To say that Deep Foundations Contractors (deep) was drilling in aconfined space within an extraction shaft on the Eglinton CrosstownLight Rail Transit Project (Crosstown) would be an understatement. Itwas the first of many challenges the firm would overcome while work-ing above and below the buzzing streets of Midtown Toronto, Canada.The epicenter of the action; however, was a 32.5 meter (107 foot) deepextraction shaft where two massive Tunnel Boring Machines (TBM)would be lifted from the ground at the end of a long subterranean jour-ney. While deep has extensive experience working in Toronto, one of North

America’s largest cities, there is nothing simple about drilling in acrowded urban environment. The Canadian powerhouse would conquerchallenges including inconsistent soil conditions, low clearance drilling,unmovable utilities, maintaining traffic flow, and darkened confinedworking spaces, in its quest to provide underground access for two rap-idly advancing TBMs.

Canada’s Largest Transit Expansion

Crosstown is a CA $8.4-billion (U.S. $6.6 billion) infrastructure pro-ject with a 19 kilometer (11.8 mile) corridor, 10 kilometers (6.2 miles) ofwhich are underground. Phase 2 includes the easternmost tunnel. Come2021, Metrolinx projects that 5,500 passengers per hour will benefitfrom this project – the largest transit expansion in Toronto history. The Phase 2 contract was awarded to the Aecon/ACS Dragados Joint

Venture (JV) in November 2013. Its scope entailed 3.25 kilometers(2.1 miles) of 6.5 meter (21 foot) diameter twin tunnels; precast con-crete tunnel lining segments; launch and retrieval shafts, headwalls as-sociated with future stations, two emergency exit buildings, three crosspassages, utility relocations, traffic staging, ground and building settle-ment monitoring, and site restoration.deep, one of Canada’s largest foundation contractors, specializes in

shoring for a wide cross-section of building and infrastructure projects.The contractor was a natural fit having worked on large transportationprojects, the most recent of which was a subway extension for theToronto Transit Commission. The Aecon/ACS Dragados JV awarded deepa roughly CA $21-million (US $16.7-million) contract to excavate andshore launch and extraction shafts for two Tunnel Boring Machines(TBM); build two emergency exits for the TBMs; and construct headwallsfor two future stations. Work started in April 2014 and concluded inMarch 2017.

To Keep the TBMs Boring

deep’s work would allow the two TBMs, known as Don and Humber,to continue their underground journey uninterrupted. The costs associ-ated with stopping their progress would be incredibly prohibitive; failurewas not an option.The Caterpillar TBMs – aptly named after two of Toronto’s rivers –

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COVER FEATUREDeep Foundations Drills

to Keep TBMs Crawling onCanada’s Largest Transit

ExpansionBy Brian M. Fraley, Fraley Construction Marketing

The BG 11 came standard with the ability to remove the upper section forlow headroom applications. ECA Canada supplied a shorter Kelly bar for theapplication.

deep Tackles Challenge of VeryConfined Space

The back and forth Foy refers to revolves around service, parts, andtraining, according to Kemppainen. “We were constantly there support-ing them with the rigs,” he said. He added that deep’s managers weregiven the unique authority to order parts directly from the jobsite, whichcomes as no surprise considering the unforgiving schedule.

Ground Conditions Present Trouble Down Below

Midtown Toronto is notorious for its troublesome ground conditions. Thisreality sunk in as deep began drilling ES-3. The first 10 meters (33 feet) included granular and silty sands. deep then hit the water tableand encountered a flowing silt, which went down 16 meters (52.5 feet). Alayer of dense glacial till stretched from 26 to 32.5 meters (85.3 to 106.6feet) below the surface. The contractor overcame the variety of soil condi-tions with careful drilling techniques and an assortment of drilling bucketsand tooling. One challenge was unstable soil. “The problem when it got wet was

the silty sand,” Foy recalled. “It was very fluid so you had to followproper procedures and techniques to make sure the drilling was consis-tent and you didn’t have any cave-ins.” deep relied primarily on BAUERdrilling buckets to conquer the material. Augers were used as a back-upand bailers helped to remove water.

began tunneling on September 30, 2015. The pair would crawl west-bound, digging 3.5 kilometers (2.2 miles) from the launch shaft at Eglin-ton and Leslie Streets before reaching their destination. The TBMs wouldeventually be hoisted out of Extraction Shaft 3 (ES-3), which sits at Yongeand Eglinton Streets, Midtown Toronto’s busiest intersection. deep’s endgoal was to prepare the shaft for their arrival.

Unleashing Canada’sLargest Fleet ofBAUER Drilling Rigs

The ace deep held in itspocket was Canada’slargest fleet of BAUER*drilling rigs. Its fleet runsthe gamut from large tosmall. In September 2016,deep purchased the BG 55from ECA. The BG 55 wasthe most powerful rotarydrilling rig on the marketat the time with 553 kNmof torque. ECA has been aleading supplier of foun-dation equipment in theEastern United States andEastern Canada for nearlya century. The contractorthen acquired one of thesmallest, a BG 11 H, in Au-gust 2017. ECA also solddeep seven Klemmdrilling rigs.

