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tuc &
The Official Publication of UCA of SME
//////////
///// ®
Tunneling & Underground Construction
www.TUCmagazine.com Volume 15 N0. 2 June 2021
Design for intersecting tunnels
Hybrid metro stations
RETC returns to in-person meeting
RETCShowGuide
Special Editorial Supplement from the publisher of Inside!
™
METRO LOS ANGELES, USA
SUCCESS STORY
IN CALIFORNIA
WITH 10 TBMS
120 million passengers are travelling through Los Angeles
every year. In the past 15 years a total of 10 EPB Shields
have been built for more than 35 km of new metro lines.
Herrenknecht guarantees the local support with their
office in Sumner, WA.
herrenknecht.com/MetroLA
Client:
Los Angeles Metropolitan Transportation Authority
Customer:
Purple Line Section 3 – Frontier-Kemper Constructors, Inc. /
Tutor Perini JV
Purple Line Section 2 – Frontier-Kemper Constructors, Inc.
Purple Line Section 1 – Skanska / Traylor / J.F. Shea JV
Regional Connector Transit Corridor - Regional Connector
Constructors (Skanska / Traylor JV)
Crenshaw/LAX Transit Corridor – Walsh / Shea Corridor
Constructors
Gold Line Eastside Extension – Traylor Bros., Inc.
tuc &
June Contents
Departments Cover Story
2
Chairman’s column In This Issue
The city of Charleston’s Spring/Fishburne US17 Drainage
Improvements Project is a five-phase program designed
4 to alleviate flooding in two drainage basins covering
Underground approximately 202 ha (500 acres), or about 20 percent
construction news of the Charleston peninsula. This project has several
objectives: to improve the mobility, efficiency, emergency
preparedness and community livability; and, most
importantly, to alleviate many of the flooding problems by
28 reinvesting in the infrastructure. See the article on page
UCA of SME News 16.
34
Tunnel demand
forecast Feature Articles
36 16
Classifieds Design and construction
considerations for intersecting
37 tunnels — Charleston, SC
RETC ShowGuide
Steve Kirk, Michael Miglioretti, Kyle
White, Lindsey Schneider, Jeffrey P.
Kolzow
22
Hybrid metro station for
mitigation of construction
disturbance
Oliver Martin
28
UCA returns to in-person meetings
with RETC in Las Vegas, NV
Margo Ellis
tucmagazine.com
AN OFFICIAL PUBLICATION OF UCA OF SME | WWW.SMENET.ORG | VOLUME 15 NO. 2 | JUNE 2021
Copyright 2021 by the Society for Mining, Metallurgy and Exploration, Inc. All rights reserved. TUNNELING & UNDERGROUND CON-
STRUCTION (ISSN 0026–5187) is published quarterly by the Society for Mining, Metallurgy, and Exploration, Inc., at 12999 E. Adam Aircraft Special editorial section
Circle, Englewood, CO 80112-4167. Phone 1-800-763-3132 or 303-973-9550. Fax: 303-973-3845 or e-mail: sme@smenet.org. Website: www.
smenet.org. POSTMASTER: Send changes of address to TUNNELING & UNDERGROUND CONSTRUCTION, 12999 E. Adam Aircraft
from the publisher of
Circle, Englewood, CO 80112-4167. Article copies and back issues available on microfilm or microfiche from Linda Hall Library in Kansas Mining Engineering
City, Mo. Printed by Publication Printers.
Reproduction: More than one photocopy of an item from SME may be made for internal use, provided fees are paid directly to the Copyright
Clearance Center, 27 Congress St., Salem, MA 01970, USA. Phone 978-750-8400, fax 978-750-4470. Any other form of reproduction requires special
permission from, and may be subject to fees by SME. SME is not responsible for any statements made or opinions expressed in its publications. ™
Member subscription rate included in dues.
Tunneling & Underground Construction June 2021 1
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Chairman’s Column
Looking back and looking ahead Editorial Staff
Editor
as term comes to an close William Gleason
gleason@smenet.org
T
his is my last column in this and for the UCA. This is something
magazine as the Chair of the I have seen help my own career Associate Editor
UCA Executive Committee, tremendously, so encouraging Margo Ellis
so it is somewhat inevitable for this participation is a particular passion ellis@smenet.org
column to have a look back and look of mine. We have worked as a group
forward. As the Chair of UCA, you at UCA to expand the number Production Graphic Artist
take on the role of a steward, building of volunteers and there are many Ted Robertson
on the achievements and leadership ongoing and new opportunities, such robertson@smenet.org
of those that have gone before and as:
trying to push forward some key Business Staff
objectives into the future. I hope • An increase in the number and Media Manager
to have left some fertile ground on quality of guideline publications Advertising
which future leadership can continue (e.g., we now have several in the Gary Garvey
to build. pipeline — risk management, garvey@smenet.org
Looking back, I said this in my TBM selection, alternative
first column two years ago: delivery, backfill grouting and Phone +1-800-763-3132 or +1-303-973-4200
In addition to continuing the others). Fax +1-303-973-3845
great work of the UCA, I have three • We have created a website
areas of focus for my two-year tenure and expanded the Down for Internet www.smenet.org
in the chair: That initiative to engage young
members and students, bringing Society for Mining, Metallurgy,
1. A focus on listening to what new blood into the industry. and Exploration, Inc. Officers
the industry needs and wants • We have expanded our outreach President
from the UCA and setting out a to colleges and even high schools,
William Edgerton
clear pathway of action items to encouraging presentations
achieve those goals. and preparing materials for
2. A focus on getting more presenters. President-Elect
volunteers engaged in UCA • We have encouraged and further Ronald Parratt
activities so we can achieve empowered the Young Members
our goals in a reasonable and and Women in Tunneling groups, Past President
practical timeframe. with conferences and other Robert Schafer
3. Provide clear and transparent events for networking and
feedback to the industry about advancement. Representation Executive Director
what the UCA is doing on behalf of UCA at the newly formed David L. Kanagy
of the members. SME Inclusion and Diversity
committee will drive our passion
After multiple member to increase the number and Underground Construction
engagement surveys and an industry influence of these important Association of SME
leadership survey ahead of the groups for the future of our Executive Committee
strategic planning exercise, it appears industry. Robert Goodfellow (Chair), Mike Rispin (Vice
that we have achieved success for the • We have continued our contact Chair), Michael F. Roach (Past Chair), Mike
first objective. This regular column with and education of elected Bruen, Leon J. Jacobs, Shane Yanagisawa,
has been my attempt to meet the officials and are creating a “top Erika Moonin, Mike A. Mooney, Pamela S.
