Anchor Penetration Research Articles

Dynamic installation of a torpedo anchor in two-layered clays

The behaviour of a torpedo anchor during dynamic installation in two-layered nonhomogeneous clay sediments was investigated through large-deformation finite-element (LDFE) analyses. Parametric analyses were undertaken varying the top layer thickness and strength ratio between two layers. Results show that the location of the demarcation point between the acceleration and deceleration phases of the anchor in the soil relative to the layer interface is the key factor directing the anchor behaviour in layered soils including the final embedment depth. Broadly speaking, the anchor behaviour in soft-over-stiff clay deposits is somewhat similar to that in single layer clay with strength increasing with depth. In stiff-over-soft clay deposits, the anchor penetrates deeper where the anchor deceleration phase (or the demarcation point) falls within the soft layer. Where the demarcation point lies within the top stiff layer, the anchor penetration depth decreases with increasing strength ratio, and the anchor penetration is terminated between the two layers for strength ratios ≥15. For assessing the anchor embedment depth in two-layered fine-grained ocean sediments in the field, an extended total energy–based method, along with a design expression, is proposed.

Toward a quick evaluation of the performance of gravity installed anchors in clay: Penetration and keying

Gravity installed anchors (GIAs) are the most recent generation of anchoring solutions to moor floating facilities for deepwater oil and gas developments. Challenges associated with GIAs include predicting the initial embedment depth and evaluating the keying performance of the anchor. The former involves high soil strain rate due to large anchor penetration velocity, while the later influences the subsequent behavior and pullout capacity of the anchor. With the coupled Eulerian–Lagrangian method, three-dimensional large deformation finite element models are established to investigate the penetration and keying of GIAs in non-homogeneous clay. In the penetration model, a modified Tresca soil model is adopted to allow the effects of soil strain rate and strain softening, and user-defined hydrodynamic drag force and frictional resistance are introduced via concentrated forces. In the keying model, the anchor line effects are incorporated through a chain equation, and the keying, diving and pulling out behaviors of the anchor can all be replicated. Parametric studies are undertaken at first to quantify the effects of various factors on the performance of GIAs, especially on the penetration and keying behaviors. Based on the results of parametric studies, fitted formulae are proposed to give a quick evaluation of the anchor embedment depth after the installation, and the shackle horizontal displacement, shackle embedment loss and anchor inclination at the end of the keying. Comparative studies are also performed to verify the effectiveness of the fitted formulae.

Labral cuff refixation in the hip: rationale and operative technique for preserving the chondrolabral interface for labral repair: a case series.

ABSTRACTArthroscopic labral ‘takedown’ and refixation is utilized to permit adequate visualization and resection of the acetabular rim deformity, in patients with pincer or mixed femoroacetabular impingement. Deficiencies exist in present techniques, which include disruption of vital anatomical support and vascular structures to the labrum and chondrolabral junction, drill or anchor articular penetration risk, bunching, elevation and instability of the labrum. A new operative technique is described which preserves the important chondrolabral interface, accurately restoring the ‘flap seal’ of the acetabular labrum while minimizing vascular disruption and reducing the risk of drill and anchor penetration. A prospective series of 123 consecutive cases of pincer or mixed femoroacetabular impingement, treated with arthroscopic labral cuff refixation and preservation of the chondrolabral interface, is reported; operative technique and 2-year outcomes are presented.

Impact on submarine cables due to ship anchor – soil interaction

AbstractAnchors are one of the main reasons for submarine cable damage. A certain permanent burial depth is necessary if the risk of submarine cable failure due to anchor penetration into the soil is to be reduced. Two factors are important for the burial depth: the penetration depth of the anchor in the first place and the influencing depth of the anchor movement. This means that cables can be damaged either by an anchor penetrating into the subsoil and coming into direct contact with the cable or by an anchor moving above the cable but inducing a pressure load on the cable. To investigate the influence of anchor movement on a submarine cable and to derive the possible damage mechanisms, numerical simulations were conducted using the Coupled Eulerian‐Lagrangian (CEL) method.

