Los Angeles Metro Red Line Segment 3 North Hollywood Extension: Trackwork Installation

Transcription

1 Los Angeles Metro Red Line Segment 3 North Hollywood Extension: Trackwork Installation By Michael J. Lehnen, P.E. Hatch Mott MacDonald (JMA C1610 Resident Engineer) ½ Bluffside Drive Studio City, CA Phone: (818) Fax: (818) and Joseph B. Valencia, P.E. Parsons Brinckerhoff (EMC C1610 Project Unit Manager) 707 Wilshire Boulevard, Suite 3300 Los Angeles, CA Phone: (213) Fax: (213)

2 AREMA Annual Conference 2001 Paper: Los Angeles Metro Red Line Segment 3 North Hollywood Extension: Trackwork Installation Authors: Michael J. Lehnen, P.E. and Joseph B. Valencia, P.E. BIOGRAPHIES: Michael J. Lehnen, P.E. is a Senior Civil Engineer with Hatch Mott MacDonald. He was the Resident Engineer for the Trackwork Installation contract on the Segment 3 - North Hollywood Extension - of the Los Angeles County MTA s underground Red Line subway system. He is currently the Resident Engineer for two other MTA contracts construction of a new bridge over the Hollywood Freeway, and the widening of an existing bridge over the Los Angeles River. Mr. Lehnen has also worked on transit, trackwork, tunneling and bridge projects in Buffalo, Boston and western Ontario, Canada. He is a licensed professional engineer in California, Colorado and New York. Joseph B. Valencia P.E. is a Senior Supervising Engineer and Professional Associate with Parsons Brinckerhoff. Currently, he is the Manager of Trackwork Engineering for the design and construction of the planned 150-mile rail rapid transit systems in Los Angeles, California. Prior to this, he worked on rapid transit projects in other parts of the country such as Baltimore, Washington D.C., Buffalo, San Francisco, San Jose. He started his engineering career with the Union Pacific Railroad Company. He is a licensed professional engineer in California, New York, Washington D.C. and Maryland. He is a member of the AREMA Committee 5 (Track) and 12 (Rail Transit).

3 Los Angeles Metro Red Line Segment 3 North Hollywood Extension: Trackwork Installation Michael J. Lehnen, P.E. and Joseph B. Valencia, P.E. ABSTRACT Contract C1610 of the Los Angeles MTA s Metro Red Line Segment 3 provided for the installation of direct fixation trackwork, including two double crossovers, in over six route miles of twin tunnels and stations from downtown Hollywood to the San Fernando Valley. A variety of track types and fasteners were utilized on this contract to suit the varying conditions along the alignment, including standard DF track, floating slabs, resiliently supported track and the use of soft Egg type fasteners, including the first installation in North America of Egg type special trackwork fasteners. The contractor utilized a plinth forming system whereby the actual running rails are set to final alignment, and the concrete placed, in one operation. This proved to be very effective and also facilitated an efficient final track surfacing operation. Also, the contractor utilized custom rail-mounted mobile batch plant vehicles for placement of concrete on the contract. This proved to be a much more expedient method than the anticipated plan to utilize drop holes located at street level. This was a fast-paced contract on the Segment 3 critical path. A major resequencing of the work was undertaken to take advantage of available work areas not anticipated during preparation of the contract. This ensured that the critical path would not be compromised and, ultimately, that Segment 3 of the Red Line would open to revenue operations on schedule.

4 Los Angeles Metro Red Line Segment 3 North Hollywood Extension: Trackwork Installation Michael J. Lehnen, P.E. and Joseph B. Valencia, P.E. INTRODUCTION Contract C1610 of the Los Angeles County Metropolitan Transportation Authority s (MTA) Metro Red Line Segment 3 North Hollywood Extension, provided for the installation of the trackwork from the current end of the operating segment at the Hollywood/Vine Station to the terminus of the Red Line at the North Hollywood Station. The contract was awarded in October of 1997 to Herzog Contracting Corporation (HCC) of St. Joseph, Missouri. The scope of work for the contract was to install direct fixation (DF) track including two double crossovers, and a tail/pocket track at the terminus in over six route miles of twin tunnels and cut and cover stations between downtown Hollywood and the San Fernando Valley. Three stations are included in Segment 3: from the aforementioned Hollywood/Vine Station, the new Segment progresses westward under Hollywood Boulevard to the first Segment 3 stop, the Hollywood/Highland Station. The alignment then curves northwestward off of Hollywood Boulevard in the vicinity of La Brea Avenue, continuing through the Santa Monica Mountains to the second stop in the Valley, at Universal City. A quick trip northward under Lankershim Boulevard and you arrive at the North Hollywood Station; the current terminus of the Red Line at the intersection of Lankershim and Chandler Boulevards.

