A Unified Model for Analyzing Comprehensive Behaviors of Deepwater Anchors

Anchors may exhibit various complicated behaviors in the seabed, especially for deepwater anchors including gravity installed anchors (GIAs) and drag embedment plate anchors (drag anchors), stimulating the development of an efficient analytical tool that applies to a variety of anchors. The present paper introduces a unified model for analyzing different anchor behaviors in both clay and sand, consisting of unified concepts, mechanical models, and analytical procedure. The kinematic behaviors of the anchors are classified uniformly as three types, i.e., diving, pulling out, and keying. By utilizing the least-force principle, various anchor properties, such as the ultimate pullout capacity (UPC), failure mode, movement direction, embedment loss, and kinematic trajectory, can all be determined by the combination and analysis of the three behaviors. Applications of the model are demonstrated summarily, by solving the UPC and the failure mode of anchor piles and suction anchors, the kinematic trajectory of drag anchors in a single soil layer or layered soils, the maximum embedment loss (MEL) of suction embedded plate anchors (SEPLAs) and OMNI-Max anchors, and the kinematic behavior of OMNI-Max anchors. Compared to existing theoretical methods, this unified model shows strong applicability and potentiality in solving a variety of behaviors and properties of different anchors under complicated seabed conditions.

Ultimate Pullout Capacity of a Square Plate Anchor in Clay with an Interbedded Stiff Layer

Three-dimensional nonlinear numerical analysis is carried out to determine the ultimate pullout capacity of a square plate anchor in layered clay using the large finite element analysis software ABAQUS. An empirical formula for the pullout bearing capacity coefficient of a plate anchor in layered soils is proposed based on the bearing characteristics of plate anchors in single-layer soils. The results show that a circular flow (circulation field) is induced around the plate anchor during the uplift process and that the flow velocity and circulation field range are mainly affected by the properties of the soil around the plate anchor. The bearing characteristics of plate anchors in layered soils are influenced by factors such as the embedment depth of the plate anchor, the friction coefficient between the soil and the plate anchor, the thickness of the upper soil layer, and the thickness of the middle soil layer. The rationality of the finite element numerical calculation results and the empirical formula is verified by comparing the results from this study with results previously reported in the literature.

Behaviour of Granular Anchor Pile (Gap) and Group Piles in Different Type of Soils under Vertical Pullout Loads

In the present study, the load displacement behaviour of Granular Anchor Pile (GAP) and Group piles under vertical pullout loads in two different type of cohesionless soils have been investigated. The main objective of the study is to investigate the effect of embedment length, diameter and spacing varying (L/D and S/D ratio) on Pullout Capacity of Granular Anchor Pile system in different type of soils. GAP pile is innovative and effective in resisting the uplift pressure exerted on the foundation. Based on the laboratory study on single and group of 2 and 4 GAP systems, it is found that the ultimate Pullout Capacity of single GAP system increases with the increase in length (L) to diameter (D) ratio in both type of soils. The rate of increase of ultimate pullout capacity of single GAP systems having 50 mm diameter and 100 mm diameter was significant up to increase in L/D ratio of 39%. Thus, it was inferred that for single GAP system, there is maximum advantage upto L/D ratio 10.50 for 50 mm and 7.00 for 100 mm. In case of medium dense soil with higher relative density, the increase in pullout capacity is more as compared to loose soil with lower relative density. It was further confirmed that ultimate pullout capacity is a function of diameter of GAP and soil characteristics. The ultimate pullout capacity of group of 2 and 4 GAP systems with 100 mm diameter was found to increase with S/D ratio upto 3.00 and 2.75 respectively only in both the soils.