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Advancements in industry and increased energy demands have led to the construction of onshore and offshore platforms. The stability of these platforms is a major challenge for geotechnical engineers. Expandable anchors have recently been proposed to address this issue. Researchers have investigated the bearing capacity of anchors with different shapes and plate numbers using experimental and numerical methods. The use of a suitable method for numerical modeling of expandable anchors is necessary to determine their performance. The current study evaluated the bearing capacity of multi-plate anchors using the coupled Eulerian-Lagrangian, discrete element, and finite element methods and compares their results. The effect of an increase in the number of plates (to three), the distance between plates, the plate shape (square or circular), and the soil density (80% or 60%) on the bearing capacity of the anchors was determined. The results showed that the Eulerian model was in very good agreement with the experimental results and that the square anchor exhibited a higher bearing capacity than the circular anchor. An equation is proposed for the calculation of the bearing capacity of expandable anchors. [ABSTRACT FROM AUTHOR]

Abstract \nHighlights As the latest development and benchmark of a gravity installed anchor (GIA), the OMNI-Max anchor stands as a cutting-edge achievement and benchmark, finding increasingly widespread use within mooring systems due to its exceptional operational performance and adaptability. Notably, while investigations into the pullout capacity of OMNI-Max anchors have been conducted extensively in clay, the relevant studies are seldom observed in sand. Actually, the mechanical properties of sand are quite different from those of clay, and sand is also widely distributed in seabed soil. Full knowledge of OMNI-Max anchors not only in clay but also in sand is necessary to a wider application of the anchors. In the present work, the large deformation finite element (LDFE) method is adopted combined with the coupled Eulerian-Lagrangian (CEL) technique to study the end-bearing characteristics of the OMNI-Max anchor in sand seabeds. A bounding-surface plasticity model is taken as the constitutive model to capture the characteristics of sand. Through investigation and analysis, OMNI-Max anchors are closely related to the anchor embedment depth, the soil relative density, the anchor orientation, the loading angle and the bearing area, so the working conditions related to these five factors are designed and calculated. An explicit expression of the end-bearing capacity factor is finally derived to provide a simple and fast tool of evaluating the pullout capacity of the anchor in sand under multiple factors. Validation cases and orthogonal tests have confirmed the effectiveness and applicability of the explicit expression.LDFE analyses with CEL technique and bounding-surface plasticity constitutive modelAn explicit expression of end-bearing capacity factor for OMNI-Max anchors in sandEffectiveness and applicability of the expression confirmed by various waysPullout capacity property of OMNI-Max anchors in sand under multiple factorsA simple and fast tool of evaluating the pullout capacity of OMNI-Max anchors in sand [ABSTRACT FROM AUTHOR]

The critical penetration depth and failure displacement of vertically loaded anchor (VLA) have already been investigated. However, only few investigations focused on the double-plate VLA. Therefore, based on the finite element method, the critical penetration depth for the double-plate VLA was obtained, which is approximately 6.0 times the width of the upper fluke of the double-plate VLA. According to the reduced-scale model tests, the failure displacement of the double-plate VLA with different included angles and dimensions of the bottom fluke under shallow-embedded and deep-embedded conditions was obtained. Furthermore, the failure displacement of double-plate VLA with 30° included angle and the dimension of bottom fluke equal to that of upper fluke under shallow-embedded and deep-embedded condition is 0.29 and 0.67 times the width of upper fluke, respectively. Based on the empirical bearing capacity formula for VLA model, an improved bearing capacity formula for double-plate VLA model has been put forward; by means of the improved bearing capacity formula, the coefficient of bearing capacity for double-plate VLA under shallow-embedded and deep-embedded condition is obtained to be 5.013 and 4.106, respectively. [ABSTRACT FROM AUTHOR]

Many offshore and onshore platforms are constructed widely, especially in the energy supply sector. So far, various anchors with different shapes have been introduced for these applications to reinforce and stabilize the superstructures and related facilities. This study deals with the novel Expandable Multi-plate Mechanical Anchors (EMPMAs) and investigates their performance using physical modeling tests. Previous studies have focused on the behavior of single anchors, and there is no comprehensive experimental research on the multi-plate anchors, which is the subject of the present study. This research examines uplift capacity regarding the effect of five soil densities for loose, medium, and dense conditions and the vertical distance between two plate anchors from 0.5B to 2B. The obtained results were compared with the single plate anchor with equivalent areas. Based on the results, the highest bearing capacity is related to the EMPMA with an optimum distance of 1B in 80% relative density. In addition, by decreasing the distance between two plates, the relative density becomes a more dominant bearing capacity parameter. Furthermore, the Particle Image Velocimetry (PIV) method results are presented, and a new formula is proposed. Eventually, a comparative study is conducted between the results of PIV and an analytical formula. [ABSTRACT FROM AUTHOR]