5 Segment 1 of the Metro Red Line originates at Union Station in Los Angeles and travels through downtown to the 7 th Street/Metro Center Station. This Segment is 2.13 route miles long and began revenue operations in January of Segment 2A, from 7 th /Metro Center to Wilshire Boulevard/Western Avenue is 5.0 route miles and opened in January of 1996; and the 4.66-mile Segment 2B, from Wilshire/Vermont Avenue to Hollywood/Vine opened in June of Segment 3 opened on June 24, The Red Line provides an approximately 18-mile heavy rail subway link from downtown LA to the San Fernando Valley for the residents of Los Angeles. A schematic plan of the Red Line, along with the other MTA light rail lines, is shown in Figure 1. The designer for the C1610 contract was the Engineering Management Consultant (EMC), a joint venture of Parsons Brinckerhoff Quade and Douglas, Daniel Mann Johnson and Mendenhall, Kaiser Engineers and others. The construction manager for the contract was JMA, a joint venture of Jacobs Engineering Group, Hatch Mott MacDonald and ACG Environments and others.

6 FIGURE 1 Schematic Red Line Alignment Plan BACKGROUND AND PREPARATORY WORK The MTA had procured the major trackwork components (rail, special trackwork, direct fixation rail fasteners, contact rail and contact rail appurtenances) for the entire Red Line under earlier contracts so as to realize a cost savings from bulk procurement. This also

7 facilitated the availability of necessary material during the phased construction and operation of the system. Upon mobilizing, HCC s first task was to construct a Noise Barrier Wall around their rail welding and laydown areas adjacent to the North Hollywood Station site. This was necessary to mitigate noise and alleviate community concerns about the rail welding operation. The rail section used on the Metro Red Line is 115 RE manufactured by Bethlehem Steel Corporation. It was delivered to the rail welding site by the MTA where HCC, upon completion of the Noise Barrier Wall, welded the 80 sticks into 720 long Continuously Welded Rail (CWR) strings by the flash-butt welding process. Rail trains subsequently took these strings underground via an access ramp leading into the North Hollywood Station. The CWR strings were eventually welded together in track by the thermite welding process. TYPES OF TRACK AND DESIGN INTENT A variety of different types of track were utilized on the C1610 contract to suit the varying conditions along the alignment. They are as follows: 1. Direct Fixation w/ Standard Rail Fasteners 2. Direct Fixation w/ Standard Rail Fasteners on Floating Slabs 3. Direct Fixation w/ Soft Egg Rail Fasteners 4. Resiliently Supported Track ( Two-Block Ties in Elastomeric Boots ) 5. Special Trackwork (w/ Standard and Soft Switch Rail Fasteners)

8 Each is discussed below: 1. Direct Fixation w/ Standard Rail Fasteners This standard type of track is used in the majority of tracks including the Segment 3 trackwork. It consists of standard rail fasteners, manufactured by the Lord Corporation, along with anchor bolts and inserts, pandrol rail clips and other appurtenances as illustrated in Figure 2. The facility contractors were responsible for placement of the first pour cast-in-place invert slabs, and the C1610 contractor for the placement of the second pour concrete plinth pads, onto which the rails are fastened. FIGURE 2 Direct Fixation Track w/ Standard Rail Fastener The intent of DF track is to provide a smoother, more comfortable ride than typical tie and ballast sections, and is the common standard in underground construction. The fasteners consist of top and bottom steel plates separated by elastomeric material which

9 are bonded to the steel plates. The elastomer cushions the loads imposed by passing rail vehicles, reduces the noise and vibration and provides for electrical isolation between the rail and concrete invert. The rail is clipped to the top plate and the bottom plate is bolted onto the concrete plinth pad through the use of an insert, which is embedded into the plinth pad. 2. Direct Fixation w/ Standard Rail Fasteners on Floating Slabs In certain areas where a higher degree of noise and vibration mitigation were needed, the facility contractor was required to install floating slabs in the tunnel invert, rather than the typical cast-in-place invert slab. Floating slabs have traditionally been the preferred means of dampening noise and vibration in sensitive areas such as theaters, recording studios, churches, hospitals etc. Floating slabs were installed by the facility contractor in portions of the North Hollywood Tunnels. A typical section is shown in Figure 3. FIGURE 3 Cross Section In Floating Slab Areas

