Tunneling Innovation:
A Look at How HMM Is Helping Transform Tunnel Engineering and Construction The field of tunnel engineering and construction is constantly evolving. While basic tunneling methods may be the same, and Mother Nature is still the boss, technological advances are making construction more efficient, precise and with greater risk avoidance than in years past. In this article, we take a look at technological innovations and how they are being implemented from the perspective of Hatch Mott MacDonald (HMM). Launched in 1996 with 35 transit and tunneling staff, HMM has grown to be a multi-disciplinary consulting engineering firm with 2,300 staff in 65 offices across North America. Hatch Mott MacDonald’s parent companies, Mott MacDonald (MM) and Hatch, have a combined staff of 23,000 operating in more than 140 countries. “A fundamental focus of the business is delivering innovation solutions that are pragmatic and constructible,” said Randy Essex, HMM’s North American Practice Leader. “MM and HMM share tunneling-related innovations so that diverse clients can benefit from a global knowledge base.” Below, we highlight examples where innovations have been leveraged among a number of recent and ongoing projects. Toronto-York Spadina Subway Extension/Eglinton-Scarborough Crosstown LRT, Toronto Following a successful relationship on the Sheppard Subway Project in the 1990s, the Toronto Transit Commission (TTC) engaged HMM in 2008 to assist with the management and design of the Toronto-York Spadina Subway Extension (TYSSE). The $2.63 billion TYSSE consists of 5.4 miles of new rail service, approximately 4.2 miles of which will be housed in twin-bore, soft-ground tunnels. The line also includes six new cut-and-cover stations, associated cross-overs, cross-passages, storage track and yard connection. HMM, in joint venture with Delcan and MMM of Toronto, has provided overall program management for the project, integrating design contracts held by HMM for the twin tunnels, and six contracts for the cut-and-cover stations held by other consultants. 3D CADD Design TTC challenged HMM with delivering complete tender documents for the twin tunnels within an accelerated 18-month schedule, including site exploration. In order to meet TTC’s tight design schedule, HMM utilized seven packages within the Bentley software suite to design the tunnels, emergency egress buildings, cross passages, and pocket track structures in a fully integrated 3D model. By integrating all structural, mechanical, electrical and alignment elements into a single model, HMM was able to engage multiple design offices in the design effort, and was able to substantially streamline inter-disciplinary coordination and resolution of spatial conflicts. The 3D imaging capability also allowed TTC and affected third parties to visualize what would be constructed and where, strengthening TTC’s public outreach effort.
“Bentley software enabled HMM to meet critical schedule milestones during execution of the tunnel design for the TYSSE project. Multidisciplinary coordination through use of the 3D modeling environment, and graphical representations were key to enhancing communication and geometric understanding amongst team members, our clients, and our stakeholders,” said HMM’s Gary Kramer, Tunnel Design Manager.
Accelerated Start of Construction
Compensation Grouting Program One of the TYSSE stations, York University Station, will be located in proximity to the York University campus, which has a student and faculty population of about 40,000. The station is situated in the campus commons, shoe-horned in between two campus structures, the Schulich Building, which is part of the business school, and the York Lanes building, a campus retail mall. Given the inability to move the tunnels out from beneath the Schulich building, and the sensitivity of the structure, HMM developed a compensation grouting program to protect the building during tunnel construction. The use of the method was first introduced in North America on HMM’s St. Clair River Railway Tunnel Crossing in the mid 1990s.
Victoria Station Upgrade Project, London
MM was initially commissioned by LU in December 2006 to provide full production design and advisory services. Subsequently, in May 2010, MM’s contract was novated to the selected contractor, Taylor Woodrow and BAM Nuttall JV. The VSU project includes enlargement of the existing Victoria Line ticket hall, creation of an additional ticket hall and entrance, new pedestrian tunnels to ease passage within the expanded station (constructed with sprayed concrete linings through jet grout stabilized water bearing gravels), improvements associated with passenger evacuation, access for emergency services, and ventilation. Elements include nine new escalators, eight new elevators for step-free access, and modernization of the areas of the station not affected by the new works. An important feature is that this major upgrade must be carried out without impacting ongoing passenger services. BIM – An Essential Engineering Tool
The model was an LU engineering requirement. Secant piles forming the walls of the new north ticket hall are positioned within 10 ft of the culvert carrying the River Tyburn. The passenger tunnel linking the new ticket hall to the Victoria Line ducks under the culvert and scrapes over the southbound Victoria Line platform tunnel with only inches to spare. An escalator squeezes between the twin bores of the north and southbound platform tunnels, with a mere 12 in. clearance. “BIM is being used to resolve an incredibly complex spatial puzzle so that the new and old come together seamlessly – so everything fits the first time,” Dickson commented. “BIM is being used to check the very fine construction tolerances involved. Another success is that we’ve been able to take LU’s maintenance engineering staff, a key project stakeholder, on a virtual fly-through within the model, thereby addressing their concerns and obtaining their buy-in to the design. ” Prior to HMM’s winning Bentley’s Be Inspired Award in 2011, MM won the same award in 2010 for its BIM successes on the VSU Project. Structure Instrumentation and Performance
David Cook, who leads the MM monitoring team, said that “VSU has enabled us to apply our successful monitoring experience working in historic Amsterdam to equally sensitive conditions in central London.” Crenshaw/LAX Transit Corridor Project, Los Angeles
In contrast to the TYSSE project, where a fully integrated BIM model helped deliver 100 percent design and procurement documents, BIM technology was used on the Crenshaw Project to target two key project elements. One was the modeling of the two underground stations, where existing infrastructure and utilities were incorporated into a single model that facilitated space planning and preliminary design of the proposed bored tunnels, station envelope and access shafts.
