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TBMs continue metro success in Los Angeles 03 Aug 2017

Herrenknecht News Release

As well as being a bustling metropolis above ground, the area below ground in Los Angeles is busy with the construction of new metro transit routes. The twin running tunnels for the underground sections of these new lines are being excavated by six Herrenknecht TBMs. .

A total of six TBMs will work on the current metro rail extension
A total of six TBMs will work on the current metro rail extension

The first TBM of these six to action completed its parallel 1.6km long drives for the new Crenshaw to LAX Line in April. The second machine is working on the Regional Connector project and finished excavating the first of its twin 1.7km long tunnels on 18 July. From Spring 2018 two further new Herrenknecht TBMs will join the metro project for the drives through difficult ground on the Purple Line Extension Sections 1 and a further two machines are on order for the Purple Line Extension Section 2. All three projects are part of 14km of strategic subway extension to relieve traffic congestion in what is recognised as the car-capital of the world.

The Crenshaw/LAX line will improve public transit connections to the Los Angeles International Airport (LAX). Passenger numbers through the airport are on the rise from more than 80 million in 2016.

TBM 1. Crenshaw/LAX Line
Contractor: Walsh/Shea JV with design firm HNTB
Machine: 6.5m diameter EPBM
Drive power: 1,512kW
Tunnel length: 2 drives x 1.6km
Geology: Alluvium, fine to medium grain sand and gravel, stones and blocks, silts and clays

The Herrenknecht TBM working on the line excavated its first drive, between the future stations of Expo/Crenshaw and Leimert Park, before being transported back to the launch shaft for the second parallel drive and broke through to complete the drive in April 2017. With a best performance of 43m in 24 hours and 170m for the best week, it set a new record in mechanized tunnelling with a subway sized EPBM for the city of Los Angeles. The new Crenshaw/LAX line is expected to open on schedule in 2019.

TBM completes 3.2km Crenshaw Line drive
TBM completes 3.2km Crenshaw Line drive
TBM is explosion protected for work in the gaseous soils
TBM is explosion protected for work in the gaseous soils

The Regional Connector TBM started its first 1.7km drive in February of this year and broke through at the 4th Street reception shaft in July. It will now excavate the parallel tunnel towards a final breakthrough scheduled for the end of this year.

A Regional Connector  breakthrough
A Regional Connector breakthrough

TBM 2. Regional Connector link
Contractor: Skanska/Traylor Bros JV
Machine: 6.5m diameter EPBM
Drive power: 945kW
Tunnel length: 2 drives x 1.7km
Geology: Weathered siltstone and claystones, sands, gravel, stones and boulders

One of the greatest challenges for tunneling projects under Los Angeles is the gassy geology Contracting JVs looked to Herrenknecht for specialist technology to navigate the gaseous conditions safely. Electrical components in the TBMs are explosion-protected and will excavate the complex geological conditions beneath the inner city densely populated areas with the highest degree of safety.

Designers and engineers at Herrenknecht are now preparing the four new TBMs that will join the project in Spring 2018 and Spring 2019 to work on the Purple Line extension contracts. A decade ago, two Herrenknecht EPBMs excavated 4km of running tunnels for the underground section of the Gold Line into East Los Angeles.

The current EPBM machine performances and with the four TBMs to arrive in Los Angeles for the Purple Line will add to a story of ongoing success.

Gold Line achievement in 2006
Gold Line achievement in 2006

TBMs 3 and 4. Purple Line Extension Section 1
Contractor: Skanska/Traylor/Shea JV
Machines: 2 new 6.6m diamater EPBMs
Drive power: 945 kW
Tunnel length: 2 drives of 5.25km
Geology: Sands, silt, stones and boulders, slightly weathered siltstone and claystones

TBMs 5 and 6. Purple Line Extension Section 2
Contractor: Tutor Perini/O&G JV
Machines: 2 6.62km EPBMs
Drive power: 945 kW
Tunnel length: 2 drives x 3.2km
Geology: Sands, silt, stones, boulders, slightly weathered siltstone and claystones

References

           

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