Grouted steel anchor piles, a first in SA, installed in Maydon Wharf
Our Q&A with Shane Perumal
John Thomé of South African Builder talks to Shane Perumal, Project Manager, Transnet Capital Projects, about the unusual technology of installing grouted steel anchor piles, being applied for the first time in South Africa, in the Transnet National Ports Authority’s project to reconstruct the quay walls and deepen berths at Maydon Wharf in Durban.
The R1.6 billion project forms an integral part of Transnet’s Market Demand Strategy which aims to enable the effective, efficient and economic functioning of an integrated port system to promote economic growth.
Work includes driving of inclined grouted steel anchor piles, backfilling behind the quay walls, construction of new reinforced concrete capping beams, supply and installation of bollards, fenders, ladders and quay services, construction of railway tracks, layer works and paving, dredging of material adjacent to the berths and construction of rock scour protection.
John: Tell us about the basic design, function and advantages of the “inclined grouted steel anchor piles.”
Shane: The Mȗller Verpress (MV piles) are steel tension elements with a grout layer. They are installed by driving a steel beam into the ground, with continuous injection of a grout mix. The piles normally have an H-shaped core. The toe at the end of the pile is fitted with a box-like “shoe” wider than the core. Grout is fed to this shoe through steel or plastic pipes attached to the beam.
The pile is driven using a hydraulic impact hammer rigged in leader configuration. As the pile is being driven, the wider shoe creates a void around the core. This is filled immediately with a cement based grout fed upward from the shoe. The liquid grout initially acts as a lubricant during installation. It then hardens to anchor the pile in the ground. To ensure the quality of the process, the rate of grout injection is monitored carefully throughout the installation. The piles are suitable for very heavy loading and, because of the grout injection, can be installed to great depth in varying soil conditions.
John: What is different about this method of piling that lends itself to this application? Shane: This system of pile anchorage is particularly suited to the conditions at Maydon Wharf where conventional anchorage systems cannot be used owing to a lack of space. As the working apron is narrow, with buildings and warehouses close to the quay walls, there is insufficient space for the construction of conventional anchors which are installed horizontally and would extend into the buildings. As the MV piles are installed at a 45° angle, they can be installed without unnecessarily disrupting working access behind the quays or interfering with building infrastructure.
John: Where was the technique developed? And how did it come about?
Shane: The system was developed in Germany. Many ports are located in areas of poor geology where it is necessary to install anchors to great depth to achieve the required tensile capacity.
John: Why steel?
Shane: Steel has the highest strength to weight ratio of typical construction materials. The steel pile has a compact cross section which allows for it to be driven to great depth, whilst having the required tensile capacity to withstand the pull-out forces.
John: How is corrosion prevented in such a hostile environment?
Shane: As the pile is fully coated by the grout envelope, it is protected from corrosion. It is noted also that owing to a lack of oxygen below ground level and the water table at depth, there is limited capacity for corrosion.
John: Who manufactures and supplies the piles?
Shane: Pile manufacturers such as Arcelor-Mittal supply a wide range of piles, including the H-piles from which the MV piles are fabricated. Fabrication, including the shoes and grout delivery systems etc. are generally fabricated by the contractor on site. In this instance the H profile pile was manufactured in Luxembourg and shipped over for on-site completion here.
John: Describe some of the trials and tribulations of the project.
Shane: The main challenges have been balancing operations and the project, including site access, executing work around the existing ship loader foundations and conveyor, as well as obstructions and incorrect as built information supplied. The project team has also had to contend with strong winds and wakes formed by tugs operating in the precinct affecting floating equipment used for construction.
As a result the team has implemented night and weekend shifts and mobilised additional plant to ensure that the project remains on track.
On tribulations, achievements to date include a satisfactory audit report, the successful pull out test on the anchor pile system and the completion of all piling and the new cope on Berth 1,2 & 13. Also, a record 4 500 tonnes of steel was offloaded, transported and stacked during a continuous 84 hour operation.
The most important though was our safety milestone of 1 million hours without a lost-time injury (LTI). This could not have been achieved without an enormous amount of hard work and effort by everyone working on the project.
Maydon Wharf is the largest break bulk and dry bulk handling precinct in the Port of Durban covering 120 ha of port land. The reconstruction project aims to ensure safe operations, meet the needs of larger vessels calling at the port and enable increased throughputs. The upgrade involves the reconstruction and deepening of six of the 15 berths in this precinct.
The work has involved demolition of paving, rail track work and services, construction of new steel sheet piled quay walls, demolition of existing piled crane beams, extraction of timber, concrete piles and a limited number of steel sheet piles and removal of the existing quay wall and capping beams.
Once completed the berths will have a draught of 14.5 m enabling them to handle vessels with draughts up to 13 m, however the Maydon Wharf entrance channel will still need to be deepened thereafter to enable these vessels to sail in fully laden.
On Health and Safety
The project recently achieved a safety milestone of 1 000 000 Man Hours without a Lost-Time Injury (LTI) on the Reconstruction and Deepening of Maydon Wharf Berth 1- 4, 13 &14 Project.
“There has been a huge safety commitment from the Project Managers, the main contractor Stefanutti Stocks AXSYS Joint Venture, and subcontractors, to provide continual training, preventative programmes, communication of safe work practices, sharing of lessons learned from observations and incidents and good site safety vigilance. This ensures that everyone – from labourers to senior management- works safely every day,” says Project Manager, Shane Perumal.