This paper presents a limit equilibrium solution for calculating the ultimate pullout resistance of shallow vertical plate anchors in sand, considering the combined effects of anchor embedment ratio, sand shear strength, sand-anchor interface strength and anchor aspect ratio. The geometry of the failure mechanism in the solution reflects observations from model tests. The ultimate failure load of a strip plate anchor was then determined by global equilibrium analysis of the passive and active failure soil wedge. The two-dimensional limit equilibrium solution is extended for rectangular plate anchors by introducing the shape factors of Ovesen and Strømann. The solution is compared with a database of 102 pullout model tests of vertical plate anchors in sand assembled from the literature and some limit analysis results. The comparison results suggest that the proposed solution can provide a reliable analytical tool for the ultimate pullout capacity prediction of shallow vertical plate anchors buried in sand. [ABSTRACT FROM AUTHOR]

Soil anchors are among the most widely used reinforcements to stabilize unstable soil mass or stabilize and anchor structures built in onshore and offshore regions. Anchors are generally installed in soil and rocky environments by penetration and embedment methods. These methods are classified into two main groups of grouted and mechanical anchors. In the present study, Expandable Mechanical Plate Anchors (EMPLAs), a new generation of mechanical anchors, are introduced and their bearing capacities are evaluated. EMPLAs can be implemented, locked, and activated in the soil more cheaply and with a lower driving force. Previous studies have validated the efficiency of these anchorages based on the experimental test results. Here, it is tried to evaluate the effect of properties of anchor plates such as their shape and curvature on the locking mechanism, as well as the ultimate bearing capacity of reinforcement and drop rate of locking force under a constant pullout speed rate. Furthermore, the ultimate bearing capacity of the anchors is calculated using two methods of 1) the well-known theories for calculating the tensile bearing capacity of plate anchors in cohesionless soil and 2) numerical modeling using finite element software. The results from both methods showed that the plate curvature intensity had a great impact on the plates opening rate and, consequently, faster locking and activation of the reinforcement at the higher embedment depth. Eventually, the effective zone of the soil at the top of the expandable plates during a 90° rotation of the plates and lockage of the reinforcement was monitored using the Particle Image Velocimetry (PIV) technique. [ABSTRACT FROM AUTHOR]

An innovative plate anchor, increasing its bearing section area during uplift is introduced in this paper. In this experimental study, the influence of the embedment ratio (depth of embedment/anchor width) of the plate anchor and anchor width (120, 150, 180, 250 mm) on the anchor pullout capacity and anchor displacement during an uplift test is investigated. Particle Image Velocimetry (PIV) is used to study soil deformation around the anchor at the maximum pullout load's instant. The pullout loads predicted by prevalent theoretical methods have been compared with obtained experimental values. According to PIV analysis, two failure surfaces are observed and two equations are presented to estimate the ultimate pullout load of the shallow and deep opening plate anchor. It was observed that the pullout capacity ( P u) was significantly influenced by anchor embedment ratio, but the anchor displacement corresponding to the maximum pullout load ( d u) increased slightly as the embedment ratio increased. As the anchor width (B) increased, P u and d u increased, but the breakout factor (dimensionless pullout load) decreased. For shallow anchors, the sand deformation zone lines formed a curve that extended to the soil surface. For deep anchors, the sand deformation zone formed a truncated cone in the soil. [ABSTRACT FROM AUTHOR]

This study describes an analytical solution for determining the ultimate vertical uplift resistance of a group of two and multiple number of close-spaced shallow rectangular anchor plates embedded horizontally in sand. The analysis was performed by using an upper bound theorem of limit analysis with the employment of the kinematically admissible three-dimensional (3D) rigid wedge collapse mechanisms. Results are obtained in terms of dimensionless uplift factors Fγ and Fq due to the components of soil self-weight and surcharge pressure acting on the ground surface for a wide range of parameters. It was found that the magnitude of uplift factors decreases substantially with a decrease in the clear spacing between the anchors, soil friction angle, and embedment ratio, and an increase in the aspect ratio of anchors. Further, it was noticed that when the clear spacing between the anchors is greater than or equal to the certain critical value, the interaction effect of anchors vanishes and the magnitude of uplift factors associated with a group of anchors becomes equal to that of single isolated anchors. The present solutions are found to compare reasonably well with those theoretical, numerical, and experimental results available in the literature. [ABSTRACT FROM AUTHOR]

