Anchor Penetration Research Articles

Numerical assessment of ship anchor penetration depth in Baltic Sea Sand: Implications for subsea cable burial

As renewable energy demand increases, protecting subsea cables from ship anchor damage has become essential. This research comprises numerical simulations of the anchor penetration process in Baltic Sea sand (for an AC-14, a Hall and a Spek anchor). We apply a coupled Eulerian–Lagrangian (CEL) framework and a hypoplasticity constitutive model to analyze the influence of different anchor characteristics on penetration depth and seabed stress distributions. We conducted investigations under high velocities (v≥1m/s) with focus on inertial effects only. Furthermore, this study introduces stress circles to visualize a simplified anchor-induced spatial stress distribution in the seabed. Findings show that heavier anchors and slower drag velocities generally result in deeper anchor penetrations. Fluke geometry significantly affects penetration depth, with pointed designs penetrating more deeply. The observed trends align with previous results from centrifuge tests and numerical modeling of ship anchors. This research improves understanding of soil–structure interaction in maritime environments, offering insights for the protection of subsea installations in the Baltic Sea and similar regions.

Reliability-based evaluation of ultimate embedment depths of torpedo anchors in spatially variable clay

In this study, a large deformation random finite element (LDRFE) method was used to investigate the dynamic penetration of anchor piles in spatially variable clay. Validation of the rationality of the proposed methodology using data from published studies. The randomness of the undrained shear strength of the soil in the system is considered by three-dimensional random fields to investigate the anchor penetration mechanism and quantitatively assess the ultimate embedment depths (Hran ) of the anchor in spatially variable clay. The strain softening and strain rate effects of the soft clayey soil were considered. The findings indicate that the variability in soil strength significantly affects the flow pattern and failure mechanism of the soil, consequently influencing the Hran of the anchor. Furthermore, according to the computed Hran results, a coefficient of variation of soil shear strength φ can be used to connect the deterministic (Hdet ) and random analysis results. This correlation may facilitate further development of reliability-based designs.

Installation Disturbance of Helical Anchor in Dense Sand and the Effect on Uplift Capacity Based on Discrete Element Method

Helical anchors have been extensively employed as foundation systems for carrying tension loads due to their installation efficiency and large uplift capacity. However, the installation influences of helical anchors are still not well understood, especially for multi-helical anchors. The matrix discrete element method was used to model the process of helical anchor penetration and pull-out in dense sand to investigate the effects of the anchor geometry and advancement ratio (AR, the relative vertical movement per rotation) on soil disturbance, the particle flow mechanism, and the uplift capacity. For shallow helical anchors, the overall disturbance zone is the shape of an inverted cone after installation, while for deep helical anchors, it is funnel-shaped. The advancement ratio has significant effects on the soil particle movement and uplift capacity of helical anchors. The soil particle flow mechanism around helical plates has been identified for single-helix anchors at various advancement ratios, and for double-helix anchors, the influence of the top plate on particle movement during installation was investigated. The uplift capacities of both single- and double-helix anchors increase with the decrease in the AR (AR = 0.5~1), and the influence decreases with the anchor embedment ratio. The efficiency of double-helix anchors induced by installation is close to 1 at pitch-matched installation (AR = 1), indicating that the impact of the top plate during installation is minimal in this case.

Formulation of Anchor and Chain Specifications for Establishing Subsea Cable Burial Depth

The penetration of ship anchor, which is a very important factor considered in the design stage of subsea cable burial, is highly dependent on the geometrical specifications and shapes of the anchor and chain. In order to facilitate predicting the anchor penetration depth by an arbitrary ship, formulations of the correlation between the ship mass and the existing anchor and chain specifications were attempted. In particular, for small ships with an equipment number of 40 (corresponding to DWT 90) or less, which were not covered by the existing classification data, a method for estimating the anchor mass, chain diameter, and mass per unit length was proposed.

