32 ft). The first-of-its-kind conversion process for the main beam TBM was undertaken 2.8 km (1.7 mile) into the bore and was not done inside a shaft or pre-excavated portal.

The city of Dallas (project owner) originally designed 3 km (1.86 miles) of the downstream end of the Mill Creek Tunnel (8.2 km or 5.1 miles total tunnel length) to be a horseshoe shape (11.6 m x 9.9 m (38 ft x 32 ft) excavation), for the purpose of providing a larger capacity in this stretch, and to utilize only one size TBM for the entire tunnel excavation. The design called for a 9.9 m (32 ft) circular cross-section excavation, then utilizing a roadheader or conventional heavy civil equipment to bench the 3 km (1.86 mile) reach. In partnering with Robbins and Aldea Services, Southland Contracting was able to work with the owner and owner’s consultants to use a TBM that could excavate a larger diameter for the downstream end and be converted to the original 9.9 m (32 ft) diameter for the remaining 5.2 km (3.2 miles). Each entity played a key role in the successful completion of this TBM conversion. Robbins took on the challenge of designing a TBM at the larger diameter of 11.6 m, designed with skins and spacer segments that would work for both diameters, and could accommodate the constraints of the conversion process to the original diameter of 9.9 m (32 ft).

Young Tunneller of the Year

Erica Frederickson was named the Young Tunneller of the Year.

“Just two weeks after graduating from university in 2011, I started my career in the tunneling industry. I got my first taste of tunnels as a Field Engineer with Traylor Bros., Inc. on the NYC MTACC LIRR East Side Access Queens Bored Tunnels and Structures project,” Fredrickson wrote. “Looking back, I had no real idea of what to expect, other than I thought underground construction seemed “cool”. I did not expect to continue working for the same company and industry for 11 years, but there is something special about the tunneling industry that hooked me.

“Since that first job, I have worked on three more tunnel projects in three different cities across North America: the DC Water Blue Plains Tunnel in Washington, DC; the LACMTA Westside Purple Line Extension Section 1 in Los Angeles, CA; and the Second Narrows Water Supply Tunnel in Vancouver, BC. Each project has had its share of challenges, triumphs, stressed out moments, and opportunities for growth. But most of all, I remember each project for the friendships formed with my incredible colleagues who call tunneling their career, and for the reward of providing essential infrastructure that will improve the lives of millions for many years to come.”

  • Major Project of the year – Purple line extension – Los Angeles (USA)
  • Tunneling project of the year (50 – 500M€) – World’s first spiral excavation using H&V shield tunneling method (JAPAN)
  • Project of the year – Up To 50M€ including renovation – Guanyinyan tunnel – An urban tunnel project of the unequal span four-arch-tunnel with two-ways and 10-lanes (CHINA)
  • Technical innovation of the year – Unprecedented in-tunnel diameter conversion of the largest hard rock TBM in the USA
  • Beyond engineering – Multi pipe jacking method for the construction of city core metro station in soft soil strata (CHINA)
  • Product / equipment innovation of the year – Integration of robotics into the construction works of the Chuquicaamata underground mining site (CHILE)
  • Innovative underground space use – V-column space of Shenzen Huangmugang transportation hub (CHINA)
  • Young tunneller of the year – Erica Frederickson (USA)

The ITA Virtual Experience can be found at:

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