前往的站在院子里,精神食粮休息aurant that has served the Crenshaw neighborhood of Los Angeles for a quarter-century, owner Gregory Dulan gestured at the unfinished rail alignment stretching along the length of Crenshaw Boulevard just yards away. In anticipation of the line’s 2019 completion, he described the renovation and expansion plans of his restaurant.

“We’re along for the ride,” he said.

The 8.5-mile, $2.1-billion light-rail line will be a new major artery in the Los Angeles Metropolitan Transportation Authority (Metro) transit system. It will link directly to two other lines—the Exposition Line and the Green Line, outside of Union Station downtown—and provide access options to the historic cultural neighborhood of Leimert Park, the future L.A. Rams stadium, downtown Inglewood, a planned museum and local businesses such as Dulan’s.

The Crenshaw-LAX Transit Project is one of 28 projects prioritized by Los Angeles Mayor Eric Garcetti (D) for completion before the 2028 Olympics. It is also one of the projects funded by a 2008 voter-passed half-cent sales-tax increase.

Building the line requires going above, below and through the busy Crenshaw corridor and will include a pair of mile-long bored tunnels, two miles of cut-and-cover tunnels, a new bridge soaring above Interstate 405 and a delicate thread through existing highway structures, linking up with the Green Line at Los Angeles International Airport. The double-tracked alignment includes eight stations, six bridges, park-and-ride facilities at three locations, utilities, landscaping, local road improvements, and a maintenance and storage facility.

沃尔什/雪茄走廊构造师的高级项目经理里克·费金斯（Rick Felkins）说：“这个项目是一项重型工作的聚宝盆。他指出，桥梁和剪裁隧道所需的广泛的虚假工作和支持系统，他说：“即使临时工程本身也很大。”

HNTB和Arup于2013年开始设计，有250人处于峰顶。HNTB设计经理Christopher Devery说：“该项目的许多部分可能是整个项目。”在设计期间，机场宣布了计划建立自动化人物制度系统的计划，这影响了Crenshaw线路的对齐。Devery说：“我们简短地进行了调整，以适应未来的第96街站连接。”他说，设计师调整了2,000英尺的轨道对准。

Under and Over

Excavation included 160,000 cu yd from tunnel boring, 385,000 cu yd of underground stations and 325,000 cu yd from cut-and-cover work.

Named for the abolitionist Harriet Tubman in local schools’ naming contest, “Harriet,” a 21.5-ft-dia tunnel-boring machine, began excavating southbound, 70 ft deep through silts and sands, in April 2016. The earth-pressure-balanced TBM, built by Herrenknecht, completed the first mile-long tunnel in October, averaging 60 ft a day. Then, crews took the 950-ton, 400-ft-long TBM apart, trucked it back to the station that will connect to the Expo Line, reassembled it and began digging the second tunnel in November. That tunnel was completed in April 2017.

The tunnels include five cross-passages at approximately 750-ft intervals that are jet-grouted due to the alluvium sands, clays and cobbles, says Matt Gallagher, director of construction management for Metro.

Tunneling went smoothly, with no major issues of settlement, groundwater or methane emissions, say project officials. Archeological issues have been minimal, as well: During station excavation last year, crews uncovered ancient bison and sloth bones about 16 ft deep, notes Gallagher. Ranging in widths from 66 ft to 125 ft, underground-station boxes are about 400 ft long—except for the Expo station, which is 800 ft to allow for crossover tracks, notes Charles Beauvoir, Metro project director. Temporary shoring for the Expo and MLK stations used cutter soil mixing, rather than beam and lagging, due to water-contamination concerns.

A mile’s worth of cut-and-cover construction in the median of Crenshaw Boulevard includes steel soldier piles and steel beams that support concrete decking for traffic. The temporary shoring work required a “tremendous” engineering effort, says Jeff Mays, WSCC senior project manager. “We installed over a thousand 70-ft-long soldier piles with businesses just 15 ft away.” The cantilevered decking system allowed crews to maintain two lanes of boulevard traffic while excavating top-down. “We were able to excavate most of the structure from the top, as opposed to hauling everything up from the bottom,” he says.