goals of the third objective. I have underground projects” list to Moran, Mark Johnson, Matthew D. Preedy, Jon
always tried to be clear on the inner enhance these education efforts Klug, Edward Dowey, Tony O’Donnell, Robert
workings and developing news from ahead of anticipated federal A. Robinson, Grover Vargas, Sarah Wilson,
the UCA initiatives and report infrastructure investment. Paul C. Schmall, and Michael Vitale
where you, as members, can get more • We have created a dozen new
involved. committees with more than 100
Engaging more volunteers in new UCA volunteers by forming
objective two provides so many
benefits both for the individuals (continued on page 12)
2 june 2021 Tunneling & Underground Construction
ALWAYS ADVANCING www.terratec.co BANGKOK METRO Bangkok’s Mass Rapid Transit network is quickly expanding to meet the needs of this growing Asian Mega-City. For the 3.3km Orange Line Project, TERRATEC has delivered a complete tunnelling solution to contractor, Italian-Thai Development PCL. Having the final breakthrough completed a full month ahead of schedule, TERRATEC’s continuing success is a result of robust custom-made TBM designs, a readily available stock of TBM spares and consumables, and a highly-skilled team offering specialised TBM support and prompt onsite assistance throughout tunnelling operations. TUNNELLING SOLUTIONS METRO
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NEWSNEWSNEWS
Tunnel advocate confirmed to No. 2 spot in
Department of Transportation
T
he U.S. Senate confirmed the long-delayed Gateway rail project Transportation Trades Department,
Polly Trottenberg, by a to alleviate congestion between AFL-CIO.
vote of 82-15, to the No. New York and New Jersey, as well Trottenberg served on Biden’s
2 spot at the U.S. Transportation her focus on clean transportation transition team, worked in the
Department. Trottenberg is a New technologies and making streets safer Obama-era Transportation
York Policy veteran who will be for multimodal users, like cyclists and Department as assistant secretary and
deputy to Secretary Pete Buttigieg. pedestrians. under secretary for policy, and spent
She will bring more than 30 years Trottenberg’s most recent post 12 years working on legislation as a
of experience to helping President was New York Mayor Bill de Blasio’s Senate aide for Democrats including
Joe Biden sell his $2.25 trillion Department of Transportation Charles Schumer (NY), the current
infrastructure package. commissioner. She has promised majority leader.
Bloomberg Government to seek bipartisan solutions for the Schumer said on the Senate
reported that Biden’s $2 trillion nation’s transportation needs. floor that he talked with Trottenberg
infrastructure plan faces pushback “Throughout my career, I “regularly” about Gateway. During
from Republicans and corporations always valued the ability to work her confirmation hearing, Trottenberg
opposed to the tax increases proposed with colleagues across the aisle,” agreed to prioritize the rail and
to pay for the plan. Trottenberg, she said at her nomination hearing tunnel project, calling it a “project of
whose nomination was opposed by 15 on March 3. national significance.”
Republicans, drew criticism over her “Her understanding of The Biden infrastructure package
efforts in New York City to regulate transportation issues will help would double transit spending,
rideshare companies such as Uber the administration work to get according to the White House,
Technologies Inc. and Lyft Inc. a package across the finish line, providing $85 billion to modernize
Democrats lauded her support of said Greg Regan, president of the public transportation. n
Tunnel linking Northern Ireland and Scotland proposed
H
igh Speed Rail Group (HSRG) of Northern Ireland post-Brexit.” the Scottish parliament and that there
a group of rail industry experts Jim Steer, an HSRG board is a “feasible path to its funding from
has created a proposal for a member, said, “There is an urgent the UK Exchequer that does not
tunnel under the Irish Sea that would need for both new and improved adversely impact on other transport
link Northern Ireland to Scotland and transport links between the four funding.”
create better connectivity between the nations of the United Kingdom, A government spokesperson
four constituent parts of the United which have been systematically said, “We have asked Sir Peter
Kingdom. neglected for too long. Hendy to make recommendations
The Guardian reported that the “Cross-border travel markets on how to improve transport
submission from HSRG is expected for rail were growing strongly over connectivity between Scotland, Wales,
to be reviewed by Sir Peter Hendy, the period to 2019. Travel generates Northern Ireland and England. His
who is expected to publish his interim economic value, but the opportunity recommendations will be published
report within weeks. for further economic stimulus from in due course.”
The proposed tunnel would link this source will be lost if transport The prime minister first suggested
the towns of Stranraer and Larne, network capacity constraints are not connecting Stranraer in Scotland to
which are 50 km (31 miles) apart addressed. Larne in Northern Ireland by bridge
but a preferred route for the tunnel, “Building on the transformative three years ago, an idea that was
based on 120-year-old research by impact of HS2, HSRG are calling widely derided by engineers.
the Victorian engineer James Barton, for these cross-border rail links to Experts raised concerns about
would be diverted to avoid Beaufort’s be addressed as a matter of urgency, the practicality of constructing a
Dyke, a 305-m (1,000-ft) deep trench safeguarding the strength of the bridge across the stormy stretch of
in the Irish Sea. whole of the UK economy in the water, which is more than 305-m
According to the HSRG, the years ahead.” (1,000-ft) deep in places, and said
tunnel would bind Northern Ireland The pitch submitted to the review would require dozens of support
closer to Great Britain and would claims the proposal has the backing towers at heights “never achieved
“address problems in economic status of the Northern Ireland assembly and anywhere in the world.” n
4 JUNE 2021 Tunneling & Underground Construction
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NEWSNEWSNEWS
Gateway project will be a priority for
the Biden administration
U
.S. Transportation Secretary who in 2018 threatened to shut order to get there,” Buttigieg said. The
Pete Buttigieg told lawmakers down the government if a spending process involves reviewing anything
that the Gateway rail tunnel bill directed federal funding for the that might have changed since the
linking New York and New Jersey tunnel. Gateway was ineligible for draft was issued, and coordinating
is of national significance and as federal taxpayer money, the Trump with other federal agencies like the
such, the Biden administration is administration said, because New U.S. Army Corps of Engineers, as
prioritizing the project. York and New Jersey hadn’t pledged well as state agencies that might have
“This is a regional issue, but one enough cash. jurisdiction, he said.
of national significance because if Buttigieg said the Federal Rail Angelo Roefaro, a spokesman
there were a failure in one of those Administration and Federal Transit for Senate Majority Leader Chuck
tunnels, the entire U.S. economy Administration (FTA) are working Schumer, said Buttigieg has indicated
would feel it,” Buttigieg told members with New Jersey Transit and the Port to the New York Democrat that
of the House Transportation and Authority of New York and New the environmental review will be
Infrastructure Committee. Jersey, as well as with Amtrak and the approved in May.