Numerical Analysis for Estimating Penetration Depth by Ship-dragged Fluke Anchor

Anchor penetration by ship anchoring is emerging as a major risk factor for submarine cable. A numerical analysis method was established to predict the anchor penetration depth by ship-dragged fluke anchor in relation to setting the optimal burial depth of submarine cable. The soil resisting forces (bearing force, friction force) generated during the anchor penetration process were calculated for each of the fluke, shank and mooring chain of the anchor. The results of the numerical analysis were compared with the existing chart values of Vryhof (2015). It was found that it is desirable to use the force coefficients of strip foundation for the fluke and shank, and the force coefficients of a single vertical pile for mooring chain. The numerical analysis well reproduced the penetration trajectory in which the inclination angle of the lower surface of fluke gradually converged to zero.

Dynamic installation of torpedo anchors in slightly overconsolidated clay-overlaying-sand deposit

Torpedo anchor installation involves uncertain design and construction parameters, especially in layered soil deposits. Large deformation finite element and coupled Eulerian–Lagrangian (LDFE/CEL) analyses are performed in this study to elucidate the dynamic installation of torpedo anchors in an over consolidated clay-overlaying-sand deposit. The parametric analysis is conducted after model verification to explore the effect of upper clay layer thickness, anchor impact velocity, anchor submerged weight, soil properties and anchor geometric dimensions. The soil failure patterns and dynamic installation behaviour in the clay-overlaying-sand soil deposit are found to differ substantially from those in single-layer clay and sand deposits, which exhibit a squeezing flow pattern at the clay-sand soil layer interface. As the demarcation of the two velocity phases during the anchor penetration process (acceleration and deceleration phases) falls below the interface of two soil layers, the contribution of the internal friction angle of sand to the anchor final penetration depth exceeds that of the clay undrained shear strength. Based on intensive modelling data, an empirical method for predicting the anchor penetration depth in single and layered soil deposits is derived for engineering applications.

Comparison of suture anchor penetration rate between navigation-assisted and traditional shoulder arthroscopic capsulolabral repair.

Proper placement of suture anchors is an important step in Bankart repair as improper placement can lead to failure. Concern surrounding suture anchor placement inspired the use navigation systems in shoulder arthroscopy. We aimed to demonstrate the technological advantage of using the O-arm (Medtronic Navigation, Denver, CO, USA) image guidance system to provide real-time images during portal and anchor placements in shoulder arthroscopy. Consecutive patients (from July to October 2014) who were admitted for arthroscopic capsulolabral repair surgeries were included. Ten patients were randomly enrolled in the navigation group and 10 in the traditional group. The glenoid was divided into four zones, and the penetration rates in each zone were compared between the two groups. In zone III, the most inferior region of the glenoid, the penetration rate was 40.9% in the traditional group and 15.7% in the navigation group (P = 0.077), demonstrating a trend toward improved accuracy of anchor placement with the aid of the navigation system; however, this was not statistically significant. Average surgical time in the navigation and traditional groups was 177.6±40.2 and 117.7±17.6 mins, respectively. American Shoulder and Elbow Surgeons Shoulder Scores showed no difference before and 6 months after surgery. This pilot study showed a trend toward decreased penetration rate in O-arm-navigated capsulolabral repair surgeries and decreased risks of implant misplacement; however, possibly due to the small sample size, the difference was not statistically significant. Further large-scale studies are needed to confirm the possible benefit of the navigation system. Even with the use of navigation systems, there were still some penetrations in zone III of the glenoid. This penetration may be attributed to the micro-motion of the acromioclavicular joint. Although the navigation group showed a significant increase in surgical time, with improvements in instrument design, O-arm-navigated arthroscopy will gain popularity in clinical practice.

Study on Buried Depth Protection Index of Submarine Cable Based on Physical and Numerical Modeling

The buried depth of submarine cables is very important to avoid damage on the cable from dropping and dragging anchors. This study focused on the actual engineering needs of submarine power cable protection and laying construction. In order to investigate the buried depth protection index of submarine cable, physical model tests, theory analysis, and numerical simulations were conducted in this study. The effects of the bottoming velocity, dropping energy, and anchor mass on the anchor penetration depth were analyzed and investigated. The analytical model based on the impact and drag mechanism is presented to analyze the forces and energy on the anchor. The accuracy and reliable of the model test results are verified by the theory analysis and numerical simulation, indicating that the buried depth protection index of the submarine cable in the research area is recommended to be 3 m. The research results can provide guidance for operation of the submarine cable laying machine and submarine cable protection.

