Foundations

With the human population burgeoning and people flowing into cities, the development of metro stations, ports, dams, and residential and commercial areas has created a growing need for deep foundations.

The redevelopment of existing sites in urban areas calls for compact equipment that can be used in tight spaces; and as infrastructure spills out into new areas, ever-bigger projects demand more precise foundations on a larger scale.

One such large-scale urban development project currently underway is the £8 billion ($10.8 billion) renovation of the Battersea Power Station in London, UK, where Bauer has been executing specialist foundation engineering works.

Renovation of the site began in 2013, to create a complex of residential areas, retail outlets, workplaces, galleries, markets, restaurants and pedestrian streets. Bauer was awarded the phase 2 foundations contract at the start of 2016.

The English subsidiary of Bauer Spezialtiefbau is carrying out the foundation work from within the existing structure of the former power station, which was said to present some major challenges in terms of access to the construction site, working space and headroom.

“These factors dictate the timing and the construction techniques that are used”, said project director Paul Doyle. “For example, before specialist foundation engineering works can be carried out, removal of hazardous waste, such as asbestos or animal waste, is undertaken to allow safe access.”

Before the main works began, Bauer carried out various preliminary works, including the construction of test piles and the removal of old foundations and redundant piles. The redundant piles ranged from 300 to 900mm in diameter, with a variety of depths from 12 to over 30m, and were removed by inserting a casing tube into the ground around each pile and then breaking up the pile within the casing by means of a drill.

The resulting borehole was then filled with low-strength concrete, so that Bauer could install a new foundation pile in that location during the next phase.

The main works followed, including the installation of two very large secant pile walls inside what were originally the Turbine Halls.

Doyle said, “Installation of these walls was far from easy, as access – including headroom – was severely restricted.” Over 500 secant piles – 1,000mm in diameter and up to 26m deep – were installed in the two basement excavations.

Powerful performance

Two new Bauer BG 39 drilling rigs, a BG 40 and three duty cycle cranes were delivered to the site. Due to space restrictions, the masts for the BG rigs were delivered on separate low loaders, together with the drilling tools and the Kelly bar, and were re-assembled within the building.

The scope of the piling includes 480 supporting piles ranging from 750 to 2,100mm in diameter, drilled down to a depth of up to 63m, and 500 secant piles. Drilling work is expected to be completed by the end of 2017.

JCB has also been involved in the Battersea Power Station development, providing a new fleet of crawler excavators that shifted more than 50,000m³ of earth on the site, as part of the foundation works.

The concrete frame specialists MPB Structures purchased three JS220LC and two JS130LC models specifically for the contract.

Pat Boyle, director of MPB Structures, said, “We chose them to match the specific emissions and health and safety demands of the Battersea Power Station development and have selected a range of options to ensure the protection of our operators and those on site.”

The machines carried out bulk excavation duties, as well as creating a service trench and loading the removed spoil into dumpers to be taken off site by road.

Following the complex excavation process, which involved digging to a depth of 8.5m and installing temporary props to retain earth, MPB Structures will insert pile walls to create the basement area for the new development.

Core project

Another large project has been taking place on the other side of the globe, in Kuala Lumpur, Malaysia. A new Liebherr LB 44-510 – the manufacturer’s biggest rotary drilling rig – is part of a fleet of foundations equipment that is being deployed by Malaysian foundations and geotechnical specialist Aneka Jaringan on the city’s Sentral Suites project. It is working alongside a new Liebherr LB 36 rig, which is the second largest machine in the company’s range.

This landmark development in Kuala Lumpur’s new-generation central business district will include three towers, the tallest of which will be 45 storeys. Aneka Jaringan started on the site in January 2017 and is working to an 18-month schedule.

Loke Kien Tuck, director of Aneka Jaringan, said, “Because of the local regulations, the site can work only between the hours of 8am and 7pm. We therefore have to work quickly, and the two machines are proving to be very fast. The ground is quite hard, being mostly silty sand, and we are taking between five and six hours to bore down to between 30 and 35m. That means we can complete the boring and casing installation in one day, and then pour the concrete the following morning.”

The two rigs are boring to depths of up to 35m, with a maximum pile diameter of 1.8m, and were delivered with an extensive training package for the contractor’s operators and service personnel.

In Egypt’s capital, Cairo, equipment manufacturer Soilmec has provided a number of rigs for a project that is aimed at addressing the city’s traffic congestion problem.

To better cope with the 3.3 million cars that use Cairo’s roads every day, the Rod El Farag project will connect the existing ring road around the city with the Cairo-Alexandria Desert Highway, providing an alternative route to the heavily congested roads.

The Rod El Farag Highway will be approximately 35km long, with eight lanes – four in each direction – and a service lane on each side. The project also includes the construction of two bridges across the River Nile, one 260m wide and the other 180m wide.

Building information modelling

The job site is mostly flat and stands between 1.5 and 2m above sea level, on average. The stratigraphy consists primarily of two formations: silty clay that is relatively soft in consistency, and dense silty sand. There are also some layers of very compact, hard silty clay.

Among the rigs supplied by Soilmec are the SR-45 and SR-60, which were said to be flexible and with fast operating capacities. They are driving piles with a diameter of 1,000mm to a maximum depth of 31m. The excavation work is being performed using bentonite mud and bucket tools, and it is expected that 3,000 piles will be required in total.

Inaccuracies and inefficiencies in foundation works become all the more costly the larger a project is, and new technology can offer a solution.

The Federation of Piling Specialists (FPS) has called for greater main contractor awareness of how BIM (building information modelling) can be used to benefit below-ground construction – specifically piling and substructure work.

The move follows feedback from a recent survey it undertook to look at the impact of BIM on the piling and substructure industry, in which more than 80% of respondents confirmed its beneficial impact, yet also found little call from clients for its application.

Speaking about the findings, Mark Pennington, leading the FPS BIM Working Group, said, “Great progress has been made in recent years with regard to BIM and its adoption into all areas of construction. However, there is still much to be done in widening its application to below-ground construction techniques, such as piling and foundation works.”

He added, “The understanding of digital construction must evolve so that BIM users recognise that it does apply to all construction areas, including piling.”

The FPS, as part of its BIM activity, is raising awareness at all client levels of the technology’s potential benefits to its members’ services and activities.

Over the coming months, the FPS will be looking at ways to engage further with clients to ensure the benefits of BIM to piling and foundation works are more widely recognised and taken advantage of.

In particular, the FPS is working with the AGS Data Management Committee to investigate the possibility of using the AGS format for piling information. This would provide a platform for the transfer of piling design and construction information in a digital format.