“We have the biggest fleet of BAUERs in Canada,” boasted Conor Foydeep’s Supervisor on the Crosstown. According to ECA Canada’s BranchManager Ray Kemppainen, deep geared up by purchasing five more rigsfrom late 2015 through early 2016, including a BG 46, two BG 39s, a BG40, and a BG 30.In the early 2000s, deep analyzed the drilling rig manufacturing mar-

ket and made a calculated decision to acquire BAUER drilling rigs start-ing in 2003. Analyzing the market was more about the start of arelationship than a purchase. There were no salespeople in shiny suits

with glossy brochures; the representatives from ECA andBAUER had real world drilling experience. This relation-ship between companies is equally about the people andthe equipment.Kemppainen recalls the 1970s when the firm was buy-

ing foundation equipment from his former employer, Spe-cial Construction Machines, known today as ECA Canada.deep is now ECA’s largest Canadian client. Kemppainenhas surmised after several decades of hands-on serviceto deep that it handles equipment acquisition like oper-ations: streamlined, uniform, and consistent. deep was using conventional crane-mounted drilling

equipment combined with vibratory hammers to driveand extract casing in urban environments, which is moredisruptive to residents and motorists. BAUER technologyallowed contractors to install and remove sectional cas-ings using the powerful hydraulic rotaries of the BAUERdrilling rigs. ECA was instrumental in matching equipment to the

complexities of the Crosstown, according to Foy. “Therewas a lot of back and forth,” he said. “We had to providea lot of information and work with them to get the rightequipment.” (continued on page 22) ‰

deep Contd.deep Contd.

FOUNDATION DRILLING October 2017 Page 21Page 20 FOUNDATION DRILLING October 2017

deep used a crane to lower the BAUER BG 11 H Drilling Rig into Extraction Shaft 3.

deep’s end goal was to prepare ES-3 for the arrival of two TBMs, whichwould be removed in the heart of Midtown Toronto’s busiest intersection.

The conflicting utilities in the northern half were relocatable, which alloweddeep to build a secant pile wall by drilling from the surface with one of itsfive BAUER BG 40 Drilling Rigs.

deep kept traffic flowing on Eglinton Avenue by building a temporary bridgedeck over the northern half once drilling was completed. It consisted of tim-ber mats supported by steel beams and bracing, and locked in place withSteel Angle.

of the working conditions within ES-3, adding that the mast of the BG 11H was within inches of the lowest utility support. The confined space heightwas 9.8 meters (32 feet). “You had to put in the preparation work and makesure everyone knew what they were doing and had clear procedures forwhat was happening.” The compact rig excelled at drilling in a confined space below unmovable

utilities due to its lower header configuration, according to Kemppainen.deepwas renting the rig at the time, but converted to a purchase becauseit was ideally suited for this operation. Kemppainen explained: “The BG 11 comes standard with the ability to

remove the upper section for low headroom applications. deep removedthe upper section themselves,” he said, “and ECA Canada provided ashorter Kelly bar for the low headroom application.”“The BG 11 H was the only rig that could fit under the decking and util-

ities and still be able to drill the required depth to complete that wall,” Foyexplained. “This machine was dropped in 15 meters (49.2 feet) belowground surface but it still had to drill holes from inside the shaft down an-other 17.8 meters (58.4 feet).” At 35,000 kilograms (35 tons), the BG 11 H could be safely lowered into

the excavation by a crane. The rig’s ability to deliver 110 kNm (81,130-foot-pounds) of torque down to a depth of 40 meters (131.2 feet) was a bonus.Even though the BG 11 H was compact enough to work beneath the

utilities, it was incapable of using casing to drill the remaining 17.8-meter(58.4 foot) long-piles. deep needed a high-quality, water-tight secant wallto keep the shaft dry. The contractor harnessed more than 45 years of ex-perience to develop a solution.

deep chose a polymer drilling fluid to keep the holes open. A liner wasinserted to keep the top of the excavation open and the fluid was pumpedfor the remainder of the shaft. These steps, combined with dewatering, cre-ated enough head pressure to keep the flowing silt from caving in. The slurry bubbled in the tanks at street level while being mixed and ag-

itated. deep regularly tested it for pH and viscosity before turning on theconstant flow required during drilling. Perfection was mandatory.Once the drill bit hit the founding elevation, a drilling bucket scooped

out any leftover chunks of earth. It was critical for the slurry to keep thehole open and clean while deep’s crews built sectional piles in prepara-tion for concrete pouring.

Large Piles, Confined Spaces, and Innovative Solutions

The size of the piles forced deep to improvise. At 18 meters (59 feet) inlength and 8,400 kilograms (18,400 pounds), they were too long to hoistin one piece and too heavy for the BG 11 H to lift. deep designed a hoisting device above each pile location that could

lower each of the three six-meter sections to be bolted together beforeeventually being descended to their founding elevations. The hoist couldlift three 6 meter (19.7 foot) sections together at a total weight of 8,400kilograms (18,400 pounds). Once the piles were installed to the correct el-evation the concrete needed to be placed.The concrete was placed under polymer slurry using the tremie method.

