Dam walls are some of Jet Demolition’s most innovative projects to date

25 March 2019
Jet Demolition’s work on large water-retaining dams constitute some of the most important projects that the specialist contractor has undertaken to date. These projects call for highly-controlled, cautious, partial demolition techniques.
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PreviewAt Hazelmere, the existing spillway crest, piers, lintel beam, and bridge decks were demolished.2.84 MBDownload
PreviewHazelmere Dam saw the compilation of specific demolition-control guidelines.1.49 MBDownload
PreviewJet Demolition Director Joe Brinkmann.3.42 MBDownload
PreviewJet Demolition has developed new blasting techniques to retain the structural stability of dams.5.95 MBDownload
PreviewJet Demolition used cranes to lower the demolition excavators onto the Hazelmere Dam wall.4.4 MBDownload
PreviewThe Full Supply Level (FSL) of Hazelmere Dam was raised by replacing the original Radial Arm Gate design with a Piano Key Weir.1.82 MBDownload
video/mp4 iconDam walls are some of Jet Demolitions most innovative projects to date2.47 MBDownload

New blasting techniques have been developed specifically to retain the structural stability of the dams themselves, with no wasted effort. “We look forward to other challenging work of this nature,” Jet Demolition Director Joe Brinkmann (Pr. Eng.) asserts.

Rehabilitation of dam walls usually requires demolition of redundant portions of monolithic blocks and associated concrete structures. Dynamic energy imparted by the demolition process has the potential to cause damage to concrete located just across the demolition boundaries and beyond. While it is essential to avoid damage to remaining concrete, it is also important to carry out the demolition works in a productive and cost-effective manner.

Hence, informed and judicious selection of demolition methods and their application techniques are vital to a controlled and productive project – which is where Jet Demolition’s extensive experience stands it in good stead, Contracts Manager Kate Bester (N. Dip. Civil Engineering) explains.

“Our work at Hazelmere Dam allowed for the compilation of specific demolition-control guidelines to be developed for dam rehabilitation projects,” Bester highlights. Here a combination of explosive, mechanical, and diamond-cutting methods were employed.

“In particular, it was demonstrated that explosives can be used as the primary method of demolition on dam rehabilitation projects in a safe, productive, and controlled manner, without causing damage to the remaining mass concrete and concrete structures.”

Located on the Mdloti River in KwaZulu-Natal, the Hazelmere Dam was built in the 1970s. It was designed originally to accept radial arm gates to raise the Full Supply Level (FSL). However, a subsequent redesign showed that the FSL would be achieved optimally via a Piano Key Weir (PKW).

To clear the way for new construction works, demolition of the existing spillway crest, piers, lintel beam, and bridge decks required the controlled removal of 5 300 m3 of concrete up to 3 m in thickness. “The key requirements were to demolish the redundant structures in a safe, rapid, cost-effective, and controlled manner, without residual damage,” Bester elaborates.

The traditional demolition method for projects with large volumes of mass concrete is explosives, with large hydraulic hammers used for the smaller concrete sections and for secondary breakage. Finishing work is typically undertaken by small hydraulic hammers and handheld breakers.

Despite the advances in diamond-cutting technologies, this method is usually not practical nor cost-effective to apply in isolation. The use of drilling and blasting is unrivalled in terms of speed and cost-effectiveness. However, for obvious dam-safety reasons, maintaining the structural integrity of the remaining concrete is a perennial concern when demolition works are carried out on a dam structure, or in nearby rock.

Due to the energetic and destructive nature of explosives, valid concerns of damage to the remaining mass concrete and concrete structures are at the fore when blasting is considered for dam rehabilitation works.

Drilling and blasting: It is possible to combine advances in drilling and wire-rope cutting technologies to effectively prepare the superstructure for isolated and highly-controlled micro-blasting activities.  A cautious and thoroughly detailed design approach is critical to ensure that no additional damage will be introduced into the structure, whilst optimising production and safety.  Whilst this option inherently introduces a new element of risk to the works, proven experience, technical data and a critical review of site-specific factors all channel into a systematic, practical and effective approach. 

Mechanical demolition and clearing: Mechanical demolition is a key facet of partial dam wall demolition, but only if executed with precision and due care.  “Jet Demolition has developed a range of highly specialised tools and attachments, specifically targeted at offering the utmost control in sensitive projects,” Bester states. “Our range of tools and equipment is not generally available in South Africa, and contributes to our commitment to safety and mechanisation.”

When considering safe blasting vibration levels for a particular project, it is of critical importance that cognizance is taken of the prevailing site conditions and geometrical configurations. “At Hazelmere Dam, our production blasting programme and demolition methods achieved all of these objectives successfully,” Brinkmann concludes.


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Notes to the Editor
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About Jet Demolition

Jet Demolition has been undertaking industrial demolition works since 1994, and is the leading, largest, and most technically-advanced demolition company in Africa. It offers in-house, full-range demolition services, including advanced mechanical solutions and controlled implosions. It actively pursues ongoing development of skills and equipment suited to the changing needs of the industry.

Jet Demolition is a technically-based company, with various staff members holding MSc, BSc, and BTech Degrees, as well as National Diplomas, in various engineering fields. This expertise gives it the technical foundation to successfully engineer solutions for large and complex demolition projects, and furthermore fuels its drive to deliver quality projects safely. Jet Demolition strives to offer its clients innovative and technical solutions to demanding demolition challenges.

Jet Demolition Contact

Kate Bester (N. Dip. Civil Engineering)

Contracts Manager

Phone: (011) 495 3800

Cell: 072 811 5310

Email: kate [at] jetdemolition [dot] co [dot] za

Web: www.jetdemolition.co.za

Media Contact

Renay Tandy

NGAGE Public Relations

Phone: (011) 867 7763

Fax: 086 512 3352

Cell: 082 562 5088

Email: renay [at] ngage [dot] co [dot] za

Web: www.ngage.co.za

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