10 3. Direct Fixation w/ Soft Egg Rail Fasteners Where the need for some noise and vibration mitigation was required, but not so much as to require floating slabs, soft rail fasteners were used. These fasteners were procured under the C1610 contract, and were supplied by Advanced Track Products. A rigorous and extensive testing program was performed prior to manufacture, delivery and installation to assure compliance with the noise and vibration criteria. The use of these fasteners allowed for normal construction of the plinth pads, as opposed to the more expensive floating slabs; this resulted in a substantial cost savings to the MTA. It should be noted that currently this is only the second installation of these fasteners in the United States. The Washington Metropolitan Area Transportation Authority (WMATA) also utilizes the Soft Egg fastener. A photo showing the soft rail fasteners in track is shown in Figure 4.

11 FIGURE 4 Type 3 Soft Egg DF Fastener in Track 4. Resiliently Supported Track ( Two Block Ties in Elastomeric Boots ) As the tunnels leave Hollywood and begin heading through the Santa Monica Mountains toward the Valley, they cross the active Hollywood Fault. The tunnels were enlarged through this area, for a distance of approximately 300 feet, so as to facilitate an expedient realignment of tracks and reinstatement of train operations in the event of a major earthquake-induced ground movement. This section is known as the Special Seismic Section (SSS). The trackwork in the SSS was designed as a resiliently supported section, wherein concrete block ties, encased in an elastomeric boot, are cast into a nominal 2500 psi surrounding concrete, which is, in essence, the invert slab. The low strength concrete

12 would allow for ease of removal of the block ties and expedient realignment of the track in the event of an earthquake. The steel tie plates placed on top of the concrete ties for fastening the rail were designed and manufactured to allow 3 of lateral movement without removal of the block ties. See Figure 5 below for the typical track section in the SSS. FIGURE 5 Cross Section in the Special Seismic Section 5. Special Trackwork (w/ Standard and Soft Switch Rail Fasteners) As previously stated, there are two double crossovers in Segment 3 of the Metro Red Line. One is at the Universal City Station and the other at the terminus of the Red Line, the North Hollywood Station. Also at North Hollywood is a tail/pocket track area for storage and switching of vehicles.

13 The two double crossovers consist of four 645 radius lateral turnouts, and a 23 o diamond crossing. The tail tracks consist of two No. 10 lateral turnouts merging into a No. 8 equilateral turnout at the pocket track. All material was Authority furnished except for the fastening system of the south turnouts of the North Hollywood double crossover. This section was in an area that required noise and vibration mitigation. Therefore, the C1610 contractor was required to procure a Type 3 Special Trackwork DF Rail Fastener specifically for this application. This special fastener, the soft switch fastener or Turnout Egg, was manufactured by Clouth Gummiwerke AG of Germany, and is the first installation of its kind in North America. As with the standard soft Egg fastener, a rigorous testing program was required prior to manufacturing, delivery and installation of the fasteners. On the remaing portion of the crossover and the tail and pocket tracks, the special trackwork rail fasteners were supplied by L.B.Foster Company under a previous contract. A photo of one of the south turnouts of the North Hollywood double crossover is shown in Figure 6, and of the North Hollywood tail and pocket tracks in Figure 7.

14 FIGURE 6 North Hollywood Double Crossover on Turnout Egg Rail Fasteners FIGURE 7 North Hollywood Tail & Pocket Track Special Trackwork

15 CONTACT RAIL The Red Line is powered by contact - or 3 rd - rails energized to 750 volts DC. It rests on fiberglass rail insulators bolted (via a ferrule insert) to concrete pedestals - placed every 10 along the alignment - that is, in turn, anchored to the tunnel invert. See Figure 8 for the typical contact rail arrangement. FIGURE 8 Typical Contact Rail Mounting Insulator Section

16 The contact rail itself is an 85 lb./yd. section with aluminum cladding along the web that contributes to the ability of the rail to carry the required voltage. The 39 sections were huck bolted together in the tunnels and stations. Expansion joints were provided approximately every along the alignment to provide for any potential movement. A lubricant was also applied to the bottom of the rail and the top of the insulator for ease of any such movement. Also, anchorage assemblies were provided in the following locations to anchor the rail to both the tunnel invert and wall: a. mid-point of contact rail string, b. mid-point between expansion joints and c. mid-point between expansion joints and end approach assemblies. The anchor rods have some flexibility to facilitate any of the aforementioned movement. The end approaches are provided in various areas, most notably the special trackwork, to allow the collector plate (or shoe ) of the rail car to transition from its at rest position to the elevation of the top of the contact rail; 4 ½ above the top of the running rail. The method by which the contact rail was designed and installed in the SSS should be noted. Extended plates were installed on every fourth two-block tie, and the contact rail anchored to it. This is shown in Figure 5 above and also in the photo below.