The crew poured each pile with a flexible hose connected to a sectionaltremie pipe fed by a pump that was positioned above the shaft. The pipewas then lowered to the bottom of each hole. As the concrete was placed,the slurry in each hole was displaced. deep scrutinized the volume and rateof concrete placement to guarantee that the piles were uniform and of high-quality. deep’s crews persevered 24 hours a day, six days a week to complete the

29 secant piles under a rigorous schedule. By this time the Northbound TBMhad already broken through. The Southbound TBM and a 50 person crewwere crawling quickly toward ES-3. deep had to be out of the shaft beforebreakthrough.On March 13, 2017, the lower drilling came to a successful conclusion.

Fiberglass crumbled and water spewed as the cutting head of the secondTBM, known as Don, broke through the wall of ES-3. The project was com-pleted successfully to the satisfaction of all parties involved. The close work-ing relationship between deep and the general contractor Aecon/ACSDragados JV, with some help from ECA and a fleet of BAUER drilling rigs,brought the City of Toronto about 3.5 kilometers (2.2 miles) closer to in-creased mobility.

*Indicates ADSC Members.

Conquering ES-3 – a Shaft Within a Shaft

deep’s decision during the tender process to tap Ontario-based Isher-wood Geostructural Engineers* as a shoring engineer paid off. Workingwith deep, Isherwood engineered a creative solution whereby a shaft couldbe deepened just enough to allow the BAUER BG 11 H to go below streetlevel to install a secant wall from within. After establishing the dimensionsof the rig and surveying the lowest utility supports, deep determined thatlowering the grade to 15.5 meters (50 feet) and pouring a temporary slabwould allow the BG 11 H to finish off the secant wall.

deep built ES-3in two sections:north and south.Each presented aunique set of chal-lenges. The conflicting

utilities in thenorthern half wererelocatable, whichallowed deep tobuild a secant pilewall by drillingfrom the surfacewith one of its BG40 drilling rigs.Fiberglass pilesections wereused on the east

wall to prepare for breakthrough by the TBMs. deep kept traffic flowing on Eglinton Avenue by building a temporary

bridge deck over the northern half once drilling was completed. It consistedof timber mats supported by steel beams and bracing, and locked in placewith Steel Angle.

Once utilities were surveyed, located,and protected with steel sheeting, deeprelocated its BG 40 to commence drillingin the southern half. It was important tocompare pile and utility locations toavoid any conflicts. The challenges withconfined space and drilling depths facedin the northern half remained, but allholes were completed safely and effi-ciently.Supporting utilities was deep’s top

priority when excavating the southernhalf of ES-3. The crew built a lattice ofsteel support beams to support the util-ity ducts/conduits and mains runningacross the shaft before commencingwork on the deck. Following a rigorousinspection, this deck was opened to traf-fic and the north deck was removed. Thenorth would now remain open to allowfor removal of spoils, and eventually, thetwo TBMs.deep installed an internal waler and

lagging design to continue shoring below the utilities so the slab could bepoured for the BG 11 H. The system, designed by Isherwood GeostructuralEngineers, allowed the excavation to be lowered enough for a compact airtrack drill to drive soil nails. The crew worked within a confined space to in-stall the nails and spray shotcrete in a panel sequence to keep the groundstable as excavation continued. Alternating panels allowed deep to verti-cally excavate up to 1.2 meters (4 feet) of material every week. Externaldewatering was required for the final two levels because they were belowthe water table. Most secant piles were accomplished from street-level, but three win-

dows remained in thesouthern half wherethat was not an option.Closing them during theremainder of the exca-vation proved to be thegreatest challenge ofthe complex ES-3 shaftconstruction. The client dewatered

ES-3 to lower the watertable by one meter sothe working platformcould be poured at thecorrect elevation. Theequipment ran until thesecant wall was fin-ished to keep the water at bay.

Confined Space No Problem

One of the most interesting spectacles for passersby was the sight of aBG 11 H dangling from the end of a crane line as it slowly descended belowstreet level. Drilling within the cavernous ES-3 was also one of the morecomplex engineering challenges deep overcame. “You barely had room to breathe, especially inside the shaft,” Foy said

Crosstown Project Team

Project Owner: Metrolinx

General Contractor: Aecon/Dragados Joint Venture

Shoring Contractor: Deep Foundations Contractors*

Shoring Engineer: Isherwood Geostructural Engineers*

deep Contd. deep Contd.

FOUNDATION DRILLING October 2017 Page 23Page 22 FOUNDATION DRILLING October 2017

The mast of the BG 11 H was within inches of the lowest utility support.

The cutting head of one of two tunnel boring machines is hoisted out of theextraction shaft.

It was critical for the slurry to keep the hole open andclean while deep’s crews built sectional piles in prepa-ration for concrete pouring.

deep regularly tested polymer drilling slurry forpH and viscosity before turning on the constantflow required during drilling.