The pumping station will be the world’s second deepest. It has a screen shaft and two pumping shafts, each of which has a total drop of more than 72m into the ground. There is also a three-stage collection chamber, various auxiliary buildings and permanent site offices.
It is designed to deal with growing demand as Jeddah’s population rises and is part of a US$1.1bn investment programme funded by Saudi Arabia’s National Water Company. Construction is expected to be completed in June 2013. Once operational, the Pumping station is designed to pump a maximum flow of 1,125,000m3 per day, ensuring enough capacity to cope with future predictions for population growth.
Each shaft is 68m deep. The screen shaft has a 4.5m thick concrete base slab and each pumping shaft has a 5.5m thick base slab. Before RMD Kwikform started supplying formwork, the contractor constructed the circular diaphragm walls using 2.4m concrete panels. Once excavated to full depth, the 1.2m shaft thick wall was constructed, followed in succession by the bottom slab.
Mohammed Asif from RMD Kwikform said: “When we were faced with the shoring challenge of supporting a slab 68m high, but underground in a confined space with very little room to play with, we recognised there were two key hurdles to the project, the first being safety and the second logistics. Having had previous experience using Rapidshor on major bridge projects, we knew the equipment was structurally capable of dealing with the load, and due to it being a modular system, installation was more straightforward within the confines of the shafts."
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There were three main formwork elements of the project that RMD Kwikform was involved in, including supplying double-sided wall formwork to the U-shaped collection chamber building. Using a range of equipment, including steel Superslim Soldiers as primary beams and Alform beams as secondaries, the wall formwork reached a total height of 13m. The entire structure above ground level was poured in a single pour, using a total volume of 3,100m3 of concrete.
Rapidshor shoring with U-heads and Alform beams were also used to support 500mm-thick concrete slabs on top of the three 46m-diameter shafts. The Rapidshor was built 68m high and topped with U-heads, which held double Alform beams as primary bearers and single Alform beams as secondaries.
In order to support the slab construction, each shaft was lined with over 10,255m3 of Rapidshor shoring. This was built up into a birdcage structure, securely tied into the main concrete walls and laced together to form a shoring solution capable of supporting the construction of drop beams and the capping slab of each shaft.
The 2,000mm-deep, 600mm-wide, 5,000mm-long drop beams were constructed using Superslim Soldier primary beams and Alform secondary beams, with the slab support constructed using Alform beams. The 500mm-deep capping slabs were then poured in order to partially cover the shafts. The cover slabs will go on to form part of the ground floor of permanent site offices, due to be built towards the end of the project.
The third part of the construction that RMD Kwikform assisted with was to supply a Rapidclimb and Maxima wall formwork panel system for the 500mm-thick internal walls, required for the lift core walls, stairwells and offices for two of the shafts.
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