Anchor penetration depth in sandy soils and its implications for cable burial

Modern society is dependent on offshore cables and consequently cable faults lead to major disruption and economic loss. The most effective way to protect offshore cables from anchor damage is to bury them in the seabed, but current guidance is ambiguous. This paper attempts to produce more rational design guidance for anchor penetration in sand based on centrifuge modelling, allowing suitable burial depths for cables to be calculated based on the more useful metrics of anchor or ship size.A miniature anchor was dragged through sand of different densities within a centrifuge with maximum anchor penetration being measured. The most significant factor that influences anchor penetration depth is the size of the anchor, investigated by completing centrifuge tests at different g-levels. A linear relationship was recorded between anchor size and penetration depth which was used to develop new guidelines for cable burial. The new chart is clear and easy to use, with the cable burial depths given in relation to anchor size, anchor mass and ship mass. Use of this chart will enable the safe and economic burial of cables, and lead to a decrease in the impact of anchor damage to offshore cables.

Numerical Simulation Analysis of the Characteristics of Torpedo Anchor Penetration in Cohesive Soil

Yue, L.; Wang, Q.; Wang, W.; Wang, Y., and Lv, J., 2020. Numerical simulation analysis of the characteristics of torpedo anchor penetration in cohesive soil. In: Wan, Z. (ed.), Coordinated Sustainable Development in Coastal Areas: Environment and Economy. Journal of Coastal Research, Special Issue No. 109, pp. 139–144. Coconut Creek (Florida), ISSN 0749-0208.Invented by Petrobras in 1996, the torpedo anchor has been successfully applied in Floating Production Storage and Offloading (FPSO) in the Gulf of Mexico (Medeiros, 2002). With a torpedo-like hydrodynamic shape, the torpedo anchor obtains the kinetic energy required for penetration by free-falling through the water. It then uses that energy to penetrate into the seabed, thereby completing its installation. This paper discusses the large deformation finite element method and the CEL method, which are used to calculate the torpedo anchor penetration in a cohesive-soil seabed. The characteristics of the soil and the anchor at different moments during the torpedo anchor penetration are analyzed based on simulation results.

Visualizing the effect of Fin length on torpedo anchor penetration and pullout using a transparent soil

The effect of torpedo shape on its penetration depth and pull out capacity is explored using laboratory-scale experiments. The study offers a number of useful practical implications for the design of full-scale torpedo anchors. Results demonstrate that the resistance to penetration and extraction of torpedo anchors is strongly affected by their fin design. A transparent soil surrogate made of Magnesium Lithium Phyllosilicate (MLPS), was employed to simulate soft marine clay. Three torpedo models having a length to diameter (L/D) ratio of eight and a similar weight (W), but different fin length to diameter ratios (LF/D) of zero (no fins), 2.6, and 5.2, were penetrated, vertically, at an impact velocity of 4.5 m/s. It was found that fin length correlated negatively with penetration depth (P) and positively with the maximum resistance to extraction. However, the maximum extraction resistance, normalized by weight (W), increased from 2.3 for the case of no fins to 3.1 for short fins and to 3.6 for long fins. Transparent soils enabled measurement of in situ displacements within the target during penetration and pullout and correlating them to the torpedo behavior. Soil displacement increases with the increase of penetration depth till full embedment, after that displacements remain constant.

Evaluation of Anchor Penetration Depth based on Numerical Analysis for Burial Protection Method of Submarine Cables

Submarine cables are installed and operated for the stable power supply of island regions, and feature protective measures to counter marine hazard factors. With regard to the protection techniques to prevent damage to submarine cables, the method of digging and embedding the submarine ground is applied the most. However, since there are no design criteria and techniques for such protection facilities, the burial depth of the submarine ground has been calculated only qualitatively and empirically after an ocean survey is conducted. Such an imperfect method has led to assorted damages to submarine cables. Therefore, in this study, to ensure the safety of submarine cables from marine hazard factors, the three-dimensional dynamic interaction analysis model was established for the ship anchor and ground, and the penetration depth of this anchor was calculated through numerical analysis for the burial protection method. These results were compared and evaluated with the results of the full scale test for anchoring and dragging anchor. As a result, the error rate(average) of the anchor penetration depth through the numerical analysis and test was 12.2% in the ground conditions of sand, clay and multi(clay/sand) layers. This error rate was analyzed to be caused by various uncertainties in the test, such as the dynamic impact of the anchor and ground conditions, and the numerical analysis was evaluated to ensure sufficient reliability. The results of this study are expected to be useful in the burial depth calculation of the burial protection method to ensure the safety of submarine cables.

