Challenging tasks ... cutting the foundation wall at the Jubail plant
Demolition expert knows the drill
German demolition expert Hermann Schutzeichel elaborates on two of the specialised jobs it has handled in Saudi Arabia.
01 MARCH 2001
Specialist demolition, construction and engineering company Hermann Schutzeichel GmbH recently completed two challenging projects in Saudi Arabia, adding to its record of accomplishments worldwide.
One of the projects involved partly demolishing a 1-m-thick concrete retaining wall by removing 20-m-long by 3-m-wide sections at a time, at a new steel fabrication plant in Jubail.
The other involved drilling four 800-mm-diameter cores through a 6-m-thick quay wall at Jeddah's port to facilitate the laying of a pipeline between a sugar mill and the harbour.
At the Jubail plant, Schutzeichel had to cut off only the top part of piles which formed the retaining wall, to facilitate widening its upper sections at a later stage. This required a systematic approach in order to be able to meet the deadline set by the main contractor.
The retaining wall for the foundation pit was solid and stable: it had been installed by drilling 40-m-deep overlapping boreholes into the outer edge of the foundation and casting them with concrete. To withstand earth pressures, every second pile had been reinforced with 20-mm-thick steel rebar. Overlapping piles and additional anchoring of the back wall in the foundation soil had resulted in a very stable and relatively watertight retaining wall.
Demolition was carried out by using a totally vibration-free diamond wire saw, in order not to risk the ingress of groundwater into the foundation. It also enabled the company to complete the job within 14 days without hindering other work under way on the project.
About 100 linear m were removed from the concrete retaining wall cutting to a depth of 12 m. Because of the limitations set by the crane available on site, the wall had to be cut into 20-m-long sections so that the weight of each individual section would not exceed the maximum capacity of the crane.
''A 40-m-long diamond wire was used to cut the concrete piles, driven by a 22 kW hydraulic power pack. Holes were drilled into each individual section after they had been cut to facilitate their removal by crane. Using a diamond wire made in Germany, a cutting rate of 10 sq m per day was achieved, enabling the work to be completed on schedule after 10 days.
The Jeddah project involved work on new raw sugar processing plant in a modern industrial complex adjacent to the port and associated facilities.
''In order to increase the speed at which ships could be unloaded, it was decided to lay a pipeline direct from the processing plant to the harbour, which, as required, could be connected to the cargo ships," recalls Klaus Schutzeichel, general manager of the company. "The pipe also had to pass through the 6m-thick wall of the quay. The contract required four 800 mm diameter cores to be drilled through the wall with the work on the seaward side having to be carried out 7 to 8 m below sea level. Maximum permitted deviation from the horizontal could be no more than 2 cm.
"A further difficulty was that the quay wall itself consisted of precast concrete elements, each having a 2-m-wide cavity. In order to prevent the entire wall from sinking, it was absolutely essential to ensure that the bores were made through the cavities."
In order to secure the guide frame for the drill bit to the seawall, four 30-mm-diameter anchoring holes were first drilled into the wall and M16 anchoring bars inserted. The 400 kW drive unit, built by Schutzeichel, was located on the quayside. A 500-mm-diameter diamond bit was used in the first stage of the work, first drilling to a depth of 1 m. After removing the core, drilling was continued into the cavity with the same diameter drill. Subsequently, using a different drill bit, each borehole was produced to its final size of 800 mm. All the drilling work was carried out at a rotational speed of 90 rpm. Despite the unusual operating conditions the work was completed within 10 days to the complete satisfaction of the main contractor.
Herman Schutzeichel, based in Strassenhaus, Germany, specialises in coredrilling (up to diameters of 1,500 mm), wall-saw cutting (up to diameters of 2,500 mm), diamond wire cutting, circlesawing (up to diameters of 3,500 mm) and joint cutting on roads and runways. The company's activities also include lighting of airport runways and the production and distribution of machineries and diamond tools.