Crains New York Business Gateway Development Commission, “I’ve said that the new
reported that Buttigieg provided on updates to a draft environmental administration could break Trump’s
lawmakers with his first update of impact statement issued in 2017. petty Gateway roadblock with the
the project. The project was stalled The impact statement is “a big
by former President Donald Trump part of what needs to be completed in (continued on page 8)
6 JUNE 2021 Tunneling & Underground Construction
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NEWSNEWSNEWS
Sydney Metro West receives major planning approvals
T
he Sydney Metro West Second, Sydney Metro has Olympic Park, North Strathfield,
project has received two received planning approval for two Burwood North, Five Dock, The
major planning approvals planned precast facilities at Eastern Bays, Pyrmont and Sydney CBD.
in readiness for the tunnel boring Creek, which are to contribute to the Future planning stages are
machines to start working by the end construction of Sydney Metro West. required for major civil construction
of 2022. The two facilities will manufacture works such as station excavation
The planning approvals for the 148,000 precast concrete segments and tunneling between The Bays
project are being done in stages for the 24-km (15-miles) twin tunnels and Sydney CBD, for tunnel fitout,
because of the project size. between Westmead and Sydney station building and operation of
First, the Sydney Metro West CBD. Once built, it is estimated that the line between Westmead and the
Project Concept has received planning it will take passengers 20 minutes to central business district.
approval from Westmead to Sydney’s travel from Parramatta to Sydney Construction on the Sydney
central business district and for the CBD. Metro West project started in late
station excavation and tunneling Stations have been confirmed 2020. The first tunneling contracts are
between Westmead and The Bays. at Westmead, Parramatta, Sydney likely to be issued in mid-2021. n
Gateway: Project would repair tunnels under Hudson
(continued from page 6)
up that pen and heeded the call to trains under the Hudson River.
‘flick of a pen,’” Schumer said in a free the ‘hostage’ that is Gateway.” Amtrak said it will allow for twice as
statement. “The Biden administration The tunnel would carry Amtrak many trains to run under the Hudson
and Secretary Buttigieg have picked and New Jersey Transit commuter River, including those that are part
of its Northeast Corridor service
that connects Boston, New York and
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“The FTA is working closely
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process prescribed in law, which is
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picture when it comes to funding,”
P R O V I D I N G I N N O VAT I V E S O LU T I O N S Buttigieg said.
The Gateway Development
FOR TUNNELING PROJECTS Commission said in a statement
after the hearing that “we applaud
Secretary Buttigieg’s public
commitment to the Gateway
Program, particularly confirming
that the Hudson Tunnel Project is
a project ‘of national significance’
and setting a rapid timeline
for completing the project’s
environmental review.”
The commission said it’s working
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microtunneling | tbm tunneling | hand tunneling | shaft work to complete the environmental
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CONSTRUCTION CORPORATION 21st Century rail link between New
York, New Jersey and the rest of the
Northeast Corridor.” n
8 JUNE 2021 Tunneling & Underground Constructiontuc&
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NEWSNEWSNEWS
First tunnel boring machine reaches future Wilshire/
LA Cienega subway station
T
he first of two tunnel boring were manufactured in Germany underground subway project that will
machines (TBM) working on by Herrenknecht AG. Metro has extend the Metro Purple Line from its
the D Line (Purple) Extension contracted with Skanska Traylor Shea terminus in Koreatown to Westwood/
project in Los Angeles, CA broke (STS), a joint venture to design and VA Hospital in West Los Angeles.
through to the Wilshire/La Cienega build the first section of the project. Section 1 is expected to be completed in
subway station in Beverly Hills. The $9.3-billion Metro Purple 2023, Section 2 in 2025 and Section 3 in
Metro announced that tunneling Line Extension is a 14-km (9-mile) 2027. n
for the first 6.4-km (4-mile) section of
the subway project is now two-thirds
complete. More than 90 percent of
the tunnels have been mined safely
and Metro anticipates completing
tunnel mining in summer 2021.
Excavation for all three subway
station boxes beneath Wilshire
Boulevard has been completed.
Elsie, the 910-t (1,000-st), 122-m
(400-ft) long TBM, started west at
the Wilshire/Fairfax station on May
29, 2020, and broke through to the
Wilshire/La Cienega station site
about 1.6 km (1 mile) away on Feb.
25, 2021.
Reaching this milestone is a
OUR
significant win for Metro. Section 1
of project tunneling has presented
challenges that have been successfully
overcome by the project. En route
KIND OF
to Wilshire/La Cienega, the agency’s
modern, high-tech TBMs have mined
through a unique combination of soils
and geologic conditions, including tar
PLAYGROUND
sands and methane gas.
Metro’s TBMs were first lowered
into the ground at Metro’s Wilshire/
La Brea station site in the Miracle
Mile area of Wilshire in October 2018.
While advancing, the TBM tunneled This is the natural habitat for Brokk’s compact giants.
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will have mined nearly half a million
cubic yards of earth. The TBMs
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NEWSNEWSNEWS
Canada to invest nearly $15 billion
for transit projects
T
he Canadian government announced plans to invest achieved with this investment. I am confident that Toronto
$14.9 billion for public transit project over the next will receive its fair share of funding from this initiative and
eight years. The plans include permanent funding of that it will make a significant contribution to our economic
$3 billion per year for Canadian communities beginning in recovery in the wake of COVID-19. Our share of this
2026-27. investment will mean transit expansion, transit vehicles
According to a government news release, “This and other system upgrades, jobs and a greener city.”
