Archives: Projects

The Niagara Tunnel Project

Project Overview

The Niagara Tunnel Project is an ambitious project to tunnel 10.4 km (6.5 mi) from the Sir Adam Beck Generating Complex to above Niagara Falls. The new tunnel will increase the power supply for owner Ontario Power Generation (OPG) by 150 MW and will help to bolster the current power system, which is close to exceeding its capacity during peak months.

OPG awarded the construction contract to Austria-based Strabag AG, who chose a 14.4 m (47.5 ft) diameter Robbins Main Beam TBM to bore the tunnel. The setup included a 105 m (345 ft) long back-up system, which transported 1.7 million m³ (2.2 million cubic yards) of muck over three years via conveyor belt.

Geology

The tunnel is located predominantly in Queenston shale with some limestone, dolostone, sandstone and mudstone up to 200 MPa (29 ksi) UCS. The rock along the tunnel bore path is known to have high in-situ stress and there is potential for squeezing ground. An initial rock support lining of wire mesh, steel ribs, rock bolts, and shotcrete was installed as the TBM advanced. Behind the excavation, an in-situ placed concrete lining is being installed. The final lining will include a waterproofing membrane system to ensure that water does not seep from the tunnel into the rock and cause swelling.

TBM

The Main Beam TBM, the largest hard rock TBM in the world, was assembled at the jobsite using Onsite First Time Assembly (OFTA) in less than 12 months — ahead of a tight delivery schedule. The onsite assembly is considered unprecedented for such a large TBM. The TBM began boring in September 2006.

The Main Beam TBM was also the first ever to utilize back-loading 20-inch cutters, which increase cutter life and reduce cutter changes in hard rock. Both 19-inch and 20-inch cutters could be installed in the cutterhead. The machine had a cutterhead thrust of 18,462 kN (4,150,422 lb) and a maximum torque of 18,670,000 N-m (13,770,285 lb-ft).

Tunnel Excavation and World Records

After about 793 m (2,600 ft) of excavation the TBM entered the Queenston shale formation, where large rock blocks started to fall from the crown before rock support could be placed. In some cases, significant over-break up to 3 m (10 ft) above the cutterhead support was reported.

Strabag ultimately designed a unique ground support system to cope with the geology, which consisted of 9 m (30 ft) long pipe spiles in an umbrella pattern at the crown of the tunnel. Using the new spiling method, over-break was limited to about 0.9 m (3 ft) above the normal tunnel diameter. Nearly 500 m (1,640 ft) of very difficult ground was excavated using this method, at average rates of about 3 m (10 ft) per day.

The new ground support program, done for all excavated ground, consisted of 3 to 4 m (10 to 13 ft) long rock bolts, self-drilling (IBO) anchor bolts, steel straps, wire mesh and wire-reinforced shotcrete. Crews typically bored half a stroke, then began scaling down loose rock and installing rock bolts. After the full 6 ft stroke, the rest of the loose rock was scaled down before installing more rock bolts, wire mesh, steel straps and a layer of shotcrete.

OPG and the contractor also opted to alter the vertical alignment of the tunnel, raising it 46 m (150 ft) to move the tunnel out of the Queenston shale. After 1,981 m (6,500 ft), rock conditions were competent enough that spiling was no longer required.

After surpassing these challenging rock conditions, the machine achieved a world record-breaking month for any TBM 11 m (36 ft) in diameter or larger. During July 2009, the TBM excavated 468 m (1,500 ft) in one month and advanced 153 m (503 ft) in one week overcoming significant geological challenges.

Breakthrough

May 13, 2011 marked the completion of the TBM’s drive.  A well-attended ceremony celebrated the final breakthrough of the 14.4 m (47.2 ft) diameter Robbins Main Beam, following advance into a 300 m (1,000ft) long grout tunnel on March 1, 2011.

