North Jeddah for STP

Contractor Abuljadayel Co, specialists in the field of water and waste water projects, has utilised a number of formwork and shoring solutions provided by RMD Kwikform to support the construction of the World's second deepest pumping station at the North Jeddah Pumping station project in Saudi Arabia.

Designed to deal with the increased demands of the growing population of Jeddah, the new facility is part of a $1.1bn investment programme funded by Saudi Arabia’s National Water Company. The North Jeddah pumping station facility comprises of a screen shaft and two pumping shafts, all of which drop over 72 metres in total into the grounds. There is also a three-stage collection chamber, various auxiliary buildings and permanent site offices.

Each shaft is 68 metres deep. The screen shaft has a 4.5 metre thick concrete base slab and each pumping shaft has a 5.5 metre base slab. Before RMD Kwikform started supplying formwork, the contractor constructed the circular diaphragm walls using 2.4 metre concrete panels. Once excavated to full depth, the 1.2 metre thick shaft wall was constructed, followed in succession by the bottom slab.

Formwork elements

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 13 metres. With 348 linear metres of equipment being used for this section of the construction, 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 used to support 50mm thick concrete slabs on top of three 46 metre diameter shafts. The Rapidshor was built 68 metres high and topped with U-heads, which held double Alform beams as primary bearers and single Alform Beams as secondary’s

Commenting on the project, Mohammed Asif from RMD Kwikform said:

When we were faced with the shoring challenge of supporting a slab 68 metres 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. 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 Beams. The 50mm 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.

Mohammed Asif continued:

The main engineering challenge was how to tie the system together and install safe access for the workers. It was for this reason that as part of the solution we supplied onsite technical assistance in the shape of two site operatives. One of the technicians remained onsite with the ground team from start to finish, with an additional team member supporting the training and erection programme devised for the customer.

The third part of the construction that RMD Kwikform assisted with was to supply a Rapidlcimb 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. In order to provide an efficient and safe solution, RMD Kwikform recommended a combination of Maxima modular wall formwork and Rapidclimb climbing formwork. The panel system approach was specified by the contractor, having seen the capabilities of Maxima.

The RMD Kwikform Rapidclimb system was used inside two of the pumping shafts to provide wall formwork to the lift-shaft cores and internal walls. Rapidclimb is a crane assisted climbing formwork system that provides safe, self contained working levels for economical core and wall forming. It also features a rack and pinion activated mechanism with a wedge-locking device for securing the position of the shutter. The climbing bracket can achieve up to 45kN maximum vertical capacity.

Mohammed Asif continued:

When we were faced with the core formwork challenge, we saw it as an opportunity to utilise the capabilities of Maxima as the wall formwork system. It has been used extensively in similar projects across the globe, so we were confident it was the right solution to overcome the challenges posed by this project. By reusing the Maxima Panels for each of the 24 pours required for the formation of the core, significant time and cost savings benefits were released.

Mohammed Rateb Jawish from Abuljadayel co. said:

The tight programme time required us to think carefully about the solution we required for the formwork and shoring parts of the project. Using a modular panel system, such as Maxima allowed us to complete the whole core construction efficiently and to a high quality standard. The time and cost saving benefit we saw certainly showed the advantages of utilising a panel systems on this type of project.

Once operational, the pumping station is designed to pump a maximum flow of 1,125,00m³ per day, ensuring enough capacity to cope with future predictions for population growth.