Demolition goes underground in Rotterdam - the new HSL-South high speed rail line

06 October 2010

The construction of the new HSL-South high speed rail line in the Netherlands has created a major underground demolition challenge for Dutch contractor Struijk-Groepin in the city of Rotterdam. D&Ri reports.

Against the backdrop of a dominating skyline of tower blocks, Rotterdam's new inner-city transport interchange, Centraal, is an unusual mix of ultra-modern and practical glass architecture and masses of green spaces.

By 2012, today's artist's impressions will become reality, with an underground station, a new train station, parking for both cars and bicycles, bus lanes, car lanes, taxi lanes and interchangeable boulevards.

The daily number of travellers and visitors, already touching 110,000, will no longer have to squeeze past construction site barriers.

By 2025, when the HSL-South high-speed track starts running from the new train station into the European rail network, the city, which experienced a massive boom mainly from its oil and container port, is expected to see around 320,000 people pass through this intersection every day in some form or another.

The cost of the entire project has been calculated in 2008 at around € 370 million (US$490 million).

However, this is a mega construction site - above street-level but particularly underground. Unlike most construction projects in the Netherlands' interior - away from the coast - every technician working on this high-rise, subterranean, canal and tunnel build has been in close collaboration with hydraulic engineers - a specialist area in which the Dutch have the best reputation in the world; not least because they are aware of their vulnerability.

Most streets in the Dutch delta city are below sea level and the excavators need dig only half way in to almost reach ground water. And yet, the delta branches of the Rhine - old and new Meuse, Lek and many more, including the Ijssel - are traversed by a total of eleven railway and road tunnels.

The lowest levels of the underground stations and inner-city underground tunnels lie in depths of up to 23 metres. Foundations are secured with tie rods of over 40 metres in length to protect them against flooding; large underground lobbies stand in caisson-type structures protected from water penetration and if that does not work, the subsoil water is tricked with freezing method; even caves of alluvial sand do not form any great obstacles.

In close proximity

By 25th September 2009, designs for almost half of the new, spaciously designed and light-filled metro stations had been approved. Before reconstruction could start, the old 1960s section, an area of 15,000 m3 with around 8,000 tonnes of reinforced concrete steel B50s (a steel component of around 700 tonnes), had to be demolished.

Having the best knowledge of the local conditions, the demolition specialist, Struijk-Groep, from nearby Krimpen aan de Lek, was commissioned with this task - the company had already performed other demolition jobs for the mega project when it was started.

In November 2009, work started on the final section of the Centraal, with a completion date of the end of January 2010.

"First we had to break into the upper layer - up to 1.3 m (4.3 ft) thick in parts - so we could use two telescopic mobile cranes to drop our demolition machines and tools down onto the flat work surface, 35 m (115 ft) underground.

"When using the excavator-mounted breaker for demolition work, and when crane-lifting the excavator, we had to work very closely against the large, horizontal, steel pipe wall supports which were up to 52 m in length.

"This site is particularly demanding when it comes to moving freely in a very tight working area and, because we are dealing with high levels of public traffic, dust emissions have to be effectively controlled.

"We also had demand a high level of concentration from our excavator drivers who were working with an operational underground line - the excavator and boom tools were often less than 1 m (3.3 ft) away from the running trains", said Allard Struijk, one of the two managing directors, explaining the construction situation.

The Struijk site is divided into two working areas: The primary machine working on the lower base level is a Komatsu PC450 (45 tonne/257kW) with a quick-coupler as standard.

The main tool being used on this machine is a 6,400 kg (14,080 lb) ACDE-Okada TSW-1800 VFR concrete cutter. This is the largest concrete crusher that can be carried by 45 tonne class machines in the world. It can also be used on machines up to 1000 tonnes.

The TS-W1800V primary crusher is capable of demolishing huge amounts of concrete. A longer jaw length and depth creates more disposal volume.

The jaw and frame are made using cast high tensile strength steel that is wear resistant to make a tool with light weight and high rigidity. The jaw is designed and shaped like a "sharp wedge" in order to penetrate the material being processed.

The PC450 also uses a silenced, 4,000 kg, Sandvik G 100 City breaker, a 2.5 m3 demolition backhoe and sorting grab.

Meanwhile, in the lower sections of the site, a Hitachi 135 zero tail swing excavator is working with a number of other tools. These include a silenced Okada TOP 100a breaker, a 1,400 kg (3,080 lb) Okada TSW 950 VFR concrete crusher.

Other machines on the site include a Hitachi 28 min-excavator equipped with an 270 kg (594 lb) silenced ACDE DMS 330 hydraulic hammer and a T 175 Bobcat tracked loader.

The resulting demolition waste, broken roughly into smaller pieces, is lifted from the pit in certified 5 m3 containers by a Hitachi KH 180 excavator. A water cannon is used to efficiently control dust during these operations.

The resulting material is stockpiled in the upper area of the site, with a Fiat-Hitachi KH 150 crawler crane taking care of the container work.

An Hitachi 350 crawler excavator (a Liebherr 914 crawler excavator was rented in the short term) uses a 2,800 kg (6,160 lb) Okada OSC 100 V Euro concrete crusher in the secondary demolition role to break up the chunks and separate the concrete from the steel.

The rebar is then segregated by a 14 tonne Hitachi 135 excavator mounted with a electromagnet and dumped into the containers.

There are also two T175 and 561 Bobcats and two Fiat-Hitachi 50VX and 45 mini excavators. The concrete and steel are transported to local specialist recycling firms for further processing and resale.

A total of 15 to 20 Struijk employees are working in two shifts, seven days a week, on the site. The demolition work is currently on schedule to be finished by the end of January or early February 2010.

About Strujik

Strujik-Groep was founded in 1938 by Marinus Johannes Strujik as an agricultural service company. At the end of World War II it moved in demolition, removing the detritus of bomb and shell damage in Rotterdam. Strujik is now managed by the third generation of Strujiks, Edward and Allard.

It can look back on a long history of successfully completed demolition projects including the train stations at Dordrecht, The Hague, Leiden and Amsterdam, 22 bridges to make way for the new, 169 km-long Betuweroute railway line and the high-speed HSL-South track.

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