Student Paper Competition Winner: Investigation of Vibratory Hammer Installation for Deeply Embedded Ring Anchor System in Sand-PPT Presentation

PPT Presentation

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This study evaluates whether a deeply embedded ring anchor (DERA) can be installed in sand—and its follower extracted—using a vibratory hammer. Compared with large suction caissons, DERAs are smaller, simpler, and potentially less costly, while vibratory installation is suitable for sandy soils.<br /><br />The proposed model treats the DERA–follower system as a pile and predicts whether vibration will produce sufficient cyclic shear strain in the surrounding soil to enable penetration. Finite-element analyses were used to estimate soil–structure stiffness and damping, and installation was assumed possible when cyclic strain reached a threshold of 0.02%. The model was checked against two reported vibratory pile-driving cases, with differences attributed to uncertainties in soil properties and the assumed strain threshold.<br /><br />The model was applied to three sand conditions, from medium dense to very dense, for DERAs 2.5–2.9 m in diameter and embedded 37.5–43.5 m. Results indicate that required hammer size increases with sand density and decreases as operating frequency rises. At frequencies of 20 Hz or higher, the predicted eccentric moment needed for installation is no more than 0.3 tonne-m, within the capacity of commercially available equipment. Follower extraction requires a slightly larger hammer than installation but is also feasible with standard equipment.<br /><br />The findings support the technical feasibility of vibratory installation and extraction of the DERA–follower system in sand. Further work is recommended on other soil profiles, including clay and interbedded deposits, and on the long-term fatigue effects of vibration-induced stresses.

Keywords

deeply embedded ring anchor

DERA

vibratory hammer

sand installation

follower extraction

cyclic shear strain

finite-element analysis

pile driving

soil stiffness and damping

anchor feasibility