While the tunneling portion of the project has reached completion, two years of work still remain. Approximately 30% of the continuous concrete lining was completed during tunneling, with about two thirds of the work still to be done. The finished 12.8 m (42 ft) diameter tunnel will be fully lined with both 600 mm (24 in) thick cast in place concrete and a polyolefin waterproof membrane to prevent leakage. Other construction remaining includes the outlet structure, gates, and removal of the cofferdam in the Niagara River, as well as removal of the rock plug at the outlet end.

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Línea 12 del Metro de México D.F.

Descripción del proyecto

El sistema de Metro de México D.F. es uno de los más extensos del mundo, con más de 200 km de vía instalada y transportando a cerca de 4 millones de pasajeros al día. La nueva línea, de 25,4 km de longitud, atraviesa 22 estaciones nuevas entre los barrios de Tlahuac y Mixcoac. El nuevo túnel de 7.7 km representa la primera nueva ruta en la capital en más de diez años y dará servicio a miles de pasajeros diariamente.

En 2007, el Distrito Federal hizo público su plan de construir la línea 12 del metro de México D.F. El Consorcio ICA, adjudicatario de la obras, encargó a Robbins la fabricación de una tuneladora EPB de 10,2 m de diámetro, de su back-up y de las herramientas de corte necesarias. La TBM es la más grande que ha trabajado nunca en México y fue la primera tuneladora en la historia de Robbins que se acogió al plan de Primer Montaje en Obra (OFTA, en siglas inglesas). La geología a atravesar en esta línea de metro consiste en capas de arcillas, arena y bolos rocosos de hasta 800 mm de diámetro, dado que la zona corresponde a parte del antiguo lecho de un lago. Las condiciones de terreno bajo México D.F. son verdaderamente especiales y se precisó un programa muy detallado de control de las vibraciones debidas a la perforación.

La gigantesca tuneladora va equipada con un transportador de tornillo sinfín de tipo de guirnalda, de dos etapas, 1200 mm de diámetro, seguido por otro sinfín de tipo de eje,  especialmente diseñados para gestionar la evacuación e bolos rocosos de gran tamaño. En ciertas zonas del túnel en las que se atravesaban arcillas muy blandas con alto contenido en agua, el escombro se evacuó utilizando bombas de lodos, en  lugar de cintas o vagones de escombro. La máquina también disponía de articulación active para evitar las deformaciones de los anillos de dovelas instalados en curvas tan cerradas como de 250 m de radio. La cabeza de corte, de tipo de brazos radiales, llevaba útiles de corte afilados de carburo de tungsteno para mayor eficacia en el corte de terrenos blandos. Los asentamientos del terreno se controlaron mediante el uso de aditivos y de inyecciones de dos líquidos en el trasdós de las dovelas. Las inyecciones de dos líquidos, cemento y acelerante, se endurecen con rapidez y eliminan la necesidad de usar bombas de hormigón de alta presión que pueden ocasionar perturbaciones al terreno. La máquina revestía el túnel mientras avanzaba, instalando un anillo universal de 7+1 dovelas de 400 mm de espesor.

La EPB Robbins arrancó el 15 de febrero de 2010 tras solamente ocho semanas de montaje. El pozo de ataque, de unos 34 m de longitud, 14 de anchura y 17 de profundidad, estaba situado en una de las zonas más densamente pobladas de la ciudad. Dadas las pequeñas dimensiones del pozo, la máquina perforó sus primeros 70 m accionada remotamente desde los remolques del back-up todavía en superficie. Los remolques se fueron arriando y añadiendo al equipo según la máquina avanzaba.

La mayor parte del túnel  discurrió bajo coberturas tan escasas como 7,5 m, por lo que se precisó un control muy fino de los asentamientos del terreno. La situación del túnel en pleno centro urbano implicaba la proximidad de un buen número de estructuras de construcción anterior. La máquina pasó a solo 1,5 m de un colector de 4 m de diámetro, a 2 m de cimentaciones de edificios y a únicamente 3,5 m por debajo de las líneas activas de metro 2 y 3. La máquina alcanzó su primera estación en abril de 2010 tras perforar 495 m de túnel. Las mayores dificultades se encontraron en las tuberías de lodos pero, después de ser rediseñado, el sistema funcionó de manera excepcionalmente buena. Desde ese punto, la EPB atravesó seis estaciones más en cada una de las cuales se le practicó un mantenimiento rutinario. El 1 de marzo de 2012 la máquina complete con éxito la totalidad del túnel.