The present work develops a theoretical model based on a rational mechanical model and the failure mechanism of anchor piles in the seabed, by which the failure mode and pullout capacity of anchor piles under inclined loading can be predicted in the soils with both cohesive and cohesionless properties. Experimental and numerical results are employed to validate the theoretical predictions. Parametric studies are performed to investigate the effects of different parameters on the failure mode and pullout capacity of anchor piles, to demonstrate the applicability and efficiency of the theoretical model and to gain further knowledge of the anchor properties. An analytical method is also proposed to evaluate the optimal position of the attachment point of anchor piles, and confirmed by relevant studies in either cohesive or cohesionless soils. A novel theoretical model is proposed to analyze the failure mode and pullout capacity of anchor piles. The model is applied to inclined loading and to soils with both cohesive and cohesionless properties. Efficiency and applicability of the model are validated through comparative and parametric studies. A simple expression is proposed to predict the optimal position of the attachment point for anchor piles. [ABSTRACT FROM AUTHOR]

The keying mechanism of plate anchors (PLA) embedded into granular sandy soils is investigated in this work using the discrete element method (DEM) modeling to simulate microscale response and to observe the emergent macroscale behavior. Parameters (e.g., padeye eccentricity, loading direction) that influence anchor keying are analyzed in the simulations. The load-displacement response and embedment losses during keying are evaluated and compared to published experimental results from the literature. The keying mechanism of the PLA for different padeye eccentricities and loading directions are investigated. The DEM results are found to have the same trends as published experimental results. The embedment loss has a bilinear response with the padeye eccentricity which is in accordance with the experimental results reported in the literature. Embedment losses increase linearly with increasing loading directions. Microscale observations of mobilized particle friction, particle rotation, contact force network, and steering coefficient during keying are used to provide insights into the keying mechanisms. The potential for particle mobilization is reached more quickly for the larger padeye eccentricities. The particle rotation is the major keying mechanism for all the cases in the simulations. Finally, the granular assembly adjacent to the PLA is steering from horizontal to vertical for all padeye eccentricities. [ABSTRACT FROM AUTHOR]

This paper presents an improved plasticity force-resultant model for anchors deeply embedded in clays, developed from large deformation finite element analyses. The current available force-resultant models for anchors are mainly developed from small strain finite element analysis while experimental approach has not been used due to technical challenges. The advantage of large deformation finite element analysis is that it provides much more data points to fit the yield surface than small strain finite element analysis, in addition to avoiding excess mesh distortion problems. Furthermore, the flow rule or normality can be effectively checked in the large deformation finite element analysis and further used to improve the fitting quality. After validated against retrospective simulations, the better performance of the developed plasticity force-resultant model is demonstrated by comparing with available experimental observations from centrifuge test. [ABSTRACT FROM AUTHOR]

The OMNI-Max anchors are newly developed dynamically installed anchors for deep water mooring systems. After installation, the anchor is keyed to a new orientation and position by tensing the attached mooring chain, which is known as the "keying process". This study conducted 1g model tests to study the trajectories and capacity developments of OMNI-Max anchors in homogeneous and lightly overconsolidated (LOC) clays. A testing arrangement was designed to simulate the anchor keying process with a constant pullout angle at the mudline. A half model anchor which could move against the box glass was used to determine the anchor trajectory in the soil. The effects of padeye offset angle, uplift angle at the mudline, anchor fluke thickness, anchor initial embedment depth, and soil strength on the anchor trajectory and capacity were systematically investigated. Moreover, the critical uplift angle at the padeye and the anchor critical initial embedment depth were discussed. The results indicate that the anchor can dive both in homogeneous and LOC clays under certain conditions. A padeye offset angle of 24–30° is recommended for the OMNI-Max anchor to maintain high capacity and diving trend simultaneously. Besides, the anchor diving trend can be improved with small uplift angles at the mudline and with thick anchor flukes. A critical initial embedment depth of 1.3 times the anchor length is recommended to preclude the anchor from being pulled out. [ABSTRACT FROM AUTHOR]

The uplift capacity of a group of circular plate anchors buried horizontally in sand along a line has been determined. The uplift capacity of an interfering anchor is presented in terms of nondimensional uplift factors, Fγi and Fqi, due to components of soil unit weight and surcharge pressure acting on the ground surface, respectively. Theoretical solutions have been developed by applying the upper bound theorem of limit analysis based on a simple rigid wedge collapse mechanism. In the case of two and infinite number of anchors, closed-form solutions have been developed for computing the factor Fqi, whereas the factor Fγi is determined using a semianalytical approach. As expected, the interference of the anchors leads to a continuous reduction in the uplift resistance with a decrease in the spacing between the anchors, and the uplift resistance decreases with the increasing number of anchors at a given spacing. The results compare reasonably well with the available theoretical and experimental data from the literature. [ABSTRACT FROM AUTHOR]