Research on the characteristics and physical model test method of penetration depth for ship emergency anchoring

Based on the whole process theory, the characteristics of penetration depth for ship emergency anchoring are summarized. Combined with the actual project, the physical model test was carried out, and the scale ratio was set for the soil and anchor. Different working conditions are designed for water flow, vertical height and horizontal velocity Angle, and the model test of anchor penetration depth was carried out. The experimental results show that whether there is water flow or not and the variation of water flow conditions have certain effects on the penetration depth of anchor; when the anchor only has vertical velocity, the faster the anchor hits the bottom, the deeper the anchor penetrates into the soil; when the anchors have horizontal velocity synchronously, the penetration depth of the anchors increases slightly. Compared with the traditional model, the results obtained by this method are closer to reality and provide ideas and references for penetration depth for ship emergency anchoring.

Buried Depth of a Submarine Pipeline Based on Anchor Penetration

Anchor penetration is an important issue involved in the study of submarine pipeline damage accidents. To explore the penetration of a ship’s anchor under certain conditions, this study investigated the motion and force of an anchor and formulated a calculation method for the bottoming speed of an anchor. Meanwhile, the depth of anchor penetration was calculated under different conditions according to bottoming speed through programming. Finally, the reliability of the calculation method for the penetration depth was verified by comparing the actual measurement and the numerical simulation. On the basis of the findings, the calculation results were further analyzed, and conclusions were derived regarding the relationship between anchor mass, the horizontal projected area of the anchor, the anchor height on the water surface, and water depth. The conclusions provide suggestions for the application of anchor penetration in terms of seabed depth with certain reference values.

Estimation of Submarine Cable Burial Depth using CBRA Model

Submarine cable plays an important role in land-island power supply, and domestic and overseas communication. However, damages to the submarine cable have been caused by various dangerous factors such as ship anchors and trawlers. Even though the annual cost for recovering submarine cables is enormous, there is no definite method for protecting submarine cables. The present study investigates the applicability of Cable Burial Risk Assessment (CBRA) model to the estimation of the burial depth of submarine cables. This technique employs a statistical approach to the marine environment of the target area and the navigation data of nearby passing ships. Two computer programs have been developed to facilitate the calculations of anchor penetration depths in clay and sand, respectively. An example application of CBRA model was demonstrated here taking a tentative cable route to Haenam - Jeju sea area. The cable burial depth was calculated to vary from a minimum of 0.6m to a maximum of 0.74m for a 2500 year return period and a minimum of 0.6m to a maximum of 1.40m for a 25,000 year return period. This study also determined the target ship weight in the CBRA model through the statistical expectation. The expected cable burial depth appeared from a minimum of 0.6m to a maximum of 1.26m.

Numerical Prediction of the Trajectory of Fluke Anchors in Sand

The damage to submarine cable caused by the vessel anchoring has been constantly occurred, and the penetration depth of the anchor during vessel anchoring is a very important factor in the stability evaluation of the submarine cable. Clay seabed has undergone many studies in relation to anchor penetration. However the study of sand seabed is still insufficient. Therefore, this study presents a numerical model that can calculate the trajectory of the vessel anchor, the maximum penetration depth and the ultimate holding capacity in sand seabed, considering the static equilibrium relation of the force and moment acting on the anchor and the kinematic behavior of the lower surface of fluke. This study also developed a program (K-Sand) that can interpret the model with EXCEL VBA. Then the program (K-Sand) was verified with chart data on the Vryhof manual. The anchors of the Stevin Mk series were applied to the model verification, and the fluke shape of the anchors were converted to the square of the same area. As a result of the verification, the calculated values for the maximum penetration depth and the ultimate holding capacity data are within 10% of the chart data.