A su terminación, la línea 12 del metro de México D.F. es la más larga de todo el sistema. Esta nueva línea se estima que transportará una media de 367.000 pasajeros al día, alcanzando así el cuarto lugar en cuanto a las rutas de tránsito sobre vía más frecuentadas en la capital.

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Mejoras sanitarias en Locust Street, proyecto No. 6335

Descripción del proyecto

El contratista general Northwest Earthmovers Inc. ha construido más de 1,8 km de colectores por gravedad en la ciudad de Tigard, Oregón para la propietaria del proyecto Clean Water Services. La empresa Gonzales Boring & Tunneling fue subcontratada para la perforación de tres galerías, que formaban parte del proyecto nº 6335 de mejoras sanitarias en la calle Locust, de 70, 183 y 98 m de longitud respectivamente. La tubería a instalar, de 450 mm de diámetro, está destinada a incrementar laas capacidades de gestión de aguas residuales en la zona así como para evitar inundaciones.

Gonzales Boring & Tunneling adquirió una SBU-A Robbins de 1,0 m de diámetro para perforar las tres galerías que atravesaban las calles del vecindario, sus viviendas, un pequeño arroyo y una fábrica.

Geología

La primera galería se situaba en terrenos de arcilla y basalto, mientras que la segunda atravesaba basaltos de resistencias entre 48 y 82 MPa. En algunas zonas se encontró arena y pequeños bloques de roca.

Características de la SBU-A

Las cabezas de corte Robbins SBU pueden equiparse con picas de carburo de tungsteno y cortadores de disco, sencillos o de varios discos, dependiendo de las condiciones del terreno a perforar. A la que nos ocupa se le montaron cortadores de disco simple de 6,5” de diámetro y se sobredimensionaron alas aberturas de evacuación de escombro a la vista de los terrenos mixtos a excavar.

Para arrancar se soldó la SBU-A a una tubería guía de acero. El empuje y par necesarios para el avance de la cabeza se lo proporcionó una perforadora de tornillo sinfín (ABM). Los cangilones de la cabeza recogían el escombro volteándolo al transportador sinfín para su evacuación al exterior.

Excavación del túnel

Bajo un estricto  control de la alineación de la perforación por parte del personal del contratista, la máquina avanzó sostenidamente en índices de 12 m por turno de 10 h. El sistema de guiado ideado por el contratista permitió que la máquina calase con una desviación de solo una centésima de pulgada sobre su objetivo tras 183 m de excavación. Además de establecer un record de longitud en una única perforación, la máquina no necesitó reemplazar ni un solo cortador en 250 m de túnel. La máquina perforó una tercera galería del proyecto  de 98 m de longitud a comienzos de 2010.

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Dahuofang Water Tunnel

Project Overview

The Dahuofang Water Tunnel is a large reservoir diversion project that will transport water from high rainfall areas to the dry, heavily industrialized Shenyang region of China. The total length of the tunnel is 85.3 km (53 mi) with over 60 km (37 mi) being driven by tunnel boring machines (TBM) — one of the world’s longest TBM-driven tunnels.

Geology

The project owners awarded construction contracts in three lots, each about 20 km (12 mi) long. Lot 1, awarded to Beijing Vibroflotation Engineering Co Ltd, chose an 8.03 m (26.3 ft) diameter Robbins Main Beam TBM for the project. The machine is responsible for a 20 km (12 mi) bore in migmatite and orthopyre geology.

The Lot 3 contract was awarded to The Bureau of Water Conservancy and Hydroelectric Power Construction, who chose a nearly identical 8.03 m (26.3 ft) diameter Robbins Main Beam TBM for a 16 km (10 mi) long bore. This section of tunnel also passes through migmatite geology, but about two-thirds of the tunnel contains a complex mixture of heavily weathered and fractured rock.