Crews also used two specialized EFCO tunnel-traveler formwork systems to pour 50-ft sections at a time in a three-day cycle. The expandable system allowed crews to pour the concrete for both the walls and the roof of the tunnel at the same time, doubling production time, Mays says.

去年五月，工作人员完成了1,510厘米，21小时的倒入，进行了3​​15英尺长的立交桥的主要跨度，该跨道将在拥挤的I-405高速公路上携带Crenshaw铁路线。随后进行了720厘米，12小时的倒入。设计建造团队修改了原始计划，该计划需要在高速公路中位数中进行新的专栏。费金斯说，现有的抛物线弹桥是现有的一座现有货运轨道，而不是拆除它的抛物线桥桥。这座旧的桥梁足够坚固，可以为新的桥支付伪造。

The pour included a complex web of pipes that pumped chilled water to cool the concrete. Supported on 11-ft-dia piers as deep as 170 ft, two columns straddling I-405 will accommodate the future widening of the freeway.

In that segment, WSCC employed deep soil mixing for mechanically stabilized earth walls to protect a 66-in.-dia, 100-year-old sewer line, which runs adjacent to the alignment; and, farther west, lightweight concrete for MSE walls to protect a 13,400-kV power line that feeds the airport.

该团队还将机场附近的以前的at级对齐更改为2,600英尺的切割隧道。Beauvoir说：“ FAA担心火车在跑道附近并引起飞行员的分心。”“他们要求我们压抑它。”当机场关闭时，工作人员使用振动桩系统在数小时内安装了700个桩。Metro副执行官金伯利·昂格（Kimberly Ong）补充说，工作人员还安装了两个500英尺的盖子，有能力处理飞机。

在该部分中，1月26日的工作人员关闭了五个绿线站，以连接Crenshaw和绿线。预计这项努力将花费大约两个月。ONG指出，对齐方式通过105号高速公路立交桥以下，最小间隙和帝国公路桥的上方。她说：“我们称其为'穿线'。”

Crenshaw-LAX项目还包括一个307美元——轧机ion, 18-acre Southwestern Yard maintenance facility for both the Green Line and Crenshaw Line trains. A joint venture of Hensel Phelps and Herzog, working under a $172-million contract, is scheduled to complete the yard this year.

Streetwise

The at-grade sections of the job required extensive coordination with multiple city agencies and businesses to minimize impact, says Mays. Other local challenges include the sheer amount of construction projects, including Metro’s Purple Line and the new Rams stadium, notes Beauvoir, adding, “It creates a big staffing challenge.”

Under its project labor agreement with WSCC, Metro is the first transit agency in the nation to adopt a “local hire” pilot program under an agreement with federal agencies. It includes a requirement that project hours be worked by 40% locally targeted workers, 10% by disadvantaged L.A. residents and 20% by apprentices.

Inspired by previous efforts in Houston, Metro also implemented a construction-mitigation pilot program for impacted small businesses. It provides up to $50,000 a year to qualified applicants; so far, Metro has paid out $6 million, says Jose Ubaldo, Metro spokesman. Metro also inaugurated two other pilot projects: a free business training and consultation service and an “eat, shop, play” campaign, wherein Metro promotes patronage of local businesses, says Ong.

In terms of context-sensitive design, the at-grade stations are among the first to use Metro’s new kit of standards for design elements, says Devery. “It is intended to bring an overall theme and consistency to Metro’s stations,” he says. “The feel of the stations is standardized in terms of the canopies, surrounding glass, the layout of the ticket vending machines, the kiosks and signage.” Local artists will be commissioned to display their work at entrances and on platforms.

Devery说：“这将使动脉变成真正的多模式走廊。”他指出，汽车和公共汽车仍将在轻轨轨道的两侧穿越Crenshaw Boulevard。“会有更大的人行道。街道和美化改善将变得美丽。最后，这将成为现有企业和未来发展的资产。”