East Side Access Project, New York The East Side Access project is a $7.3 billion rail link project that will give commuters on the Long Island Rail Road a “one-seat ride” into Grand Central Terminal, which is located on the east side of Manhattan. The largest single public infrastructure project being carried out in North America, it is incredibly complex. “We’re building a major new transport link in one of the world’s most densely developed cities,” commented Andy Thompson, HMM’s Construction Manager for the project. Since 2000, HMM has been providing program and now construction management services for the New York Metropolitan Transportation Authority. Given the highly variable ground conditions found in Manhattan and Queens, the project has demanded a broad range of underground construction technology – rock TBMs, drill-and-blast excavation, roadheader, NATM and slurry shield tunneling. A Team Approach to Innovation The number of innovations achieved on the ESA project could easily fill an article itself. The following is just one, but it underscores how teamwork underground can benefit everyone. One of the project’s requirements is for twin bores coming from Queens to feed eight platforms housed within two new station caverns located below the operating terminal. (see Figure 10 – alignment plan and cavern section insert). This geometric transition mandated the need for six bifurcation or “wye caverns” underground. Using drill-and-blast methods in conjunction with roadheaders, the first wye cavern took six months to complete. During the planning for this initial effort, one of HMM’s resident engineers, Ed Kennedy, recalled a technique used previously on the Chicago TARP project. Several crew members from that project working with ESA Contractor Dragados/Judlau JV, talked up the concept, and it was eventually trialed. The concept consists of the following steps:
Euclid Creek Tunnel, Cleveland The Euclid Creek Tunnel (ECT) Project is the latest element of the Northeast Ohio Regional Sewer District’s (NEORSD) $3 billion effort to dramatically reduce combined sewer overflows (CSOs) in its service area. The first deep storage tunnel to address the northeastern part of Cleveland, the 3.4-mile long, 24-ft diameter tunnel, shafts and appurtenant facilities will be used to collect, store and convey CSOs to the NEORSD’s Easterly Wastewater Treatment Plant for treatment. The subsurface conditions along the tunnel alignment will consist of thinly bedded shales and interbedded siltstone of the Chagrin shale formation. Past rock tunneling in the Cleveland area has utilized two-pass lining systems consisting of combinations of rock reinforcement and steel rib and lagging, in conjunction with a cast-in-place lining. However, a number of these projects have had to deal with the occurrence of gas, localized tunnel instability due to rock wedges and blocks, and time-related rock deformations associated with slaking, overstress or both. Because relatively high horizontal in-situ stresses are expected to exceed the rock mass’ compressive strength, spalling behavior is anticipated during tunnel excavation. Recently, the Niagara Power Tunnel endured delays and cost over-runs because the design-build team’s two-pass construction method was not able to cope with overstressed ground. To avoid similar risks on the ECT, as well as address potential gas infiltration concerns, HMM designed the ECT Project with a one-pass, bolted and gasketed lining system. Tailskin Grout System
The fast-set, two-component tailskin grouting approach has been or will be utilized on seven other HMM tunnel projects including the TYSSE, ESC and Southeast Collector projects in Toronto, the ESA tunnels in Queens, the New York Harbor Siphon Project, the Port Mann Water Main in Vancouver, and the Alaskan Way Viaduct Replacement Tunnel in Seattle. The Euclid Creek Tunnel project provides the added twist in that it will be mined with a non-pressurized TBM. Mike Vitale, HMM Project Director and Deputy Tunnels Practice Manager based in Cleveland, said: “Everyone involved understands the importance of getting the grouting right at the outset; the specs include a fairly extensive drilling and proofing program in the first 100 rings so that we get the coverage needed. McNally/Kiewit, the contractor, is also involved on our TYSSE and Port Mann projects – so lessons learned will be shared among three projects, not just one.” The following HMM staff contributed to this article: Randy Essex, Gary Kramer, Rob Dickson, David Cook, Ed Kennedy, Andy Thompson and Mike Vitale. Additional illustrations are available online at www.tunnelingonline.com. |
Comments are closed here.