Franki Defies Challenges To Meet Landmark Project’s Tight Programme

Franki Defies Challenges To Meet Landmark Project’s Tight Programme

An optimised design to match a taxing contract programme was instrumental in Franki Africa’s ability to hand over the challenging foundations and lateral support work for the landmark 144 Oxford project on time.

Franki Africa was recently contracted to provide geotechnical services for the ground-breaking 144 Oxford project, a flagship 35 000 m² development by Growthpoint Properties. Located on Oxford Road in Rosebank, Johannesburg, the development is set for completion this month. When complete, the 35 000 m² development, will establish a new landmark office address in Rosebank with an innovative design that supports modern businesses to thrive and evolve.

Franki was responsible for the design, supply and installation of the earth retaining lateral support system and the piled foundations of this development. The project scope included a five-level basement to a maximum depth of 15 m below natural ground level with a total of 5 755 m² of lateral support, as well as 235 no. foundation piles with column loads varying between 3 800 and 15 000 kN.

Contract programme

According to Brett Markides, Senior Design Engineer at Franki Africa, from the onset, the contract programme proposed by the client proved challenging. However, the development was considered a key project for Franki, and an optimised design to match the contract programme was fundamental to winning the tender in such a competitive market.

The west elevation of the development incorporated a Gautrain servitude roughly 12 m beyond the site boundary where no structural elements of any lateral system could be installed through. The solutions to this problem were not immediately obvious as the servitude posed a restriction on the anchor lengths required for conventional lateral support. “The design team at Franki had to revert to first principles and hand calculations to conceptualise a workable solution that would account for this restriction,” explains Markides.

Changes in design were a constant challenge and design development had to conform to the engineers’ and clients’ specifications. In this regard, Franki relied heavily on its uniquely integral in-house design team to deal with the changes as and when they occurred, as well as providing cost-effective workable solutions to the professional teams.

Ultimately, an innovative design solution was proposed by Franki that would meet the engineers’ specifications, and from a commercial standpoint, the programme would be achievable,” says Markides.

Challenges in lateral support

The design of the lateral support system on the North, East and South elevations comprised soldier piles with a system of active and passive support in the form of anchors.

On the west elevation, an initial cut back and batter was proposed to reduce the retained height of the wall, effectively reducing the lateral forces and mitigating the requirement for structural elements extending into the Gautrain Servitude. The west elevation comprised soldier piles with a similar system of alternative active and passive support,” explains Markides.

Franki developed a fully working FEM model in Plaxis 2D, capable of staged construction analysis and analysed all expected forces in structural elements and factors of safety at all construction stages. Verification of stability and deflections in the temporary and permanent state were analysed and checked against the required specifications. The resulting output confirmed the expected modes of failure at the factor of safety stages, and the model was deemed appropriate for the design solution.

Verification of the design followed an observational approach on site through stringent monitoring to ensure predicted vs actual deflections aligned throughout construction. Accurate and up-to-date record keeping was critical to the project’s success.

Due to the innovative design process, health and safety considerations were incorporated by employing well understood and recognised methodologies in Franki, so that neither additional risk would be placed onto the site teams nor would any unfamiliar construction methodologies be introduced. “As part of the design process, an integrated risk-management analysis was undertaken to highlight any potential concerns that might arise from a technical standpoint,” says Markides.

Piling

The geotechnical information indicated competent rock granite between 5 m and 15 m below bulk excavation level. Auger cast in-situ piles socketed into competent rock were chosen as the most economical piling solution, and Franki optimised the pile layout to accommodate higher loads on fewer piles.

This was made possible with specialised cleaning tools to effectively clean the pile bases through mechanical action as opposed to cleaning the bases by hand,” concludes Markides.

Franki pulls out all stops to unravel brewing challenges at Mozambican project

Franki Africa overcomes an array of challenges at the construction of a new brewery in Mozambique

Franki pulls out all stops to unravel brewing challenges at Mozambican project

An ambitious project timeline for the construction of Cervejas de Mozambique’s new brewery, compounded by a late start to the project due to external constraints, saw geotechnical specialist Franki pull out all the stops to ensure partial handovers of the foundations and lateral support to allow the main contractor to carry on with the works.