Discrete numerical simulations of torpedo anchor installation in granular soils

Torpedo anchors are a viable approach for mooring marine hydrokinetic (MHK) energy devices to the seafloor. These anchors can serve to maintain station and to provide the reaction force for an MHK device. The ability of the anchor to perform these duties is a strong function of its penetration depth during installation. This is a large-strain problem not amenable to typical continuum numerical approaches. In the current work, we propose that the discrete element method (DEM) is a more appropriate tool to investigate the shallow penetration of torpedo anchors in sands. The effects of anchor mass, impact velocity, and soil interparticle friction are considered in the DEM simulations. The relative maximum penetration depths for different penetration conditions are quantified and presented. Granular material response at the microscale during penetration are used to provide insight into system response. Energy dissipation in the assembly by both friction and collision at the particle scale are considered. Results show that anchor penetration increases approximately linearly with an increase in impact velocity or anchor weight. Penetration decreases with an increase in interparticle friction (i.e., soil strength). Observations of microscale behaviors and energy calculations are used to provide insight into overall system response.

An innovative booster for dynamic installation of OMNI-Max anchors in clay: Physical modelling

An innovative booster concept is proposed to increase both the kinetic and potential energies and hence to increase the penetration depth of the OMNI-Max anchor within the clayey soil with high strength gradient. This paper carried out 1g model tests to investigate the working efficiency of the booster on the anchor penetration depth both in normally consolidated (NC) and lightly over-consolidated (LOC) soils. The similarity relationships of the anchor dynamic penetration within the soil were first deduced, and then a series of dynamic penetration tests were performed to investigate the parameters that influence the anchor penetration depth. The parameters include the soil strength characterisation, impact velocity, booster weight, inclined impacting angle, and water drag and entrainment effects. The anchor dynamic penetration process within the soil was measured by a micro-electromechanical systems (MEMS) accelerometer, through which the soil strain-rate effect and the hydrodynamic aspects including the water drag force and potential water entrainment along the anchor-soil interface were analysed. Finally, energy-based and force-based prediction models were put forward to estimate the penetration depths of OMNI-Max anchors and hybrid anchors (i.e. an OMNI-Max anchor with a booster).

考虑浅埋破坏的拖曳锚在黏土中安装运动特性分析

The drag anchor is widely used in offshore engineering as a foundation for the mooring system due to high capacity and low cost. The prediction of kinematic behavior and trajectory is still challenging due to the complex interaction of the anchor fluke with soil. The existing plastic yield envelope method is generally used for the kinematic analysis, where the deep anchor failure is assumed to occur during the whole dragging process. In reality, the penetration is a process of anchor fluke being dragged into seabed soil continuously from shallow to deep depths. Obviously, the existing yield envelope method could not capture the effect of shallow anchor failure, which may lead to inaccurate prediction of the anchor trajectory. Finite element analyses were conducted firstly to obtain the influences of the anchor embedment depth and angle of the fluke on the drag anchor behaviors under unidirectional and combined loadings. The yield envelope for the shallow anchor failure was determined accordingly, with which the shallow failure effect can be taken into account for the yield envelop method. The effects of the fluke angle, the bearing capacity factor and the shallow zone size were investigated. The predicted trajectories with and without the shallow failure effect were compared. It is shown that the fluke angle and the shallow failure zone size influence significantly the kinematic behaviors and the trajectory of the drag anchor. The consideration of shallow failure results in a shallower predicted anchor embedment depth and a smaller anchor line force before the anchor penetration depth stabilizes, but hardly changes the ultimate embedment depth.

Design of Rock-berm by Anchor Dragging Simulation using CEL Method

In this study, an anchor dragging simulation was performed using the CEL method to design a rock-berm, which is a protection method for submarine cables. In order to simulate an anchor drag, preliminary simulations were first performed to determine the initial anchor penetration depth, anchor drag velocity, drag angle, and distance between the anchor and rock-berm. Based on the preceding simulation results, a safe rock-berm design for protecting the submarine cables was simulated to calculate the anchor penetration depth by the anchor dragging. As a result, the penetration depth of the anchor was found to be shallower in a hard seabed, and the penetration depth was deeper in a soft seabed. , the height of the rock-berm was determined according to the physical properties of the seabed.