[commitment] provides cities and communities the Markham mayor Frank Scarpitti stated, “This is a
predictable transit funding they need to plan for the future, positive sign for the Yonge North Subway Extension,
and is part of our plan to create one million jobs, fight York Region’s top transit infrastructure project. It is one
climate change and rebuild a more sustainable and resilient of the most studied and justified transit projects in the
economy.” country and we cannot wait any longer to get shovels in
“When we invest in public transit infrastructure, we the ground. By earmarking these infrastructure dollars,
are supporting good middle-class jobs, creating better the federal government is confirming its commitment to
commutes, fighting climate change and helping make life making public transit investment a high priority.”
easier and more affordable for Canadians,” said Prime Ontario’s transportation minister, Caroline Mulroney,
Minister Justin Trudeau. “We will continue to do what it announced that Ontario had selected five priority projects
takes to ensure our economic recovery from COVID-19 that it hoped the federal government would fund. Four of
and build back a more resilient country for everyone.” those projects are in Toronto, part of the transit expansion
Reaction from local municipal leaders was swift. “This plan that Premier Doug Ford announced in April 2019.
is great news for Toronto and our transit system,” Toronto Those four projects include:
Mayor John Tory said. “Over the coming days and weeks,
we expect that the details of this commitment will show • Building the Ontario Line Subway between Don
the tremendous impact on Toronto transit that will be Mills Road / Eglinton Avenue East and Exhibition
Place.
• Extending the TTC’s Line 2 Bloor – Danforth
subway to McCowan Road / Sheppard Avenue
East.
• Extending the Line 1 Yonge – University subway
to Highway 7 / Yonge Street.
• Extending the Line 5 Eglinton light rail transit line
to Toronto Pearson International Airport.
In a surprise part of the announcement, Mulroney
identified a light rail transit line in Hamilton as Ontario’s
fifth priority project for federal funding. The Ontario
government controversially canceled the project in
December, 2019 after previously committing $1 billion
toward building the line.
The renewed support for the project may, however,
result in a shorter line than Ontario and the City of
Hamilton had earlier planned. n
10 JUNE 2021 Tunneling & Underground ConstructionMove Your Career
in the Right Direction
Find resources for all phases of your career path
with your UCA membership.
Professional Get Involved Career Center
Development Inspire the next generation of Find a new job or career
Earn PDH credits and stay underground engineers and insights at the UCA Career
current with a range of support Down for That, an Center and connect with
professional development exciting workforce initiative at your next great job.
opportunities, both online undergroundcareers.org Create an account at
and in person. tunnelingjobs.smenet.org
Make the most of your membership with UCA resources.
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NEWSNEWSNEWS
King County Ship Canal Water Quality
Project TBM launched
T
he 6.6-m (21.8-ft) diameter vertical shafts in Ballard, East The tunnel boring machine named Mudhoney
earth pressure balance tunnel Ballard, Fremont, Queen launched on April 19.
boring machine (TBM) named Anne and Wallingford can
Mudhoney launched in Seattle, collect stormwater and
WA to begin creation of the 4.3-km sewage flows from each
(2.7-mile) long tunnel that will store basin and send them 64 m
combined sewer overflow as part of to 128 m (40 to 80 ft) below
the city’s consent decree with the U.S. ground to the tunnel. To
Environmental Protection Agency. bring flows from Queen
The $225-million underground Anne into the storage tunnel,
storage tunnel is part of the larger an additional 12-m (8-ft)
$570 million King County Ship Canal diameter conveyance tunnel
Water Quality Project. underneath the Ship Canal
Lane Construction, contractor connects the vertical shafts in
on the tunnel portion of the project, Queen Anne and Fremont.
launched the TBM on April 19 and New pipes will connect the
plans to have the overflow tunnel existing sewer system to the
ready by 2025. When completed, the shafts.
tunnel can, on average, prevent 75 In some parts of Seattle,
million gallons of polluted stormwater sewage and stormwater share
and sewage from entering the a set of pipes in a combined sewer and is more than 4,300 m (14,200
neighboring waterways. The tunnel and stormwater overflow system that ft) long. The machine includes 18
will capture and temporarily hold can send untreated co-mingled water double-disc cutters, 48 scrapers and
more than 29.6 million gallons during into the environment. The region is 16 bucket cutters, with the ability to
heavy rains. under federal order to prevent the remove about 360 kt (400,000 st) of
Engineering News Record sewage releases. dirt during the dig, including 32 m
reported the storage tunnel is part Parts for the TBM were shipped (105 ft) under the Aurora Bridge.
of the larger Ship Canal project to Seattle from Germany and Smaller tunneling machines will
from Seattle Public Utilities and the assembled in Ballard. create conveyance tunnels under the
King County wastewater treatment The machine, which requires 10 Ship Canal between Fremont and
division. Along the tunnel path, five to 15 operators, was built new in 2020 Queen Anne and in Ballard. n
Chairman’s Column: It has been a privilege
(continued from page 2)
by the many long phone calls and two years and I hope that we have
• more than a dozen U.S. sub- difficult decisions that had to be pushed the ball down the field in a
committees, each to support one made. positive way. The staff at SME have
ITA Working Group. We now look forward with a been fantastic and supportive, as
revitalized desire to get out and always, and deserve more thanks than
Looming over the past two meet again in person, a refreshed I can adequately give. I look forward
years has been COVID-19. The and expanded pool of active to supporting Mike Rispin as he takes
impact on our businesses and industry volunteers and we have a over in the chair and as I slide into
professional association has been new strategic plan to capture this the past-chair role of being one of
challenging. UCA and SME both enthusiasm and turn it purposely to the old guys complaining from the
still exist — quite an achievement the benefit of the tunnel industry. balcony in the Muppet Show!
given the many casualties among Finally, but most important, it It has been fun. Thanks very much
professional associations. We has been my privilege to serve you everybody. n
have run virtual events with some as the Chair of UCA. The Executive
success and kept up with industry. Committee has put in a huge amount
Robert Goodfellow
I would characterize this period of work on your behalf over the past UCA of SME Chair
12 JUNE 2021 Tunneling & Underground ConstructionMake an Exciting
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NEWSNEWSNEWS
Record advances at the Brenner Base Tunnel
by double-shield tunnel boring machines
M
iners in the Brenner Base covered 860 m (2,821 ft) in one month. machines in the Brenner main tunnels
Tunnel are pushing ahead The contracting joint venture BTC had already covered more than 50
rapidly with the major rail S.c.a.r.l. (Astaldi S.p.A., Ghella S.p.A., percent of the total distance toward
project. On March 31, 2021, they P.A.C. S.p.A. and Cogeis S.p.A.) thus their lot boundary. In stable geologies,
achieved a new record while excavating achieved a peak advance rate at the double-shield TBMs are predestined
the main tubes in South Tyrol — 860 m Mauls jobsite. For March 2021, the for good tunneling performance. As
(2,821 ft) of tunnel bored and lined in Brenner Base Tunnel project owner, the TBM bores, the excavated tunnel
one month. Austrian-Italian BBT SE, announced is concurrently lined with concrete
On the Italian construction lot an average daily advance rate of 27.7 segments.