Numerical solutions have been obtained for the vertical uplift capacity of strip plate anchors embedded adjacent to sloping ground in fully cohesive soil under undrained condition. The analysis was performed using finite element lower bound limit analysis with second-order conic optimization technique. The effect of anchor edge distance from the crest of slope, angle and height of slope, normalized overburden pressure due to soil self-weight, and embedded depth of anchor on the uplift capacity has been examined. A nondimensional uplift factor defined as Fcγ owing to the combined contribution of soil cohesion (cu), and soil unit weight (γ) is used for expressing the uplift capacity. For an anchor buried near to a sloping ground, the ultimate uplift capacity is dependent on either pullout failure of anchor or overall slope failure. The magnitude of Fcγ has been found to increase with an increase in the normalized overburden pressure up to a certain maximum value, beyond which either the behavior of anchor transfers from shallow to deep anchor or overall slope failure occurs. [ABSTRACT FROM AUTHOR]

This paper investigates the static pullout resistance of anchor chains embedded into cohesionless soil. The anchor chains, which are made of steel, were buried into Jumunjin sand whose relative density was set to approximately 60%. The anchor chains were horizontally pulled out through a displacement of 70 mm in laboratory model tests. Three different embedment depths and seven different numbers of chain links were adopted. The pullout resistance of the anchor chains was found to increase with increasing embedment depth and the number of anchor chain links. The measured resistance was significantly higher than the calculated frictional resistance, implying that the passive resistance at the front of the anchor chain significantly contributes to the pullout resistance. The contribution of the passive resistance tends to decrease with increasing number of chain links. [ABSTRACT FROM AUTHOR]

Current floating structures require more reliable and higher anchoring capacities because of their increased size. A suction anchor is one of the most popular anchors for a floating system. In this study, the behavior of a suction anchor installed in cohesionless soil was investigated when the anchor was subjected to mainly a horizontal load. Three-dimensional finite element numerical analyses were carried out using ABAQUS, and three centrifuge tests were performed to calibrate the numerical analyses. A parametric study with different dimensions and loading points for the suction anchor was conducted. The horizontal capacity of the suction anchor was estimated, and the soil reaction distribution was analyzed when the load was applied at the optimal point. Based on the results, an analytical equation for calculating the horizontal capacity of a suction anchor was proposed that can be easily adopted for design. [ABSTRACT FROM PUBLISHER]

This article presents a procedure to calculate the bearing capacity of suction anchors subjected to inclined average and cyclic loads at the optimal load attachment point using the undrained cyclic shear strength of soft clays based on the failure model of anchors proposed by Andersen et al. The constant average shear stress of each failure zone around an anchor is assumed and determined based on the static equilibrium condition for the procedure. The cyclic shear strength of each failure zone is determined based on the average shear stress. The cyclic bearing capacity is finally determined by limiting equilibrium analyses. Thirty-six model tests of suction anchors subjected to inclined average and cyclic loads were conducted, which include vertical and lateral failure modes. Model test results were predicted using the procedure to verify its feasibility. The average relative error between predicted and test results is 1.7%, which shows that the procedure can be used to calculate the cyclic bearing capacity of anchors with optimal loading. Test results also showed that the anchor was still in vertical failure mode under combined average and cyclic loads if an anchor was in vertical failure mode under static loads. The anchor failure would depend on the vertical resistance degradation under cyclic loads if an anchor was in lateral failure mode under static loads. Cyclic bearing capacities associated with the number of load cycles to failure of 1000 were about 75% and 80% of the static bearing capacity for vertical failure anchors and lateral failure anchors, respectively. [ABSTRACT FROM PUBLISHER]

Plate anchors are extensively used in civil engineering constructions as they provide an economical alternative to gravity and other embedded anchors. The rate of loading is one of the important factors that affects the magnitude of soil resistance as well as soil suction force. This article outlines the effect of pullout rate on uplift behavior of plate anchors (70 mm diameter) buried in soft saturated clay by varying the pullout rate from 1.4 mm/min to 21.0 mm/min. The variation of breakout force and suction force with embedment depth and rate of pull are presented. A correlation between the rate of increase of undrained strength of clay and anchor capacity with rate of strain has been established. Finally an empirical equation has been proposed that includes the rate of pull in the estimation of breakout capacity of anchors. [ABSTRACT FROM AUTHOR]