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

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Tugen Feng ◽  
Jingyao Zong ◽  
Wei Jiang ◽  
Jian Zhang ◽  
Jian Song
Keyword(s):  
Finite Element ◽  
Empirical Formula ◽  
Soil Layer ◽  
Embedment Depth ◽  
Layered Soils ◽  
Pullout Capacity ◽  
Plate Anchor ◽  
Square Plate ◽  
Plate Anchors ◽  
Ultimate Pullout Capacity

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.

scholarly journals A Unified Model for Analyzing Comprehensive Behaviors of Deepwater Anchors

2021 ◽  
Vol 9 (8) ◽  
pp. 913
Author(s):  
Haixiao Liu ◽  
Yancheng Yang ◽  
Jinsong Peng
Keyword(s):  
Failure Mode ◽  
Soil Layer ◽  
Unified Model ◽  
Movement Direction ◽  
Layered Soils ◽  
Pullout Capacity ◽  
Kinematic Behavior ◽  
Mechanical Models ◽  
Plate Anchors ◽  
Ultimate Pullout Capacity

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.

scholarly journals Finite-Element Analysis of Keying Process of Plate Anchors in Three-Layer Soft-Stiff-Soft Clay Deposits

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Tugen Feng ◽  
Huajiao Xu ◽  
Jian Song ◽  
Jian Zhang ◽  
Mi Zhou ◽  
...  
Keyword(s):  
Finite Element ◽  
Soft Clay ◽  
Soil Layer ◽  
Three Dimensional ◽  
Embedment Depth ◽  
Element Analysis ◽  
Clay Deposits ◽  
Local Soil ◽  
Plate Anchors ◽  
Stiff Soil

This paper presents the results from numerical modeling of the keying process of plate anchors in three-layer soft-stiff-soft clay deposits. Three-dimensional large deformation finite-element analyses were carried out, and the results were firstly validated by the centrifuge test data and the previous numerical results. The soil flow mechanism during the keying process of plate anchors was examined, and a series of parametric studies were performed to investigate the factors affecting the rotation characteristics of plate anchors with an emphasis on the presence of the interbedded stiff soil layer. The results indicate that the loss of embedment depth of plate anchors decreases with the increase of the thickness of the first soil layer when the anchor is initially located at the middle of stiff soil layer. The flow velocity of soil around the anchor that is initially embedded at the first layer and adjacent to the underlying interbedded stiff soil layer is generally larger, resulting in a smaller embedment depth loss compared with the traditional normally consolidated soil layer. The interbedded stiff soil layer affects the keying process of plate anchors embedded 1.0B above and 2.0B below the interbedded stiff soil layer (B is the width of the square plate anchors). The increase of the strength of local soil around the plate anchors leads to the increase of the embedment depth loss, but the increase of the strength of soil slightly away from the plate anchors leads to the decrease of the embedment depth loss.

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

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.

The ultimate pullout capacity of anchors in frictional soils

2006 ◽  
Vol 43 (8) ◽  
pp. 852-868 ◽  
Author(s):  
R S Merifield ◽  
S W Sloan
Keyword(s):  
Finite Element ◽  
Lower Bound ◽  
Limit Analysis ◽  
Numerical Study ◽  
Past Research ◽  
Pullout Capacity ◽  
Current Design ◽  
Pullout Load ◽  
Ultimate Pullout Capacity ◽  
Frictional Soils

During the last 30 years various researchers have proposed approximate techniques to estimate the uplift capacity of soil anchors. As the majority of past research has been experimentally based, much current design practice is based on empiricism. Somewhat surprisingly, very few numerical analyses have been performed to determine the ultimate pullout loads of anchors. This paper presents the results of a rigorous numerical study to estimate the ultimate pullout load for vertical and horizontal plate anchors in frictional soils. Rigorous bounds have been obtained using two numerical procedures that are based on finite element formulations of the upper and lower bound theorems of limit analysis. For comparison purposes, numerical estimates of the break-out factor have also been obtained using the more conventional displacement finite element method. Results are presented in the familiar form of break-out factors based on various soil strength profiles and geometries and are compared with existing numerical and empirical solutions.Key words: anchor, pullout capacity, finite elements, limit analysis, lower bound, sand.

NORMALLY LOADED INCLINED STRIP ANCHORS IN COHESIONLESS SOIL

2020 ◽  
Author(s):  
Nabil Al Hakeem ◽  
Charles Aubeny
Keyword(s):  
Finite Element ◽  
Scale Effects ◽  
Orientation Angle ◽  
Cohesionless Soil ◽  
Limited Attention ◽  
Embedment Depth ◽  
Finite Element Analyses ◽  
Dense Sand ◽  
Full Characterization ◽  
Plate Anchors

Plate anchors are among the most effective anchorage systems that are widely used to resist horizontal and inclined uplift loads in many offshore and onshore applications. Previous research on plate anchors has largely focused on the horizontal or vertical breakout problems, with limited attention directed towards obtaining a full characterization of the effects of anchor orientation angle. The present study utilizes displacement-based finite element analyses to investigate the stability and performance of strip anchor embedded in cohesionless soil for plate inclination angles ranging from 0o to 90o from horizontal, where the applied load is normal to and acts at the center of the plate. This study investigates the effects of scale and roughness, along with the geometry of the failure mechanism for various plate orientations and embedment depths. The analyses, presented in terms of a non-dimensional breakout factor Nq, show that the breakout factor increases significantly with an increase in the inclination, especially for angles greater than 45 degrees in loose sand and greater than 60 in dense sand. The analyses also show that scale effects (anchor width) can affect capacity. Finite element analyses have been used to introduce simple design charts relating the breakout factor to the embedment depth and relative density. Comparisons to experimental and numerical studies showed good agreement.

scholarly journals Design and analysis of plate anchors in sand

2021 ◽  
Author(s):  
Muhammad Waseem
Keyword(s):  
Failure Modes ◽  
Design Procedure ◽  
Embedment Depth ◽  
Offshore Platforms ◽  
Failure Plane ◽  
Transmission Towers ◽  
Plate Anchor ◽  
Plate Anchors ◽  
Anchor Design ◽  
Uplift Forces

Plate anchors, as an efficient and reliable anchorage system, have been widely used to resist uplift forces produced by structures, such as transmission towers, offshore platforms, submerged pipelines, and tunnels. In order to design a plate anchor it is important to know the factors which influence the design and uplift behavior of anchors embedded in sand. In this report a number of model uplift tests and numerical investigations made by different authors are described and based on these readings the uplift behavior of anchors in sand is explored and anchor's design procedure is described. In addition, basic anchor types, failure modes in anchors, and design codes are mentioned. Based on this study, it is found that the failure plane and uplift capacity is significantly influenced by the soil density and embedment depth. Therefore, it is concluded that the influence of sand density and embedment depth should be considered in anchor design.

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