17 FIGURE 9 Installed Track and Contact Rail in the SSS Finally, coverboards were installed as protection from the high voltage of the rail. All contact rail material was furnished by the MTA, except for the ferrule inserts and associated hardware, which were procured under the C1610 contract. CONSTRUCTION METHODOLOGY Upon being granted access to the various tunnel and station facilities, the following basic sequence of activities was performed by HCC to prosecute the work involved with the installation of the track and contact rail systems: Wash-down of the invert to provide for a clean working surface. Survey and layout of centerline of track and other necessary information.

18 Distribution and temporary anchorage of fasteners to the invert, in their final plan location. Also, distribution of reinforcing steel, formwork and Other Track Material (OTM). Distribution and placement of rail on the fasteners to create temporary track on which the next rail train, and rail mounted construction vehicles, could travel. Installation of formwork, reinforcing steel and OTM prior to concrete placement. Final survey check. Placement, finishing and curing of concrete. Removal of formwork, clean-up and relocation of operation. Patching of concrete. Final surfacing (alignment) of track. Installation of reinforcing steel, formwork and template for contact rail pedestals. Placement, finishing and curing of concrete for pedestals. Removal of formwork, clean-up and relocation of operation. Installation and huck bolting of contact rail. Final surfacing (alignment) of contact rail. Installation of expansion joints, anchors, end approaches and coverboard. Final clean-up. HCC employed a forming system developed by the Iron Horse Engineering Company named the PIP-Fast (Pour-In-Place Fastener) System for the placement of the trackwork. With this system, the actual running rails are set to final line, grade, gauge and cant on the forms; the fasteners clipped to the rail (with the inserts bolted to the fastener); and the concrete for the plinths placed in one single operation. This method proved to be much more expedient than traditional bottom up methods, whereby a template is used to position the fastener inserts prior to the placement of concrete, and

19 the final running rail subsequently installed. Since the actual rails are placed on the forms in their final position, this method also minimized the need for shims during the final surfacing of the track. The steps in this system were to remove the fasteners from the existing invert and place them, along with the rails, onto the form in their final location; temporarily bolt the insert to the fastener; install the rebar and side forms; perform a final survey check and place the concrete. Shown in Figure 10 below are the PIP-Fast forms supporting the running rail and fastener assemblies prior to the placement of the outside forms and concrete.

20 FIGURE 10 PIP-Fast Forms and Track Prior to Concrete Placement Concrete placement was facilitated by HCC s innovative use of a mobile batch plant manufactured by Zimmerman Industries ( Zimm Mixer ). HCC purchased two of these units for the C1610 contract and had them retrofitted with hi-rail equipment so that they could be utilized on track. The Zimm Mixer has compartments for the various concrete components (fine and coarse aggregate, cement, water and admixture), and is batched and dispatched at the required locations. A standard 4000 psi mix design was developed and tested for use on the contract. Trial batches were made with the Zimm Mixer in the laydown area; then tested and refined until a suitable strength and consistency was arrived at. The final mix included a water

21 reducer added to enhance workability. Final strengths of the cylinder breaks for the project averaged well into the high 5000 psi range. Almost all of the concrete placed on the project was done so using the Zimm Mixers. The trucks would be loaded with the components in the laydown area, and driven into the various facilities (via the aforementioned North Hollywood access ramp), batched at the pour location and pumped to the point of discharge in the plinths. This method proved to be much more expedient than the original plan, which was to utilize drop holes, located along the Segment 3 alignment at street level. This would have required traffic controls and would have resulted in a much more expensive and time-consuming operation. The trucks held enough of the various components to produce approximately 11 cubic yards of concrete. This equated to approximately 600 track feet of plinth pads, which FIGURE 11 Zimm Mixer on North Hollywood Access Ramp (Note Hi-Rail Gear)