“Mauls 2-3” of the Brenner Base m (91 m) for Virginia. The daily best At a total length of 64 km (40
Tunnel, three Herrenknecht tunnel performance was 36.75 m (120.6 ft). miles), the Brenner Base Tunnel being
boring machines (TBMs) are boring Matthias Flora, sales and built under the direction of Austrian-
from south to north. They are project manager at Herrenknecht, Italian BBT SE will be the longest
excavating the two main tubes as well as congratulated the team on the jobsite, underground rail link in the world.
an exploratory and later service tunnel “Our customer BTC’s crews are It crosses beneath the Alps between
12 m (39 ft) below. In March 2021, a absolute top professionals in their field. Innsbruck in Austria and Franzensfeste
new record was set by one of these Congratulations and our utmost respect (Fortezza) in South Tyrol/Italy as a
three machines: the double-shield TBM for this achievement.” particularly efficient flat trajectory, that
(Ø 10.65 m or 35 ft) named “Virginia” By early April 2021, the two is, with very low gradients. n
ITA accepting award nominations
T
he 7th edition of the Even Better” replacing “Overcoming better; Oddities of the Underground;
International Tunnelling the challenges.” Innovative and contributing
Association’s (ITA) This year the entries can be Underground spaces; Young Tunneller
International Tunnelling and submitted in eight categories: of the Year.
Underground Space awards welcomes Major Project of the Year - More Entries can be submitted until
new applications. than €500 million; Project of the June 30, 2021. The submission
ITA Awards 2021 will be a digital Year - between €50 million and requirements and selection process are
event. For this edition, a small change €500 million; Project of the Year stated in the ITA Tunnelling Awards
is proposed in the categories notably including Renovation - up to €50 website: https://awards.ita-aites.org/
to better specify what is expected in million; Technical Innovation of the account-creation. More information
the category “Beyond Engineering - Year; Beyond Engineering - making can be found at https://awards.ita-aites.
Making Underground Works Projects underground works projects even org. n
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Feature Article 1
®
Design and construction considerations for
intersecting tunnels — Charleston, SC
F
ounded in 1670, Charleston, SC is one of oldest Intelligent Transportation Systems (ITS); and new, energy-
cities in the nation. Since its inception, the city efficient traffic signals. The infrastructure reinvestment
of Charleston has experienced difficulties with (Phases 2 and 3) will consist of constructing improved
stormwater management. With rising tidal waters and and additional surface collection systems throughout
stronger storms, stormwater management has only become parts of the basins, drilling and sinking several shafts,
more difficult. Tunnels and trenchless technology have boring a deep tunnel system to connect the shafts,
roots in Charleston dating back to 1928 when a system (Phase 4) constructing an outfall from the pump station
of water supply tunnels was constructed to bring a new to the Ashley River and (Phase 5) constructing a new
water supply from the Edisto River and Foster Creek pump station adjacent to the Ashley River. Phase 3 was
to the Hanahan Water Treatment Plant to supplement designed by Black & Veatch and Davis & Floyd Inc.; the
ground water sources. Today nearly 80 km (50 miles) of contractor was Jay Dee Contractors Inc.; and the support
tunnels have been constructed or designed in and around of excavation design was completed by FK Engineering.
Charleston for water, waste water and storm water
conveyance. Geological conditions and concerns
The city of Charleston first utilized tunnels to address The geology of the Charleston peninsula is that of
storm water in 1999 for their Meeting Street/Calhoun an estuary, and as such, the shallow deposits (surficial
tunnel. The city selected tunneling to minimize utility soils) are influenced by a combination of marine and
impacts and public disruption. Two additional storm continental processes. The surficial soils were deposited in
water tunnels have been completed since the Meeting a range of sedimentary facies including fluvial, overbank,
Street/Calhoun tunnel. The Market Street Drainage tidal marsh, tidal channel, tidal flat, lagoon, beach, barrier
Improvements Project tunnel was completed in 2013 and island and shallow marine. Characterized by its extremely
the final phase of the project is pending construction. The low shear strength and high clay content, the surficial soils
US17 Spring/Fishburne Drainage Improvements Project are susceptible to significant consolidation and settlement
tunnel system was completed in summer 2020. Additional over time. As a result, large portions of the peninsula,
basins in the Charleston peninsula also have conceptual including city streets, are slowly subsiding. However, 15 to
tunnel systems that may be implemented in the future. 21 m (50 to 70 ft) below these surficial soils is a geologic
The city of Charleston’s Spring/Fishburne US17 formation locally referred to as the Cooper Marl. The
Drainage Improvements Project is a five-phase program Cooper Marl is a relatively thick layer 45 to 60 m (150
designed to alleviate flooding in two drainage basins to 200 ft) of olive-green, calcareous, medium-to-stiff,
covering approximately 202 ha (500 acres), or about sandy/clayey silt. It is an excellent engineering medium
20-percent of the Charleston peninsula. This project has used extensively for its load-bearing and self-supporting
several objectives: to improve the mobility, efficiency, attributes. Large buildings are almost exclusively founded
emergency preparedness and community livability; on pile supports that extend into the Cooper Marl. The
and, most importantly, to alleviate many of the flooding Cooper Marl’s strength and standup time can primarily
problems by reinvesting in the infrastructure. be attributed to the calcareous bonds, as depicted in Fig. 1.