TBMs

Both Robbins Machines include forty-three 19 in (483 mm) cutters and eight 17 in (432 mm) center cutters. The cutters are backloading with frontloading optional. Both machines use variable frequency drive systems and can generate a maximum thrust of 22,934 kN (5,155,767 lb) and the cutterheads of both machines have a torque of up to 6,275,000 N-m (4,628,202 lb-ft).

Robbins also provided the back-up systems for both machines. Each back-up includes a bridge conveyor, transfer conveyor, track-laying area, and rolling gantries among its units. The TBMs use slightly different conveyor systems — the conveyor for TBM 3 is a shorter length with a consequently reduced power-drive system.

The TBM accessory equipment mounts included probe drills and rock bolting systems, which are compact for working in limited space.

Tunnel Excavation

The Robbins TBMs began boring in June and July of 2005. In March of 2006, after only 8 months of boring, TBMs 1 and 3 had advanced 3.8 and 4.0 km (2.4 and 2.5 mi), respectively. The TBMs completed tunneling in 2007.

 

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The Manapouri Hydroelectric Project

Project Overview

The Manapouri Hydropower Station is the largest hydropower station in the country and supplies 5100 GWh of electricity annually. In 1997, the project owners, Electricity Corporation of New Zealand (ECNZ), proposed an expansion of the hydropower station from its then output of 585 MW. The plan included a second 9.6 km (6.0 mi) long tailrace tunnel connecting the underground power station at Lake Manapouri to its discharge point in Doubtful Sound.

In 1997 ECNZ awarded the construction contract, worth US $85 million, to a Joint Venture of Fletcher Construction (New Zealand), Dillingham Construction (U.S.), and Ilbau (Austria). The joint venture awarded the contract to Robbins for one 10.05 m (33.0 ft) diameter Main Beam TBM to excavate the tunnel.

Geology

The tunnel passed through Paleozoic metamorphic and igneous rocks. The metamorphic rocks included gneiss, calcsilicate, quartzite, and intrusions of gabbro and diorite. The tunnel geology also included five sub-vertical fault zones with high potential for water inflows.

TBM

Robbins designed the 10.05 m (33.0 ft) diameter TBM for the mixed face hard rock conditions in the tunnel. The Robbins design was then built by Kvaerner-Markham (U.K.) and shipped to the job site. The cutterhead featured sixty-eight 17 inch (432 mm) cutters with loading from either the front or back. Eleven two-speed electric motors powered the cutterhead with 3,463 kW (4,642 hp), generating a torque of 9,859,400 N-m (7,271,919 lb-ft). The 470 m (1,542 ft) long back-up system, built by Rowa Engineering, included a secondary rock-bolting station and a robotic shotcrete station.

Tunnel Excavation

The Robbins TBM began boring in June 1998 and finished in 33 months. The tunnel progress was divided into four sections, or reaches. During Reach 1, about 1.8 km (1.1 mi) into the bore, the machine experienced few problems. During Reach 2 (spanning 2.4 km (1.5 mi)), the machine encountered heavy water inflows through the fault lines. These inflows reached proportions of 1,300 liters (343 gallons) per second and pressures up to 7.2 MPa (1.0 ksi). These high volumes of inflow necessarily slowed progress throughout Reach 2. Geological conditions improved in Reach 3 (spanning 2 km (1.2 mi)), and by Reach 4 (spanning the final 3.2 km (2.0 mi)) the machine was progressing at a substantial rate.

Despite setbacks due to water, the Robbins TBM suffered no major breakdowns and availability remained high throughout the dig. In addition, total TBM spare parts usage was far below the industry average for this type of job.

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Kárahnjúkar Hydropower Project

Project Overview

The Kárahnjúkar Hydropower Project created the Kárahnjúkar Power Plant to provide 4600 GWh of electricity annually to a nearby aluminum smelting plant. Three dams feed the main Hálslón reservoir and several other dams join the outflow in a combined headrace tunnel to an intake. The intake water travels to the powerhouse through two steel-line vertical shafts and exits from a tailrace tunnel that empties into the Jökulsá i Fljótsdal River.

