Suction Anchors In Clay Research Articles

Holding capacity of suction anchors under combined loading

This paper introduces a numerical investigation aimed at evaluating the Vertical, Horizontal, and Moment (VHM) yield surface of suction anchors. It employs a generalized elliptical function guided by a predefined fitting strategy. The resulting yield surfaces are then juxtaposed with findings from previous studies, establishing the groundwork for the macro model of suction anchors in clay. This model plays a pivotal role in the integrated analysis of mooring systems for floating wind turbines.

Inclined Pullout Capacity of Suction Anchors in Clay over Silty Sand

This study presents a range of numerical modeling to evaluate the pullout capability of suction anchors subjected to inclined mooring loading in a clay-over-silty-sand deposit. Comprehensive numerical models were generated, which were validated against existing centrifuge testing and numerical modeling results. A parametric study was then carried out to assess the effects of the anchor length, padeye location, mooring angle, and layered deposits on the pullout capacity of suction anchors. According to the numerical simulation results, the following key design factors were obtained: (1) the optimal padeye position, (2) the ultimate horizontal and vertical pullout abilities, and (3) the horizontal load distributions at different padeyes. A simple framework of calculating the combined VH surfaces of the anchors was developed for preliminary prediction of the pullout capacity of suction anchors in a clay-over-silty-sand deposit that provides the optimized location of padeyes and more accurate prediction for the holding capacity of anchor. The design method proposed by this study can contribute to optimize and improve the current design guideline for more accurately predicting the bearing capacity of anchors in clay-over-silty-sand soil deposits.

Discussion of “Effects of misalignment on the undrained HV capacity of suction anchors in clay” by A. Saviano and F. Pisanò

This discussion is based on the paper by Saviano and Pisanò (2017) (hereafter identified as “the original authors” or “the original paper”). The original authors employed a three-dimensional finite element analysis to investigate the effects of misalignment on the undrained capacity of suction anchors subjected to horizontal (H) and vertical loadings (V). In the original paper, various parametric studies including the misalignment angle, the anchor aspect ratio, the soil strength profile, and the interface adhesion factor on the HV failure envelope of suction anchors were comprehensively carried out. The discussion addresses the issues of the three-dimensional modelling approach for suction anchors using the model of the single anchor/plug rigid body employed in the original paper and questions the validity of the model if it corresponds to the most accurate representation of the numerical model for this type of offshore foundation.

Effects of misalignment on the undrained HV capacity of suction anchors in clay

Suctions anchors are widely employed to connect offshore floating structures to the seabed, and in particular to withstand the horizontal-vertical (HV) loads transmitted through inclined moorings. Imperfections during suction installation may cause anchor misalignment (or misorientation): this term denotes the line of action of the applied force not passing through the vertical axis of the anchor, and thus resulting in additional torsion during operations.The outcomes of a finite element (FE) investigation on the effects of misalignment are reported, with specific reference to the undrained HV capacity of suction anchors in soft clay. The changes in HV failure envelopes due to spurious torsion are described over a large misalignment range, in combination with varying geometrical/mechanical factors.Based on fundamental understanding of “misaligned” soil-anchor interaction, new algebraic expressions are provided for practical capacity assessment. A further simplified methodology is also proposed for the most common case of low misalignment.

A Comparison of Pull-Out Capacity of Suction Anchors in Clay and Sand

With the oil and gas exploitation develop to the deep sea; offshore platform under extreme environment load needs more stable anchorage foundation. Based on the slender suction anchor of SPAR, three-dimensional numerical analysis method was presented to study the ultimate pull-out capacity. Based on the geological conditions from South China Sea, clay and sand was selected as soil conditions to make a comparison analysis. The effects of soil type, load positions, load angles and aspect ratio on the ultimate bearing pull-out resistance of the suction foundation were studied. The comparison analysis results indicated that the ultimate pull-out resistance of suction anchors in sand has a greater rise rate and achieve ultimate pull-out capacity need smaller displacement than in clay; load point and load angles have a great impact on the resistance and there is a critical aspect ratio under inclined loading in sand.

Analytical study of the failure mode and pullout capacity of suction anchors in clay

Suction anchors are widely adopted in mooring systems. However there are still challenges in predicting the failure mode and ultimate pullout capacity of the anchor. Previously published methods for predicting the inclined pullout capacity of suction anchors are mainly based on experimental data or the FEM analysis. In the present work, an analytical method that is capable of predicting the failure mode and ultimate pullout capacity of the suction anchor in clay under inclined loading is developed. This method is based on a rational mechanical model for suction anchors and the knowledge of the mechanism that the anchor fails in seabed soils. In order to examine the analytical model, the failure angle and pullout capacity of suction anchors from FEM simulation, numerical solution and laboratory tests in uniform and linear cohesive soils are employed to compare with the theoretical predictions and the agreement is satisfactory. An analytical method that can evaluate the optimal position of the attachment point is also proposed in the present study. The present work proves that the failure mode and pullout capacity of suction anchors can be reasonably determined by the developed analytical method.

Horizontal Capacity of Embedded Suction Anchors in Clay

The embedded suction anchor (ESA) is a type of permanent offshore foundation that is installed by a suction pile. The primary factors influencing the horizontal pullout capacity of an ESA include the loading point, the soil type, the embedment depth, and the addition of flanges. The main purpose of this study is to develop an analytical solution that is capable of estimating the horizontal pullout capacity of ESAs with the loading point being anywhere along its length with or without flanges. An analytical solution has been developed to estimate the horizontal pullout capacity of embedded suction anchors in clay seafloor. Validation has been made through comparisons with the centrifuge model test results. Results indicate that the horizontal pullout capacity of the embedded suction anchor in clay increases, reaches its peak, and then starts to decrease as the point of the load application moves downward. The effect of flanges on the horizontal pullout capacity is also found to be significant. The horizontal pullout capacity is a direct function of the loading point. The horizontal pullout capacity increases as the loading point moves downward and the maximum pullout capacity is obtained when the loading point is approximately at the mid-depth. The increase in horizontal pullout capacity can be significant, i.e., more than twice in magnitude when the maximum pullout capacity is compared with that associated with the loading point near the top or tip.