The transportation advancements (Phases 1 and 2) However, these bonds are easily broken by traditional and
incorporated safer travel lanes for vehicles; improved modern mechanical tunneling methods.
intersections for pedestrian safety and vehicle efficiency;
Design
The tunnel system was designed to capture the storm
Steve Kirk, Michael Miglioretti, Kyle water flows from select low points within the Spring and
White, Lindsey Schneider, Jeffrey P. Fishburne basins via drop shafts and transport the storm
water through the tunnel system via a pump station and
Kolzow outfall to the Ashley River. The tunnel was designed to
a depth of 37 to 46 m (120 to 150 ft) below the ground
Steve Kirk, senior engineering project manager, surface to ensure adequate clearance was maintained
City of Charleston; Michael Miglioretti, Kyle White, from the surficial soils and existing/future building piles,
member UCA of SME and Lindsey Schneider are bridge piers and existing waste water tunnels in the
field engineer, resident engineer and civil engineer, project vicinity. The system is comprised of approximately
Black & Veatch and Jeffrey P. Kolzow, member UCA 2,566 m (8,420 ft) of cast-in-place 2.4 to 3.6 m (8 to 12
of SME, is project engineer, Jay Dee Contractors, Inc. ft) finished internal diameter (ID) tunnels, four large-
email MigliorettiM@bv.com. diameter access shafts 6 to 9 m (20 to 30 ft ID) and eight
drop shafts 122 to 137 cm (48 and 54 in. ID).
16 JUNE 2021 Tunneling & Underground ConstructionFig. 1
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Cooper Marl exposed during adit excavation and initial support.
The system design includes four
access shafts and two intersecting
tunnels. The access shafts were
generally referred to as follows:
Lockwood Drive, Harmon Field,
Cannon Street and Coming Street.
The two tunnels were the Main Line
Tunnel and the President Street
Branch Tunnel. The Main Line Tunnel
extended about 680 m (2,225 LF)
from the Lockwood Drive Access
Shaft approximately 0.3 percent
upgrade to the Intersection, and then
895 m (2,935 LF) approximately 1.0
percent upgrade to the Coming Street
Access Shaft. The President Street
Branch Tunnel runs about 396 m
(1,300 LF) from the Harmon Field
Access Shaft 0.3 percent downgrade
to the intersection, then about 680 LF
0.3 percent upgrade to the Cannon
Street Access Shafts. This “V” shaped process was repeated until the caisson was extended
alignment serves to ensure that any entrained air can through the surficial soils and Cooper Marl to the full
travel back to either the Harmon Field Access Shaft or depth of the caissons. The shafts were excavated within
Cannon Street Access Shaft and that storm water flows to the surficial coils with a clamshell-type bucket mounted
the Lockwood Drive Access Shaft, where a wetwell, pump on a crane, and within the Cooper Marl using a small
station and outfall will be constructed in future phases. mechanical excavator and muck box for spoil removal.
The intersection location and geometry was a result This excavation and support methodology allows for
of construction easements and hydraulic boundary the initial support to act as the final shaft lining. Wall
conditions. Figure 2 provides an aerial view of the surface thickness design required a minimum of 46 cm (18 in.) of
above the intersection. The President Street Branch reinforced concrete. This thickness applied for both 6-m
Tunnel was designed to run directly beneath President and 9-m (20-ft and 30-ft) shafts. An approximately 1.5 m
Street in downtown Charleston. The Main Line Tunnel (5 ft) 6 m (20 ft shafts) or 2.5 m (8.5 ft) 9 m (30 ft shafts)
alignment generally follows the Septima P. Clark Parkway thick concrete invert plug was designed to account for
(US17), locally referred to as the “Crosstown,” which buoyancy forces.
cuts across the Charleston peninsula. Stakeholders along The Lockwood Drive Access Shaft design consisted
President Street and the Septima P. Clark Parkway include of a two-pass construction method. Initial support
utilities, schools, homes and local businesses. The resulting through the surficial soils, and a minimum of 3 m (10 ft)
Intersection design helped minimize impact to these into the Cooper Marl, was to be constructed of concrete
stakeholders. caisson, sheet piling, secant piles or slurry wall through
Support of excavation for the tunnels was designed the surficial soils. Following support 3 m (10 ft) into the
for a two-pass installation method. The cast-in-place Cooper Marl, initial support consisted of ribs and lagging,
concrete final lining for the tunnel system used liner plate or other contractor-selected support through
polypropylene fibers to reduce crack frequency and the Cooper Marl. The final lining design consisted of 45-
width. Steel reinforcement was only used at tunnel-adit cm (18-in.) minimum reinforced cast-in-place concrete.
junctions, tunnel-shaft junctions and at the Main Line
Tunnel-President Street Branch Tunnel intersection Project construction
(the Intersection). The typical minimum thickness of Lockwood Drive Access Shaft. The first shaft
the concrete lining was 31 cm (12 in.). The Intersection constructed was the Lockwood Drive Access Shaft
concrete minimum thickness was 51 cm (20 in.). (LDAS). The LDAS acted as the primary support shaft
Three of the four access shafts (Coming, Cannon and for the Main Line Tunnel construction and is the future
Harmon Field) were constructed using the caisson-sinking location of the tunnel system pump station. The Main Line
method. A cast-in-place circular reinforced concrete Tunnel invert meets the LDAS about 10 m (35 ft) above
caisson could sink under its own weight as the native the base slab invert. This 10 m (35 ft) sump will be used
material in the center of the structure was excavated. for future tunnel dewatering pump installation and act as
Excavation was stopped at regular intervals to allow a sediment basin for the tunnel system.
casting of the subsequent portions of the caisson. The The LDAS is situated on a marsh adjacent to the
Tunneling & Underground Construction JUNE 2021 17Fig. 2
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Feature Article 1
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Aerial view of surface above the intersection; President Street runs top-left to bottom-right
and the Septima P. Clark Parkway is the six-lane road running from bottom-center to top-
center. annulus through a series
of 5-cm (2-in.) PVC piping
running vertically through
the shaft walls, reducing
the skin friction that could
otherwise cause the caisson
to “hang-up” in the Cooper
Marl. The pipes expelled the
bentonite to the outside of
the caisson walls. Following
excavation and sinking, the
annulus space outside of the
caissons was grouted to fill
the voids prior to excavating
for the tunnel eyes.