Project owner Landsvirkjun awarded the construction contract for the hydroelectric project to the Iceland branch of Impregilo S.p.A. The contractor awarded the contract to Robbins for three Robbins Main Beam High Performance TBMs for three lengths of tunnel.

Geology

The machines began boring between April and September 2004 in basalt, moberg, and pillow lava geology up to 300 Mpa (44,000 psi) UCS. A number of fault lines and water inflows were encountered during boring, though the machines made good progress.

TBMs

All three TBMs were the first ever machines designed with back-loading cutterheadsfor 19” cutters. The successful design increased cutter life and reduced the time needed for cutter changes. All of the TBMs were equipped with probe and roof drilling capabilities and were specially designed for the ground conditions. The cutterhead designs featured rock deflectors to protect the cutterhead from fractured and blocky ground, as well as abrasion-resistant wear plates and carbide buttons to bore in abrasive rock.

Tunnel Excavation

Main Headrace Tunnel
By June 2006 the machines had made good progress despite difficult geologic conditions in the tunnels. TBM 1 finished its drive on September 9, 2006 after achieving impressive advance rates with a best month of 864.6 m (2,755 ft) in March 2006. On the same day, TBM 2 tied a world record in its size class after excavating 92 m (302 ft) in 24 hours. The TBM tied the record with another TBM that bored on the Epping to Chatswood Rail Link. TBM 2 finished its initial drive in Fall 2006 and was then disassembled and transported to bore an additional 8.7 km (5.4 mi) long section of the Jökulsá Diversion Tunnel in 2007. The third TBM finished its main tunnel drive on December 5, 2006. All of the TBMs achieved impressive monthly advance rates despite troublesome rock conditions.

Jökulsá Diversion Tunnel
The Jökulsá Diversion Tunnel adds to the water supply capacity of the powerhouse by connecting the Ufsarlón Reservoir to the main headrace tunnel. Work began in April 2007 and finished in April 2008. During the 8.7 km (5.4 mi) drive, TBM 2 continuously turned in record-breaking performances, beating its own record in June 2007 by excavating 106.1 m (348.2 ft) in 24 hours.

In August 2007, the machine achieved the feat again by excavating 115.7 m (380 ft) in 24 hours and 428.8 m (1,400 ft) in one week. The machine excavated at consistently high rates and finished its bore on schedule.

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The Channel Tunnel

Project Overview

The Channel Tunnel, one of the world’s most famous tunnels, is a 50 km (31 mi) tunnel under the English Channel linking Great Britain to France. This link consists of three parallel tunnels running for 39 km (24.2 mi) under the sea. Two Main Rail Tunnels, about 30 m (98 ft) apart, carry trains from the north and from the south. In between the two tunnels is the Channel Service Tunnel, which is connected by cross-passages to the main tunnels. This service tunnel allows maintenance workers to access the rail tunnels at regular intervals.

The contractor for the project, Transmanche-Link (TML) chose five Robbins TBMs to participate in boring the crossings. TBMs were deployed at both the U.K. and France Terminals.

Geology

The majority of the Channel Tunnel passes through chalk marl, much of it faulted. Below the Chalk Marl is a thin 2 m (6.5 ft) band of permeable Glauconitic Marl. This rock is a weak sandstone with a stronger rock strength than the Chalk. The bottom of the tunnels pass through stiff clay with some swelling characteristics. The Chalk is much more faulted and prone to water inflows on the French side of the tunnels.

TBMs

Robbins built five machines for this project, each designed for the geology of a specific length of tunnel.

The high water pressures predicted in the folded and faulted chalk on the French side required the use of three Earth Pressure Balance machines (EPBMs). These machines featured sealed cutter chambers to withstand high water pressures and screw conveyors to carry the cut material from the face.

Robbins built two EPBMs for the French side of each Main Rail Tunnel. These 1,100 tonne (1,200 ton), 8.8 m (29 ft) diameter machines had a cutterhead thrust of 19,613 kN (4,413,000 lb) and generated a maximum torque of 12,748,645 N-m (9,410,000 lb-ft).

