Regional Report: DFI Middle East Gulf Region Geotechnical Challenges The Gulf Region offers a vast variety of challenging geotechnical subsurface conditions including shallow weak carbonate rock (UAE and Gulf seabed) to strong to very strong rock (Qatar); problematic loose sand and soft cohesive soils (UAE, Saudi and Kuwait); deep very soft clays (Iran shores); highly aggressive groundwater and soils (throughout the region); and coral reefs (Saudi Arabia). All of these interesting profiles, combined with the significant structures and high-rise towers being built in the region, pose various geotechnical challenges in terms of design and construction. Khaldoun Fahoum, Ph.D., P.E., Chair DFI Middle East, Vice President/Middle East Regional Manager – Langan International DFI Middle East continues its successful journey into 2012. With many events and increased member ship s ince i t s establishment in 2009, DFI Middle East elected a new regional committee at the beginning of 2012. The new committee consists of Khaldoun Fahoum, Ph.D., P.E. as the new chair; Erik Green, technical manager, Soletanche Bachy Middle East as vice chair; Salah Al Dilimi, Road and Transport Authority, as treasurer, Emad Sharif, Dubai branch manager, Arab Center for Engineering Studies, as secretary; as well as Mamdouh Nasr, Ph.D, P. Eng., as the past chair, who had tremendous influence and effort in the establishment of the regional committee. DFI Middle East kicked off this year with a successful deep foundations conference at the American University in Dubai. Our plans for this year include dewatering seminars in Dubai and Abu Dhabi, as well as a foundations conference in Cairo early next year. This article provides a quick review of the various challenges in the areas of deep foundations and shoring, problematic soils and ground improvement and corrosion protection in the Gulf Region. Shoring and Deep Foundations Increasing urbanization in the Middle East has led to an increased demand for excavation support for basement construction and deep foundations for high-rise buildings. A large part of the urban centers are concentrated along the coasts and typically ground conditions in these areas combine overburden soils and high water tables. Temporarily cased bored piling (drilled shafts or caissons) using digging buckets and rock augers for weak rock excavation is by far the most common form of deep foundation construction, and widespread in the region with a large range of both local and international contractors in the market. Although the Gulf Region has varying ground conditions, a typical soil profile consists of sand overlying weak rock, and so most structures with significant loads or that are sensitive to movement will be founded on deep bored piles that derive their resistance from skin friction in rock. Most of the deep foundation practitioners also provide shoring solutions for the construction of underground spaces, typically for basements or roads and railways. Traditionally, most shoring has used cased bored piling equipment for piled walls (contiguous, secant and soldier walls) but with increasing population density and depth of basements (6 basements and deeper are becoming more common). Also, there is a growing awareness of the impact of dewatering on adjacent properties. More sophisticated techniques are being introduced such as slurry diaphragm walls. The Dubai Metro in particular can be singled out for specifying and successfully implementing permanent diaphragm walls and has become a reference in the region. The upcoming Doha Metro will surely contain a variety of shoring techniques. Problematic Soil Conditions and Ground Improvement The most commonly encountered problematic conditions encountered in the Gulf Region are the locally known “Sabkha” soils, which are very loose/very soft fine silty sands/silts/clays associated with high groundwater conditions, sometimes with thickness of up to 15 m (49 ft). Loose sands (sand dunes) are also often encountered inland with significant thickness. Sabkhas are mostly encountered near shore line areas. In these arid environments, highly expansive dry clays/claystone and soils with high collapse potential/high water soluble salts content are also encountered frequent ly. Ground improvement techniques are often utilized to enable construction on sites with problematic soils. These techniques include dynamic compaction and replacement, stone columns and vibroflotation, remove/replace, grouting, preloading, dynamic surcharging and regular surcharging, and soil mixing. The following describes problematic soils in one of the sites in the Sultanate of Oman. Problematic soil conditions found at the proposed Duqum Port Roads Project in the Sultanate of Oman, posed a challenge and impacted the time schedule and the cost of the project. The project lies near the coast of the Gulf of Duqum, where a new port is being established. A network of about 40 km (25 mi) of roads with embankments up to 5 m (16 ft) in height and 40-60 m (131-197 ft) wide, drainage ditches and large drainage canals are included in the project. DEEP FOUNDATIONS • SEPT/OCT 2012 • 21