The contractor and its
design engineer elected to
increase the caisson wall
thickness as an additional
measure to facilitate
sinking in the Cooper Marl
formation. The 6-m (20-ft)
Ashley River. To account for flooding from extreme high- ID shafts (Coming Street and Cannon Street) were 0.7 m
tide events and tropical storms, the shaft area was built up (2.5 ft) thick. The Harmon Field Access Shaft 9 m (30 ft
from EL 0.5 m (1.5 ft) to about EL 3 m (10 ft) with clean ID) was 1 m (3 ft) thick. The depths of the shafts ranged
sand, general fill and a stoned surface. from 37 to 46 m (120 to 150 ft).
Support of excavation in the surficial soils utilized The contractor was required to prevent
steel sheet piles supported internally with steel ribs. The uncontrollable sinking, which is more typical and
sheet piles were socketed approximately 3 m (10 ft) in problematic in the weaker surficial soils above the
the Cooper Marl. Excavation was accomplished with a Cooper Marl. In order to prevent uncontrollable sinking,
clamshell bucket and a small mechanical excavator. The the contractor preloaded the shaft with hydraulic
contractor installed a 1.5-m (5-ft) tall concrete collar jacks. The hydraulic jacks were anchored to a concrete
which transitioned the support of excavation from the counterweight with steel threaded rods and applied
sheet piles to a ribs and lagging system. The ribs and force to a steel frame that was placed on the shaft. As
lagging extended through the Cooper Marl to the invert a result, the hydraulic force was exerted onto the shaft.
of the shaft excavation. The pressure applied was generally representative of the
The LDAS used a 9-m (30-ft) internal diameter cast- next concrete lift, or approximately 145 to 163 t (160 to
in-place concrete final lining. The concrete final lining 180 st). If sinking was noted while the hydraulic jacks
was a minimum of 45 cm (18 in.) thick and reinforced were active, force would continue to be applied until no
with steel rebar. The shaft used a 2.5-m (8.5-ft) thick base additional sinking was noted. The hydraulic jacks were
slab with the top of slab at approximately EL -52 m (-170 applied to the shafts in order to prevent uncontrollable
ft). Shaft concrete final lining was installed from EL -52 sinking during concrete placement. The hydraulic jacks
m (-170 ft) to EL -9 m (-30 ft). The final lining terminates were also utilized during the excavation process in order
at EL -9 m (-30 ft) where it will connect to future wet well to encourage incrementally controlled sinking versus
and outfall construction. unexpected and uncontrollable sinking.
The caissons were constructed in 3.6-m (12-ft) lifts
Caissons. The Coming Street, Cannon Street and with a modular set of 4.2-m (14-ft) tall internal and
Harmon Field Access Shafts were constructed using the external concrete forms. The additional height was used
caisson sinking method. In order to facilitate sinking, the for 0.3 m (1 ft) of overlap at the bottom and 0.3 m (1
contractor used a “cutting shoe.” The cutting shoe was ft) of gap at the top for water-stop installation. These
a tapered cylindrical steel structure built with a larger forms were only tied together at the top of the forms;
outside diameter than the typical caisson cross-section. wall-penetrating form ties were not used. The shafts
The cutting shoe aided sinking by reducing the bearing were maintained in a flooded state while excavation
surface of caisson and creating a shear plane to loosen progressed through the surficial soils. The flooded state
excavatable material and direct soils to the interior of the prevented the surficial soils from running into the interior
caisson as the shaft was sunk. In addition to the cutting of the shaft during excavation and sinking activities. Once
shoe, the contractor pumped bentonite slurry into the the caisson reached 3 to 6 m (10 to 20 ft) of embedment
18 JUNE 2021 Tunneling & Underground Constructiontuc&
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into the Cooper Marl, the interior could be dewatered. excavation progressed. Voids behind the initial support
were filled with grout. The remaining adits were excavated
Tunnel and adit initial support. The Main Line Tunnel via hand-mining techniques.
(approximately 1,650 m (5,400 LF) was excavated upgrade Excavation advancement in the adit tunnels was
from the Lockwood Drive Access Shaft to the Coming generally consistent throughout the project. Following
Street Access Shaft. Means of excavation included a initial support and breakout from either of the primary
refurbished open-face soft-ground tunnel boring machine tunnels, the contractor would “bench” the excavation so
(TBM). The TBM bore was approximately 4.5 m (15 ft) that the crown of the excavation was one-to-two initial
and utilized a ribs-and-lagging initial support system. support sets ahead of the spring-line and invert support.
The initial support consisted of steel ribs (W4x13) on Initial support consisted of rolled steel ribs (W4x13) for
approximately 1.5-m (5-ft) centers with mixed hardwood the crown and steel beams (W4x13) supporting the ribs.
lagging between the sets. The ribs were assembled within The steel was typically installed on 1.5-m (5-ft) centers
the tail shield of the TBM and expanded tightly against with mixed hardwood lagging. Voids behind the initial
the ground after the machine had moved forward. Muck support were filled with grout.
was removed from the heading using rail-mounted muck
cars. Tunnel and adit final lining. The tunnel and adits used
The first 67 m (220 ft) of the Main Line Tunnel was a cast-in-place concrete final lining. The concrete was
converted to a 4.5 m by 4.5 m (15 ft by 15 ft) horseshoe. reinforced with polypropylene fibers. Steel reinforcement
This horseshoe section of the tunnel allowed for the was only used at tunnel-adit junctions, tunnel-shaft
installation of a rail switch for expediting the tunnel junctions, and at the Intersection. The tunnel concrete
excavation. Two muck car trains were utilized during forms were reusable, collapsible steel forms. A keyway
excavation. While one train was being loaded with was installed at the face of each concrete segment/
excavated material, the other train would be unloaded placement. The pumping location moved as needed to
into a muck area on the surface. Each train generally facilitate the concrete pump capabilities. Concrete was
consisted of four 15 cy muck cars, a diesel-powered pumped through a steel slickline with pumping distances
locomotive, and a flat car for supplying the initial support reaching 610 m (2,000 ft).
