The results of several geotechnical studies performed for the Gulf of Suez Petroleum Company (GUPCO) in their Gulf of Suez July field are presented here. Soils at the site primarily consist of weak to moderate cemented carbonate sands and silts (carbonate content in excess of 90 percent). Pullout test results for 24-inch diameter pipe piles in this deposit illustrate that the current state-of-the-art practice in predicting soil pile response of driven pipe piles in calcareous deposits is not adequate. This study identifies the important geotechnical parameters and recommend at ions are provided to improve predictive capability in similar foundation environments.
Piles driven in calcareous sediments such as those encountered in the Gulf of Suez July field have been known to have significantly lower load capacity than would be predicted from conventional classical theory and limiting values for siliceous sediments (quartz sands). The large scale pile load tests in calcareous sands and silts offshore Australia illustrated this unique feature.
Twelve pullout tests were performed on five, 24 inch diameter pipe piles which were driven to penetrations from 25 feet to 100 feet (7.6 to 30.5 m) in the July field. A parametric study was performed to develop an understanding of soil-pile interaction in the calcareous sands and silts encountered there. This paper summarizes the findings of the study and presents recommendations for improved predictive procedures for frictional response of driven pipe piles in calcareous sands and silts.
The southern boundary of the GUPCO July field in the Gulf of Suez is approximately 6.2 miles (10 km) north of Ras Shukier, Egypt. The vicinity map for the area is shown on Figure 1. Geotechnical investigations for this field included five shallow borings to a penetration of 41 feet (12.5 m) and one deer boring which was drilled to a penetration of 302 feet (92 m) below the seafloor. One of the shallow borings was at the J-22 location and the remaining shallow borings were at J-8. The deep boring was drilled at the J-25 location. All samples from these borings were obtained with a 2 inch O.D. split-barrel sampler driven by a wire line percussion technique.
The pile test site is approximately 1 km southwest of the J-8 location. Five, 24-inch diameter pipe piles, all located within a radius of 500 feet (152.4 m), were tested for pullout capacity.
The carbonate sediments encountered in the July field are composed primarily of the skeletal remains of various microscopic plants and animals that thrive on the nutrients in the seawater. The common forms are the corral line algae and foraminifera. A generalized soil stratigraphy for the July field is shown on Figure 2. Fairly uniform conditions exist to a penetration of 46 feet (14 m) below the seafloor. These surface sediments essentially consist of carbonate sands which are weak to moderately cemented.
