Tunnel Business Magazine

AUG 2018

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Page 27 of 43

TUNNELINGONLINE.COM TBM: TUNNEL BUSINESS MAGAZINE // AUGUST 2018 eas were easily custom fit by a carpenter crew electrical utility conduits were relocated on the side walls of the tunnel as a part of the electrical and communication upgrade package. New Midtown Immersed Tunnel Fire Protection System The contract documents f unnel specified a fire board protection system. Spray fire protection was not allowed as the owner required the fire protection to be easily removed for inspection on a routine basis, especially considering the fact that is an underwater immersed tunnel. The contractor explored two options of means and methods of installation – "Lost Formwork" method and the "Post Fixed" method. "Lost Formwork" method is the place- ment of fire protection boards on top of the concrete formwork, simply butt joint- ed. After the boards are in place, stainless steel 316 deck screws – 0.25 x 2 in. – are inserted into the back side of the board for additional concrete anchorage. Once the boards are in place on the concrete forms, the reinforcement steel is installed and concrete cast in place. After the concrete cures, the forms are removed, and the fire protection boards are in plac of forms or demolding grease is required. There is a chemical bond between the boards and tunnel structure during the curing process, but experience has found that it is not reliably consistent, thus the requirement of the stainless steel deck screws for additional anchorage. The Lost Formwork method is a simple and quick method for installing fire pro- tection boards on a rectangular tunnel sections or cut-and-cover sections. How- ever, the chemical bond and anchors on the back side of the board combine to make removal of the fire protection diffi- cult. For this reason, the Post Fixed meth- od was chosen. The contractor/designer chose to use calcium silicate boards specifically used for immersed tunnels. The thickness re- quirement is 27.5 mm to meet the 2-hour RWS time/temperature curve. The initial design was to fire protect the ceiling and 1 m down the side walls. These fire protec- tions boards are butt jointed and placed di- rectly against the concrete. The standard board format for this type of board is 1,250 x 2,500 mm and weighs 168 lbs. To facili- tate ease of handling, the contractor chose to use half size boards, 1,250 x 1,250 mm and weighing 84 lbs. These boards were anchored using 9 each 0.25 x 3.25 in. me- chanical expansion anchor with nut, ny- lon insert and 30 mm (1.125 in.) washers, all 316 stainless steel. The initial design did not have fire pro- tection on the walls. During the design process, the design team decided to add additional fire protection on the walls. For the walls, the team chose a different type of board. The board chosen was a cal- cium silicate aluminate matrix engineered board, 22 mm thickness, in a half board format (1,200 x 1,250 mm). These boards were also anchored direct post fixed to the concrete surface with 9 each 0.25 x 3.25 in. mechanical expansion anchor with nut, nylon insert and 30 mm (1.125 in.) wash- ers, all 316 stainless steel. Since these boards are in the reflective zone, they were pre-coated: three coats front side and two coats back side. The col- or was an off-white two-part water-based epoxy coating to facilitate mechanically washing the fire protection panels on a routine basis. The top coating also increas- es the light reflection in the tunnel. Thermal Justification of the System As in the existing tunnels, test data pro- vided sufficient thermal information on system performance of the proposed sys- tem along with calculation to comply with the requir A 502-2011. As in the existing tunnels, the fire pro- tection system was fire tested to 2-hour RWS time/temperature curve to confirm the thermal performance. Experiences New Midtown Immersed Tunnel To secure the transverse mechanical metal framework to the ceiling, stainless steel mechanical struts were cast in the ceiling slab running longitudinally to the tunnel alignment. To install the mechani- cal metal framework, a 3-in. circular coupon was removed, exposing the em- bedded mechanical struts. Half-inch di- ameter stainless steel hanging rods were installed in to the exposed mechanical strut to hang the mechanical framework. A 6 x 6-in. cover piece of 22 mm fire pro- tection board covered the exposed area in the ceiling. This cover ensured the in- terface temperature did not exceed 380 C. This cover was held in place with a stain- less steel lock nut and washer. A thermal simulation for the connec- tion of the hanging rods and mechanical strut was prepared by PRTC (Promat Re- search Technology Center) to determine the thickness required to thermally pro- tect the concrete tunnel substrate and lim- it the heat sink into the metal strut. Based on the testing, the conclusion was that the concrete temperature is not negatively in- fluenced by the strut-rod-connection. 2 8 In 2012, Hurricane Sandy devastated the York City metropolitan area. Sandy's impact included major flooding of all highway tunnels except the Lincoln Tunnel. Among those flooded was the Hugh L. Carey Tunnel (formerly known as the Brooklyn-Battery Tunnel), which crosses under the East River connecting ttan and Brooklyn. The brackish floodwaters affected all tunnel services, req d repairs to the concrete liner, ceiling slab dividing the roadway and the ventilation plenum, air ducts, tunnel wall tiles, ceiling finishes, LED lighting, traffic control communica- tion, CCTV, fiber-optics, lead and asbestos abatement, and upgrade fire-life safety to A 502. The project was delivered by design-bid-build method. History of Hugh L. Carey Tunnel The Hugh L Carey Tunnel opened on y 25, 1950, and is 9,117 ft long, mak- ing it the longest continuous underwa- ter vehicular tunnel The first month of operation the tunnel carried approximately 41,000 vehicles. Today, traffic averages over 60,000 vehi- cles per day. The tunnel consists of twin- unidirectional roadways with transverse ventilation beneath the East River con- necting via Governor's Island. Restoration of the Hugh L. Carey Tunnel

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