Analytical Model for Pullout Capacity of a Vertical Concrete Anchor Block Embedded at Shallow Depth in Cohesionless Soil

Helical nails are a new alternative to conventional soil nails or tie-backs for stabilization of slopes, excavations, and embankments due to ease of installation, minimal site disturbance, and immediate loading capability. Pullout capacity of helical nails is a critical parameter for their design. This study investigates the pullout behaviour of helical soil nails installed in dry dense sand through a series of laboratory tests. The tests were performed on seven different types of helical nails in a displacement-controlled manner. The paper describes the test procedure, results and highlights the influence of different parameters on the pullout capacity. Results show that roughness of the nail shaft significantly influences the peak pullout capacity of helical soil nails. A linear relationship between peak pullout force and overburden pressure is observed for different types of helical soil nails, indicating that it satisfies the Mohr–Coulomb failure criteria. A helical soil nail having a double helix of unequal diameter and the same interspacing shows higher pullout capacity than a helical soil nail having a double helix of the same diameter. The position of the helix and spacing-to-diameter ratio of the soil nail with a double helix of unequal diameter plays a significant role on the peak pullout capacity.

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Numerical Investigation Into the Keying Process of a Plate Anchor Vertically Installed in Cohesionless Soil

Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics ◽

10.1115/omae2018-78617 ◽

2018 ◽

Author(s):

Nabil Al Hakeem ◽

Charles Aubeny

Keyword(s):

Peak Load ◽

Offshore Structures ◽

Cohesionless Soil ◽

Soil Conditions ◽

Embedment Depth ◽

Pullout Capacity ◽

Vertical Loading ◽

Wide Range ◽

Plate Anchor ◽

Plate Anchors

Vertically driven plate anchors offer an attractive anchoring solution for floating offshore structures, as they are both highly efficient and suitable for a wide range of soil conditions. Since they are oriented vertically after installation, keying is required to orient the anchor into the direction of applied loading. Simulation of the keying process has not been extensively investigated by previous research, especially for cohesionless soil. Reliable prediction of irrecoverable embedment loss during keying is needed, since such loss can lead to significant reduction in the uplift capacity of the plate anchors. Large deformation finite element analyses LDFE method using RITSS (Remeshing and Interpolation Technique with Small Strain) were used to simulate the keying process of strip plate anchor embedded in uniform cohesionless soil. LDFE showed that the loss in embedment depth of plate anchor during rotation is inversely proportional to the loading eccentricity e/B. It was also found that the maximum pullout capacity occurs before the end of keying process at orientations between 60° to 85° degrees for vertical loading. Also, the LDFE study showed that reduced elastic soil stiffness leading to increased levels of displacement at which the peak load is approached.

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