The undersea French side of the Channel Service Tunnel also required an EPBM. This machine featured a 5.6 m (18 ft) diameter cutterhead, a cutterhead thrust of 39,227 kN (8,837,000 lb), and a maximum torque of 3,510,781 N-m (2,591,000 lb-ft).

Two Double Shield TBMs were built for the U.K. terminal because fewer water inflows were predicted. Robbins designed these machines to withstand unstable and faulted rock conditions. The 8.36m (27 ft) diameter machines included 13 inch (330 mm) cutters and 65,871 kN (14,821,000 lb) of thrust. The machines generated a maximum 5,727,084 N-m (4,227,660 lb-ft) of torque.

Tunnel Excavation

Machines were deployed on both sides of the tunnels in December 1987. The three French seaward TBMs encountered water inflows almost immediately, forcing the use of the sealed mode of operation much earlier than anticipated. The sealed cutterheads of the machines could withstand 10 bar (145 psi) of water pressure; however, additional measures were required to seal the remainder of the machines against water inflow.

The tail shields of the TBMs were fitted with multiple rows of wire brush seals that pressed against the outside diameter of the concrete segment lining. Grease was injected into wire brushes and the 100 mm (4 in) space between the metallic brushes and the tunnel lining. Grout lines were fitted into the tail shield allowing fine cement grout to be injected into the 152 mm (6 in) annulus between the tunnel lining and the ground. This method sealed the tunnel lining as the TBMs advanced. In spite of the difficult conditions, advance rates improved throughout the boring with the Robbins service tunnel machine averaging 714 m (2,342 ft) per month for the project.

The U.K. machines also experienced some difficult tunneling conditions at the outset. Unforeseen water inflows in a 3.2 km (2.0 mi) stretch caused the machines to slow their progress as each section of tunnel had to be grouted in advance of boring. After passing through this section of tunnel, the machines experienced no further difficulties and began averaging 149 m (490 ft) a week. The Robbins machines on the U.K. side averaged 873 m (2,864 ft) per month and set world records for a best day of 75.5 m (247.7 ft), a best week of 428 m (1,404 ft), and a best month of 1,719 m (5,640 ft) — all of which have yet to be beaten.

Muck transport on both sides of the tunnel was complicated but worked well. In the U.K. a rail system of 500 muck cars transported muck back to the access adit at Lower Shakespeare Cliff and fed it onto a high-speed conveyor. The conveyor then dumped the muck into lagoons behind sea walls in the English Channel. In all, about 4 million m3 (5.23 million cubic yards) of chalk were dumped at the site. The area, called Samphire Hoe, is now a popular park.

On the French side muck was crushed and mixed with water in a chamber at the bottom of the Sangette access shaft. It was then pumped up the shaft and behind a 30.5m (100 ft) dammed reservoir.

In December 1990, the French and British TBMs met in the middle and completed the Channel Service Tunnel bore. In all of the tunnels the French TBM was dismantled while the U.K. TBM was turned aside and buried.

The Main Rail Tunnels met on May 22, 1991 and June 28, 1991. Both accomplishments were celebrated with breakthrough ceremonies to commemorate the building of one of the world’s longest and most ambitious undersea tunnels.

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Boston Harbor Project

Project Overview

The Boston Harbor Project includes one of the largest wastewater treatment plants in the United States. The project required two undersea tunnels to carry wastewater to and from the new treatment plant. One tunnel conveys treated waste water through a 15.2 km (9.4 mi) long effluent outfall tunnel beneath Boston Harbor. The outfall tunnel transports the water from the Deer Island Treatment Plant into Massachusetts Bay. Since the completion of the project in 1998, effluent discharges into Boston Harbor have ceased and concentrations of toxic bacteria, waste solids, and nitrogen have decreased dramatically.

In 1990, The Massachusetts Water Resource Authority awarded the construction contract to Kiewit-Atkinson-Kenny Joint Venture. The contractors selected an 8.1 m (26.5 ft) diameter Robbins Double Shield TBM to bore and install the lining in the effluent outfall tunnel.

