ABSTRACT

Suction piles fabricated with glass fiber-reinforced plastic (GFRP) have been regarded as alternatives to conventional steel or reinforced-concrete suction piles to reduce the transportation cost and corrosion risk. However, difficulty may arise in suction installation due to the small weight of the GFRP pile. In this study, a concrete pile cap was attached to the top of the GFRP pile to add weight for aiding the suction installation. The field applicability of the GFRP suction pile was verified by performing field tests on suction installation. Results obtained from the field test showed that the GFRP suction pile was stable during penetration.

INTRODUCTION

Many offshore structures have been constructed for offshore space utilization, offshore wind turbines, and marine resource development in Korea. A suction pile is a circular surface foundation with thin skirts around its circumference. Suction piles can be installed economically and efficiently into soil deposits in deep water and have been used extensively in offshore facilities. The length-to-diameter ratio (L/D) of these piles does not exceed 6.0 (Randolph et al., 2005). The skirt of a suction pile penetrates the ground by pumping water out of the pile, which creates suction pressure inside it. The penetration force for pile installation is proportional to the pressure difference between the inside and outside of the pile and the section area of the pile; meanwhile, the penetration resistance is proportional to the pile diameter. Therefore, as the pile diameter increases, the pile can be easily penetrated with suction pressure inside the pile because the inner section area of pile is proportional to the square of the pile diameter.

According to a case study, the diameter of suction piles ranges from 3.5–44 m, pile length ranges from 4–36 m, and water depth is from 30-1,830 m. Suction piles are installed in various soil conditions, including soft clay and sand. However, the material of the suction piles is restricted only to steel or reinforced concrete (Andersen et al., 2005). Using steel or reinforced concrete for the production of suction piles requires securing a wide area for manufacturing. Transportation and installation cost significantly increase as the pile diameter increases due to the heavy weight of the materials. In addition, steel may suffer from corrosion problems caused by long-term exposure to seawater and bacteria (Tomlinson and Woodward, 2014). So it may not be suitable for repeated use, which is one of the important advantages of suction piles.

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