Rashid Geotechnical & Materials Engineers (RGME), which introduced the Vibrex piling and ground improvement system to the Saudi construction industry in 1994, has over the years successfully worked on several projects in the Eastern Province and moved on to the country's western coast, while also being invited to participate in tenders for piling projects in Africa.

The company's services cover onshore and offshore geotechnical engineering, materials testing and quality control, check engineering, land and hydrographic survey engineering, GIS, digitised mapping including CADD services and software engineering, environmental and water resources engineering, NDT (non-destructive testing), corrosion control and cathodic protection and rehabilitation of structures including installation of mini and micro piles, says RGME-Piling manager Parvez Naushahi.

'After successful completion of large-size projects in the Eastern Province, Vibrex piles are also being used on coral soils of the western coast, in and around Jeddah,' says Naushahi. 'Apart from Vibrex piles and stone columns, RGME-Piling is carrying out specialised projects of sheet piling and dewatering works for deep excavations. RGME-Piling is also being invited by main contractors to participate in tenders involving economical systems of Vibrex piles for African countries.'

Detailing the features of the system, he says: 'Vibrex piles will provide up to 30 per cent savings compared to bored piles, for a given load capacity. The diameter ranges normally used for Vibrex piles are between 500 mm (20 inches) and 710 mm (28 inches). If loading configuration warrants use of larger diameter piles, we can use bored piles of up to 2 m diameter.

'Like bored piles, Vibrex piles are also cast in-situ concrete piles. These are constructed by first forming a hole in the subsurface soil by driving a closed-ended casing pipe and then filling it with reinforced concrete while simultaneously withdrawing the casing.

'Since Vibrex piles are large displacement-type piles, no soil is taken out from the ground, thus eliminating the problem of soil disposal. At the time of withdrawal of the casing, the concrete head will help to form an enlarged section of pile in loose and soft soil.

'This significantly increases the skin friction capacity of Vibrex piles, whereas in the case of bored piles the drilling process will cause the disturbance of in-situ soil, consequently reducing the skin friction capacity of the pile. The displacement technique associated with Vibrex piles also generates high end-bearing capacity as compared to the end-bearing capacity of bored piles.

'While driving the casing for Vibrex piles, a state-of-the-art, electronically controlled, hydraulic-impact hammer can be set to the required energy levels. The number of blows recorded for a specified driving interval will provide an 'instant quality check' on the pile capacity, which is not possible for bored piles.

'Vibrex piles are particularly suitable for the coral soils of the west coast, for example in Jeddah and the surrounding coastal areas.

'As a result of the pile-driving process, the granular nature of the coral soil will yield ground densification and in-situ compactness. This densification of the soil increases the shear strength parameters of the soil and provides higher load-carrying capacity to the pile. A typical soil profile of coral formation is shown in Figure 1, while full-scale pile load tests are in Figure 2. The load settlement curve shows little settlement at the test load, and it is evident from the test results that piles are providing higher safety factors than originally considered in the design of piles. Pile integrity tests have shown that the excellent quality of cast in-situ concrete up to the full depth of the pile.'

'RGME-Piling also installs H-piles and sheet piles using the same hydraulic impact driving system. These piling machines, having an electronically-controlled hydraulic energy system, are considered state-of-the-art in the industry,' says Naushahi. 'RGME Piling has also successfully completed offshore pile driving jobs of 1-m-diameter steel pipe piles.'

The Riyadh-based firm has seven branches in Saudi Arabia and also has branches in Qatar and Bahrain.