The Kariba Dam Rehabilitation Project – Hydrodemolition

The Kariba Dam Rehabilitation Project

Standing 128 metres tall and stretching 579 metres as it spans the powerful Zambezi River, the Kariba Dam is undergoing refurbishment to ensure its continued safe operation. The Government of the Federation of Rhodesia and Nyasaland ordered the construction of the dam over sixty years ago and holds 185 cubic kilometres of water. It generates electricity for parts of Zambia and Zimbabwe. Routine monitoring of the dam highlighted the requirement for refurbishment. The Kariba Dam Rehabilitation Project will focus on two areas. Firstly, the refurbishment of the spillway and, secondly, the reshaping of the plunge pool.

The spillway consists of six sluice gates which enable the operators to release water from the dam to manage the water levels. However, when exposed to water, concrete undergoes minor expansion. After decades of operation, the dam is approaching a point where this expansion could affect the smooth operation of the sluice gates.

As water gushes from the Kariba Dam’s spillways, it enters the waters below. The sheer force of the cascading water creates erosion on the river bed. Over time, this erosion has created a deep pool at the base of the dam. Given that, there is potential for the erosion to reach the dam’s foundations with the inevitable consequences. In light of this, the plunge pool wall will be re-enforced.

The Spillway Refurbishment

Aquaforce Concrete Services will support Freyssinet International with the huge task of removing 1,000m3 of concrete from the dam’s six sluice gates.

Aquaforce will carry out hydrodemolition to remove the concrete without damaging the underlying rebar or the surrounding metal infrastructure. Hydrodemolition uses a high pressure jet of water at a pressure, normally above 1000 bar, enabling concrete removal faster than using a jackhammer. Significantly, this process of concrete removal does not affect the underlying metal rebar. Furthermore, the mechanical impact of a jackhammer can cause small cracking in the surrounding healthy concrete. Hydrodemolition, on the other hand, affects only the concrete that it comes into contact with.

The vibrations jackhammer users will be all too familiar with are almost eliminated when using high pressure water jetting; Recent Hand Arm Vibration (HAV) legislation has led to a huge increase in the use of high pressure water jetting for concrete removal applications. Furthermore, with hydro demolition, operators benefit from reduced noise and dust. The finish achieved with hydrodem gives a surface which is ideal for bonding between old and new concrete. In addition to the benefits already mentioned, hydro demolition is, quite simply, much quicker than traditional techniques.

Check out this hydrodemolition case study.

The Equipment

The project will require both manual hand lance and robotic methods of concrete removal. Calder will supply the high pressure pumping and filtration equipment. The Calder scope of supply does, therefore, include:

2 x Containerised Pump Units

Each unit is mounted into a noise-attenuated container and features the Hammelmann HDP500 series reciprocating plunger pump. Driven by a Volvo engine, each unit will deliver 262 lpm at 1040 bar.

2 x Trailer Pump Units

We mount these units onto road-going running gear. A Cummins diesel engine drives the Hammelmann 200 series pump and each unit has a performance of 110 lpm at 1000 bar.

2 x Containerised Water Filtration System

A filtration system cleans the water used in the Kariba Dam Rehabilitation Project hydrodemolition process. The system cleans the water to a quality that will allow the operator to return the water to its source, in this case back to Lake Kariba. Alternatively, the water can be re-used in the ongoing hydrodemolitoion works.

Operation and Maintenance Training

The project’s scope of supply includes operation and maintenance training. Our Life Cycle Services team offer familiarisation and training courses, and full service and spares support.

Get in Touch

To talk with a sales engineer about your application, please call +44 1905 751790 or sales@calder.co.uk.

See why operators choose our high pressure waterjetting equipment.