Geology

The prominent rock type along the tunnel is Cambridge argillite in beds 1 mm to 8 cm (.04 to 3.15 in) thick with occasional 1.5 m (4.9 ft) formations. Volcanic flows and occasional tuff deposits are also embedded in the argillite. Other geologic features include igneous dikes and sills of diabase with some basalt, andesite, and felsite.

TBM and Back-up

Robbins built the Double Shield TBM to handle the variable geology of the undersea tunnel. While in “double shield mode” the machine simultaneously installed pre-cast concrete lining segments while excavating. This feature gave the machine a faster overall advance rate than with the sequential operation of “single shield mode”.

The machine’s cutterhead drive consisted of eight electric motors generating 2520 kW (3360 hp) and supplying 3665 kN-m (2,700,000 lb-ft) of torque to the cutterhead. The cutterhead thrust was 111,350 kN (2,500,000 lb) and the machine’s 50 – 17 in (432 mm) diameter cutters could be changed from behind or in front of the cutterhead.

The source of cutterhead thrust could also be changed depending on boring conditions. In good conditions (self-supporting ground, usually hard rock), the machine would bore in “double shield mode,” where thrust reacted through a conventional gripper system into the tunnel walls. In soil or fractured zones where the tunnel walls were too weak, the machine would operate in “single shield mode”, where the thrust reacted directly to the tunnel lining segments via a set of auxiliary cylinders in the tail shield.

The TBM towed a back-up train with eight 10.7 m (35 ft) long double-deck gantries, via hydraulic cylinders. The upper decks of the gantries housed the two main 2000 kVA transformers, electrical control cabinets, dust scrubber system and auxiliary equipment. Flexible 1.5 m (4.9 ft) diameter ducting extended from a storage cassette mounted on the last back-up gantry to provide ventilation. A double-track rail system installed on the first six gantries provided storage for rail cars carrying pre-cast segments and pea gravel for temporary segment support, rails and ties.

Tunnel Excavation

The TBM began excavating from the access shaft in July 1992. Early in the drive, the TBM battled more blocky rock than predicted in the geological reports. Hard rock and water inflows continued to slow progress throughout the drive.

In 1993 and again in 1995 and 1996, hard rock and heavy water inflows required face grouting and slowed TBM progress. Most of the water inflows reached rates of 19,000 to 26,600 liters (5,019 to 7,027 gallons) per minute. Probe drilling and grouting in these sections resulted in slower TBM advance rates.

From March 1996 onward, TBM excavation continued concurrently with hand excavation of the crossover adits. The machine broke through on September 19, 1996 after excavating over 15 km (9.3 mi). The TBM achieved a best day of 44.2 m (145 ft) and a best week of 195.1 m (640 ft).

This TBM’s achievements are remarkable considering the extremely high volume of water inflow and large variations in geology throughout the drive.

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The Epping to Chatswood Rail Link

Descripción del proyecto

La construcción del enlace ferroviario entre Epping Y Chatswood reprresenta la prolongación del sistema de trenes urbanos de Sydney (Australia). El proyecto comprende dos túneles paralelos de 12,5 km de longitud. El Gobierno regional de Nueva Gales del Sur adjudicó la construcción de los túneles a un consorcio germano-australiano compuesto por las empresas Hochtief y Theiss, denominado THJV.

THJV encargó a Robbins la fabricación de dos tuneladoras de 7,2 m de diámetro en 2002. Las tuneladoras perforaron los túneles desde la estación de Delhi Road, aproximadamente a la mitad del trazado de los mismos, dividiéndose el trabajo en dos conjuntos de dos perforaciones cada una y obteniendo unos índices de avance impresionantes a lo largo de todo el proyecto.

Geología

Ambos túneles atraviesan terrenos de arenisca de Hawkesbury y depósitos de pizarra de Ashfield. El terreno se encuentra fallado en la zona de la estación de Macquarie Park, a unos 2 km del comienzo de la perforación.

