Two pipe jacking projects, which together comprise 44 jacks totalling 1 456 m, have further boosted civil engineering and construction company Esor Africa’s reputation as one of South Africa’s leading pipe jacking companies, it reports.
The projects involve a complex sewer reticulation upgrade in Gaborone, Botswana, and a petrochemicals pipeline running from Secunda to Sasolburg.The Gaborone Project
Esor Africa’s senior contracts manager, Anton Naude, says that the Gaborone project, which is a sewer reticulation upgrade, has been challenging for different reasons.“It requires a good deal of organisation to gain access to the various jacking sites because they run across the city centre.
Most of the time, there is very little space to work in, as the sites are often located between a road and a built structure, leaving very little room to sink the jacking pit,” he says.Naude adds that the ground conditions have also not been that easy, with the water table being high and hard rock being encountered at many of the sites. “This job requires extensive pumping to remove the water, and rock breakers or even blasting to get through the rock on several of the sites.”
However, the company reports that the greatest challenge is having to take precautions to maintain the integrity of the final sewer pipes and to prevent leaks that could lead to the undermining of the inner-city roads. “To this end, the jacked pipe is merely a protective concrete sleeve into which the final sewer pipe is installed and then encased in concrete to ensure maximum stability and integrity for the lifetime of the sewer,” says Naude.
Sleeve Jacking and Final Sewer Installation Procedure
A concrete sleeve pipe was jacked into posi- tion. A system of premanufactured rails was then accurately installed within the pipe sleeve to the final sewer grade and the sewer pipes were then jacked into position, one at a time. This process was repeated until the whole sewer pipe had been jacked into position and then encased in a cementitious grout, using brickwork as stop ends.
The annulus between the sewer pipe and the sleeve was grouted up to the top of the brickwork level in stages, until the complete pipe was encased.
Naude says that Esor Africa has worked closely on this job with specialist design engineer Jones & Wagner. “Over the years, we have developed a mutual understanding, which has helped us overcome most challenges encountered in countless conditions and situations.”
One of the more peculiar aspects of the Gaborone project is that the pipes have been supplied by Southern Pipelines, in South Africa, the company reports. “Ironically, it is cheaper to transport the pipes from South Africa than it is to buy them in Gaborone. This has been the case, in spite of the fact that 665 m of pipes with a diameter of 2,4 m were transported more than 700 km (round trip) by truck. “This involved 300 trips and a staggering 21 000 km in total,” the company reports.
The project, worth more than R30-million, started in February last year and will be completed in June.
The Secunda to Sasolburg Pipeline
The Secunda to Sasolburg pipeline is about 146 km long. Esor Africa was awarded the pipe-jacking portion of the contract, which comprises 23 road and rail crossings at various points, totalling 791 m, by main contractor WBHO.
Esor Africa contracts manager Gideon Lesia says: “We have eight teams on the job and, thus far, most of the sites have presented ideal jacking conditions with firm, dense soil.”
He adds that the vast majority of jackings will be under roads, but that there will be some railway lines.
Lesia says that Sasol is uncompromising about health and safety regulations, which have to be strictly adhered to. “Although this is sometimes challenging from an operational point of view, we obviously welcome working in a disciplined environment,” he says.
The first phase of the Sasol pipe jacking project started in May last year, and is expected to be completed in March.
Esor Africa is a division of JSE-listed construction company Esorfranki. Through strat- egic acquisition, Esorfranki has diversified to the extent that it now offers a wide spectrum of construction services. “While our services, which were historically confined to geotechnical and related services, now include general civils and pipe laying, we have been careful to stick to the specialist principle,” says Esorfranki CEO Bernie Krone.
Source: Engineering News