system to the TBM. A tail tunnel was also utilized to The Main Line Tunnel finished internal diameter
facilitate unloading muck trains. The tail tunnel was was 3.6 m (12 ft). The concrete was placed in a series of
constructed with ribs & lagging initial support and segments ranging in length, typically 24 to 37 m (80 to
ultimately abandoned with flowable fill grout. 120 LF). Concrete segment lengths would generally vary
The President Street Branch Tunnel (approximately to account for tunnel alignment curvature or planning
610 m (2,000 LF)) was excavated downgrade from the around junctions. Concrete for the Main Line Tunnel
Harmon Field Access Shaft to the Main Line Tunnel was pumped from the surface from the Lockwood Drive
Intersection, then upgrade to the Cannon Street Access Access Shaft the Courtenay Drop Shaft, the Cannon
Shaft. Means of excavation included a refurbished open- Street Access Shaft and the Ashe Drop Shaft. The
face soft-ground TBM. The TBM bore was approximately formwork was advanced mechanically with an electric-
3.3 m (11 ft) and utilized a ribs and lagging initial powered hydraulic form carrier. Concrete was placed at
support system. The initial support consisted of steel an approximate 0.3 percent grade from the Lockwood
ribs (W4x13) on approximately 1.2-m (4-ft) centers with Drive Access Shaft to the Intersection and approximately
mixed hardwood lagging between the sets. The ribs were 1.0 percent grade from the Intersection to the Coming
assembled within the tail shield of the TBM and expanded Street Access Shaft.
tightly against the ground after the machine had moved The President Street Branch Tunnel finished internal
forward. Muck was removed from the heading utilizing diameter was 2.4 m (8 ft). The concrete was placed in
rail mounted muck cars. The President Street Branch a series of segments ranging in length, typically 27 to
Tunnel did not utilize a tail tunnel or switch during the 38 m (90 to 125 LF). Concrete segment lengths would
excavation process. generally vary to account for tunnel alignment curvature
There were eight adit tunnels extending from the or planning around junctions. Concrete for the President
primary tunnels to the previously installed drop shafts. Street Branch Tunnel was pumped from the surface from
Along the Main Line Tunnel were seven adits with the Harmon Field Access Shaft and the Cannon Street
the remaining adit extending off the President Street Access Shaft. The formwork was advanced mechanically
Branch Tunnel. Adit tunnel excavation ranged from with an electric-powered hydraulic form carrier. The
approximately 1.5 m (5 LF) to 163 m (535 LF) along concrete was placed approximately 0.3 percent downgrade
the alignment. The longest adit, extending to the Cherry from the access shafts to the Intersection, creating a
Street Drop Shaft, was excavated with a combination of “v” shape from the Intersection up to both access shafts
mechanical (roadheader) and hand-mining techniques. (Harmon Field and Cannon Street).
Muck was removed from the Cherry Street Adit with The finished internal diameter for the eight adits
a pair of skid steers traversing through the adit as the was 2.4 m (8 ft). The concrete was placed in a series of
Tunneling & Underground Construction JUNE 2021 19tuc &
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Fig. 3
Completed Intersection initial support; President Street Branch Tunnel (left) and Main Line Tunnel diameter at the
Line Tunnel. Intersection was potential air
entrainment and impact to the
hydraulic design of the tunnel
system. Addressing the entrained
air, the Project team proposed
casting pipes in the crown of the
Intersection concrete. The pipes
would connect the crowns of the
two 3.7-m (12-ft) diameter sides
of the Main Line Tunnel in order
to allow for air to flow upgrade
toward the Coming Street Access
Shaft, as originally designed. This
proposal was ultimately accepted
and pursued.
Another challenge regarding
initial support of the Intersection
was maintaining positive
ground support. The contractor
constructed two 3.7 x 3.7 m (12
x 12 ft) adits branching out from
the Main Line Tunnel. These
adits extended out into native
ground to receive the President
segments ranging in length, typically 3 to 15 m (10 to 50 Street Branch Tunnel TBM. The TBM would then “walk”
LF). Seven of the eight adits were completed with one to through the intersecting Main Line Tunnel and relaunch
three segments. The Cherry Street Adit, approximately through the opposite adit. The completed initial support
163 m (535 LF), required a series of segments to complete. system is displayed in Fig. 3.
Typical segments length was 15 m (50 LF), varying
as needed around curves or at the Main Line Tunnel Intersection final lining. The Intersection was the final
junction. Concrete final lining for the adits was designed concrete placed for the tunnel system. The contractor
and installed with a flat (0 percent) grade. was elected to complete the Main Line Tunnel, President
Street Branch Tunnel and adit final lining concrete prior
Intersection construction to forming and placing concrete in the intersection.
Intersection initial support. The proposed junction The concrete in the Intersection was formed with a
design needed to address a series of challenges. One of the combination of custom-built formwork along with
primary challenges was maintaining the minimum design repurposed 2.4-m (8-ft) ID formwork used for the
wall thickness in the Intersection. The designed wall President Street Branch Tunnel final lining, referred by
thickness in the intersection was 20 cm (8 in.) larger than the contractor as “fish mouth” forms.
the typical tunnel section (50 cm (20 in.) instead of 31 cm The concrete along the Main Line Tunnel used
(12 in.)). custom-built forms constructed out of steel ribs, timber,
The Main Line Tunnel TBM bored an approximate plywood and mixed hardwood lagging. The steel ribs
15-ft (180-in.) diameter tunnel. When accounting for the were rolled to an approximate diameter of 3.3 m (11
initial support, approximately four inches thick, or 20 ft). Between two steel ribs was plywood reinforced with
cm (8 in.) impacting the diameter, the resulting initial 1.5-m (5-ft) long two-by timber, resulting in 1.5-m (5-ft)
support diameter was approximately 437 cm (172 in.). The long “quadrant” pieces. Two quadrants bolted together
designed final internal diameter was 3.7 m (12 ft) along resulted in one 1.5-m (5-ft) long invert section piece.
the Main Line Tunnel 365 cm (144 in.). With the initial The preassembled quadrant pieces were mobilized to
support, this resulted in an approximate 36-cm (14-in.) the Intersection via locomotive along the President
projected wall thickness. In order to achieve the required Street Branch Tunnel. The quadrants were hoisted with
50 cm (20 in.) minimum, the contractor proposed reducing a previously installed steel monorail, assembled into
the Intersection opening to 3.3 m (11 ft) along the Main 1.5-m (5-ft) invert section pieces, and stored in the Main
Line Tunnel. This design would align inverts at the Line Tunnel for future installation. The concrete along
Intersection, but the crown would drop down about one the President Street Branch Tunnel utilized repurposed
foot along the Main Line Tunnel. 2.4-m (8-ft) steel formwork previously used for the
The primary concern regarding reducing the Main President Street Branch Tunnel concrete lining. The
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