Tuneladoras y cintas transportadoras

Las dos tuneladoras abiertas disponían de una potencia en cabeza de 2300 kW, proporcionando un empuje de 1400 t. Robbins introdujo varias innovaciones en el diseño de las tuneladoras para este proyecto. El diseño especial del back-up rodante permitió la instalación de hormigón en solera para el desplazamiento de vehículos al mismo tiempo que la tuneladora perforaba el túnel, lo que hizo posible el uso de vehículos con neumáticos durante la perforación así como que facilitó la instalación de vía en el túnel.

Robbins también diseñó las cintas transportadoras a medida del proyecto, consistiendo el sistema en dos cintas horizontales, dos verticales y una cinta repartidora. Las cintas horizontales se instalaron en la clave del túnel y discurrieron durante 6 km con un porcentaje del 80% en curva.

Perforación del túnel

Las tuneladoras comenzaron la perforación de los túneles en agosto y septiembre de 2003, terminando ambas en Epping en Julio de 2004. En noviembre de 2004 comenzaron sus segundos túneles, calando en Chatswood en junio y Julio de 2005 respectivamente. Una de las máquinas estableció una nueva marca mundial para tuneladoras de su tamaño al alcanzar los 92 m de túnel perforado en un día. El mejor rendimiento semanal se estableció en 368 m, siendo la media de perforación de 200 m/semana. No se produjeron incidentes notables en el desempeño de las máquinas, cuya disponibilidad se evaluó en el 80% del tiempo total del proyecto.

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New Wuchieh Diversion Tunnel

Descripción del proyecto

El túnel de desvío de aguas de Wuchieh forma parte de un proyecto de trasvase de aguas que alimenta a la central hidroeléctrica del lago Sol-Luna, una de las más grandes de Taiwán. El propietario del proyecto, Taipower, encargó la construcción del Nuevo túnel de desvío, de 6,3 km de longitud, ante el deterioro del túnel original de desvío de Wuchieh, agrietado y con pérdidas después de 70 años de servicio.

El túnel trasvasa el agua desde el  lago Sol-Luna hasta la estructura de toma de la central hidroeléctrica. Este nuevo túnel, junto a otro que también trasvasa desde dicho lago, aumentará la generación de potencia de la central hasta alcanzar los 7.600.000 kWh anuales.

Taipower adjudicó el contrato de construcción del túnel al contratista japonés Kumagi Gumi Co., que decidió ejecutarlo mediante el uso de una tuneladora abierta Robbins de 6,2 m de diámetro.

Geología

La traza del túnel atraviesa zonas de cuarcita, arenisca y pizarra, que aparecen fracturadas en varios tramos de la misma.

TBM

Robbins reconstruyó una tuneladora abierta de 6,2 m de diámetro para el Nuevo túnel de Wuchieh, equipada con cortadores de 17” y cierre en cuña y 1.890 kW de potencia en cabeza. La máquina, de 380 t de peso, era capaz de suministrar un par de 1.774.415 Nm.

Excavación del túnel

La tuneladora comenzó sus trabajos en Julio de 2000 y lo terminó en 24 meses, el 7 de junio de 2002. La media de avances mensuales sobrepasó los 400 m con un mejor mes de 650 m. A la mitad de la perforación se encontraron terrenos fracturados, donde se aplicaron métodos de sostenimiento como cerchas, malla y gunita (hormigón proyectado). Se revistieron Además, algunas secciones del túnel se revistieron con piezas de acero de fundición para aportar sostenimiento adicional.

En septiembre de 2001 la obra sufrió las inclemencias del tifón Toraji, que la inundó de barro, sumergiendo incluso algunos de los contenedores de repuestos, cortadores y los utilizados como taller. Afortunadamente el nivel del barro nunca sobrepasó el de trabajo en el túnel por lo que las operaciones simplemente se retrasaron. El resto de la excavación transcurrió sin problemas y la terminación del túnel se celebró como la primera perforación exclusivamente con tuneladora realizada en Taiwán.

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