Franki piling while the sun goes down in Marracuene. From left to right: Ajax Crane with leader, Franki Crawler Rig and Casagrande CFA 26.

Franki Africa is once again proving why it is the largest, oldest and most established specialist geotechnical contractor in sub-Saharan Africa. This time, the contractor is calling on its experience in this specialist field to get the better of an array of challenges at the construction of a new brewery in Mozambique. The project owner, Cervejas de Mozambique (CDM), which already owns three breweries in the country, is a subsidiary of the largest global beer brewer, AB InBev.

Having broken ground on the construction of a more than 2-million hectolitre a year brewery to be built at a total cost of US$180-million in Mozambique’s Marracuene district, about 30 km north of Maputo, CDM went on to lay the first stone for the construction of the new brewery in early December last year. The project is the largest investment by CDM and by the beer sector at large in Mozambique since CDM’s inception back in 1995.

Aerial view of the site, showing Franki’s three piling rigs

The new brewery, scheduled to produce its first batch of beers by the end of this year, means that its construction has a very tight timeline. Franki has been entrusted to carry out geotechnical work on the project. Marta Botelho, Contracts Engineer at Franki Mozambique, explains that Franki is responsible for the installation of foundation and lateral support piling for different structures of the brewery, like the BBT Tanks and Unitanks, Raw Material Silos, Malt Intake and Mill House.

With an initial estimated duration of five weeks, Franki’s project duration has since been extended to 10 weeks. As a result, the contract value has increased from MZN79-million (about R21,5-million) to MZN129-million (about R35,1-million) due to additional works required. A late start to the project meant a major setback to the project’s stringent timeline.

Installation of CFA piles for the Malt Intake lateral support structure

Apart from the late start, Botelho says the tight nature of the timeline was just a big challenge from the start, adding that the programme is very tight, due to the client’s plans to start operations this year.

After a late start, we managed to guarantee partial handovers of the different areas in order to allow the main contractor to carry on with the works,” says Botelho. “Our design team worked together with the client’s engineers (WSP) to get to the best solutions and overcome any arising challenges.”

Another key challenge the Franki team had to contend with was the short supply of readymix concrete. There is a long distance from an existing batch plant to the site. “We used different suppliers and our own concrete transit mixers to minimise this challenge. Due to the tight nature of the programme, we also had to resort to working extended hours,” says Botelho.

With a total of 60 people on site, including 18 subcontractors for steel fixing, Franki’s project scope encompasses different piling technologies, including the Continuous Flight Auger (CFA) piles and the Driven Cast-in-situ piles, also known as Franki Piles, with diameters ranging from 410 to 800 mm. Franki will install a total of 707 piles, comprising 142 no. CFA and 367 no. DCIS foundation piles, as well as 81 no. Grout Columns, 117 no. CFA piles and 243 m² of Gunite arches in lateral support.

Franki with all their “ducks in a row”

Commenting on the choice of piles, Botelho says CFA piling is a fast system with no vibration and limited noise levels associated with it. Franki Piles, on the other hand, are the most economical and reliable piling system in southern Africa. Developed about 70 years ago, the Franki Pile’s main feature is the large base formed at the toe of the pile and, in forming it, the end-bearing area is considerably increased. Generally a very economical system, it has an extensive range of pile sizes.

To execute the project, Franki has a range of equipment for each of the setups. For the CFA setup, the geotechnical contractor has deployed the Casagrande CFA-26 auger rig and the Sany HBT-40 concrete pump. A Franki Rig SA83 and a 60t Ajax C60 are being utilised for DCIS setup. In terms of auxiliary equipment, Franki has deployed a Tadano TI mobile crane, the two Fiori transit mixers and two TLBs. “For lateral support equipment, we have on site a Comaachio Geo 305 drill rig and a single Mat Pump. Proper selection of equipment is very crucial to ensure timely delivery of the project,” concludes Botelho.