22 was HCC s average daily production. A photo of the Zimm Mixer is shown in Figure 11. EXECUTION OF THE WORK The critical path for the overall Segment 3 project ran directly through the C1610 contract. It was a fast-track contract, with the various Systems contractors (Automatic Train Control, Traction Power, Communications, etc.) following closely behind as the trackwork was completed. HCC forces worked 24 hours per day, six days a week during the prosecution of the majority of the work. Access to the various tunnel and station facilities was phased to allow for proper sequencing and coordination of the work within the overall Segment 3 schedule. The C1610 contract schedule was developed so that the trackwork installation would proceed from north to south, with the contractor completing the work in one facility prior to being granted access to the next. The Segment 3 facility contracts, from north to south, are as listed below: North Hollywood Station (Contract C0351) North Hollywood Tunnels (Contract C0331) Universal City Station (Contract C0321) Hollywood / Santa Monica Mountains Tunnels (Contract C0311) Hollywood/Highland Station and Tunnels (Contract C0301)

23 During installation of the track in the C0331 tunnels, it became apparent that the difficult C0311 tunnels through the mountains would not be available at the time originally anticipated during development of the C1610 contract schedule. Therefore, the C1610 work was resequenced to take advantage of the availability of the C0301 station and tunnels, which were already finished to the point where they were ready to accept track. After completion of the work in the C0321 station, HCC redirected their efforts south to Hollywood. This presented a logistical problem, as there was no longer direct access from the staging area in North Hollywood to the C0301 station area the tunnels linking the two were still being completed. Therefore, HCC was required to access their new work area through the operating portion of the Red Line, from Union Station in downtown Los Angeles to the Hollywood/Vine Station. This meant that all work had to be performed at night, after revenue operations were completed for the day. Further complicating the matter was the fact that the Zimm Mixers would not clear the installed facilities in the operating portion of the system, and therefore could not be utilized for this portion of the work. To circumvent this problem, HCC mounted a motorized lo-railer vehicle with a concrete drum mixer and brought this new piece of equipment into their work area through the operating segment. This lo-railer was stored in the tunnels and did not have to be removed on a daily basis, which reduced trips into and out of the operating segment. However, all rail and other material still had to be delivered from Union Station. For supply of concrete, HCC cycled the Zimm Mixers from their laydown area in North Hollywood to the La Brea Shaft site. These shafts were installed by the tunnel

24 contractor and are approximately 32 in diameter. They are located on a site off of La Brea Avenue in Hollywood and descend over 100 to each of the two tunnels below. The Zimm Mixers batched the concrete into a pump, and it was pumped down one of the shafts into the awaiting lo-railer drum. A second pump was placed at the work area, and the lo-railer, essentially a concrete truck, was driven to it with a full load of concrete. Although a complex operation, the learning curve was short and the end result was successful. HCC then remobilized back north to finish the work in the C0311 tunnels. This was no easy task, as these tunnels were the longest stretch of the project (at three miles each) and, due to the large hydrostatic head under the mountains, were not designed to be waterproof, as were the other Segment 3 tunnels. Therefore, standing (and in some cases flowing) water on the invert presented problems throughout all phases of the operation. These problems were overcome, and HCC eventually completed all contract work on time and well within budget. All interim milestones were met, which meant that the systems contractors could gain their access on time and the project would remain on schedule. PARTNERING A point that must be mentioned when discussing the C1610 contract is the enormous success of the Partnering Program.

25 A formal, two-day facilitated session was held during the early stages of the contract, with subsequent monthly meetings. Representatives of the Owner, Contractor, Designer and Construction Manager all attended these meetings, and discussed progress on goals set both during the initial session and the previous month. However, the success of the program went beyond monthly meetings. All involved parties put a serious commitment towards the program, and it resulted in a true team spirit pervasive throughout the project. All truly did come together as a team to work towards the successful completion of a common goal. CONCLUSION Through the hard work and use of innovative ideas proposed by the contractor, the flexibility of the Owner, Designer and Construction Manager, tight quality control and inspection measures and a successful Partnering Program, the critical path trackwork installation contract was completed on time and well within budget. This ensured that the systems follow-on work could proceed as scheduled and ultimately, that Segment 3 of the Los Angeles County MTA s Red Line was prepared for revenue operations as planned.

26 ACKNOWLEDGEMENTS The Authors wish to acknowledge the Los Angeles County Metropolitan Transportation Authority and Herzog Contracting Corporation for allowing us to present the information contained in this paper.