Technique for Modeling Installation and Pullout of DIAs on a Beam Centrifuge

Abstract This paper describes a technique for modeling the installation and pullout of a dynamically installed anchor (DIA) using specifically designed equipment on a beam centrifuge. The equipment consists of three subassemblies, an X-Y table, an anchor installation system, and a pullout system. The X-Y table allows the location of anchor installation and pullout direction and pullout angle to be adjusted within a relatively short time without stopping the centrifuge. This permits the pullout angle with respect to vertical and the azimuthal angle of the pullout direction relative to the fins to be adjusted under high-g conditions. Inclined anchor penetration could also be preset by changing the lateral offset of the top of the guide tube. Finally, a very short transition time of several seconds between installation and pullout can be achieved, thereby allowing nearly short-term conditions to be achieved during pullout. The centrifuge model test results show that vertical pullout of non-vertically installed anchors and non-vertical pullout of vertically installed anchors both give a higher holding capacity than vertical pullout of vertically installed anchors. This indicates that the transverse pullout resistance of an anchor may contribute measurably to the anchor capacity and raises the possibility that, when appropriately installed, even higher pullout capacity may be obtainable from inclined pullout of non-vertically installed anchors. The findings also suggest that the ratio of short-term to long-term capacity may differ for different soils, thereby underlining the importance of being able to conduct tests at sufficiently shorter reconsolidation times.

헬리컬 앵커개발 및 적용을 위한 앵커의 회전 관입 토크와 인발저항력과의 상관관계 정립

헬리컬 앵커개발 및 적용을 위한 앵커의 회전 관입 토크와 인발저항력과의 상관관계 정립

A Biomechanical Analysis of Anchor Placement for Bankart Repair: Effect of Portal Placement.

During arthroscopic Bankart repair, penetration of suture anchors through the far cortex can compromise the initial biomechanical characteristics of anchor stability and repair integrity. This study compared the placement of suture anchors through a low anterior-inferior rotator interval portal (AI) vs a trans-subscapularis portal to evaluate the rate of anchor perforation as well as biomechanical strength. Ten matched pairs of cadaveric shoulders were randomized to an AI or a trans-subscapularis portal for placement of suture anchors at the 3 o'clock and 5:30 positions. The following measurements were obtained: (1) distance from the portal to the cephalic vein; (2) presence and length of anchor penetration through the inferior glenoid; and (3) ultimate failure strength of the anchors. The distance from the portal to the cephalic vein was significantly greater with the AI vs the trans-subscapularis portal across all specimens (29.9 vs 11.2 mm, P<.05). The rate of anchor penetration was significantly increased in the AI group vs the trans-subscapularis group at the 5:30 position (60% vs 10%, P=.014) but not at the 3 o'clock position (P=.33). Mean pullout strength of the anchors at the 5:30 position trended higher in the trans-subscapularis group, but the difference was not significant (132.8 vs 112.6 N, P=.18). The cephalic vein is closer to the trans-subscapularis portal than to the AI, but is at a safe distance. Both the rate and the degree of glenoid suture anchor penetration were lower with the trans-subscapularis portal compared with the AI at the 5:30 position. Placing anchors through the trans-subscapularis portal provides a safe alternative method, with improved positioning of the inferiormost anchor compared with the traditional AI.

A prediction method for anchor penetration depth in clays

Anchoring is one of the main causes of subsea pipeline damage, which makes anchor penetration depth one of the most important references for the design of subsea pipeline burial depth. The anchor penetration process is analysed experimentally, numerically and theoretically. First, a series of model tests of dropping anchors are conducted to study the influences of anchor weight, dropping height on the penetration depth. Second, taking the effects of strain and strain rate into account, a finite element method (FEM) model of anchor penetration is set up with Coupled Eulerian–Lagrangian (CEL) method. The soil deformation and effects of strain and strain rate are analysed with the CEL model, and the model is validated against the test results. Then the effects of touch-down velocity and soil properties on penetration depth are analysed with the numerical model. Third, the anchor penetration process is analysed with classical bearing capacity theory. The average bearing coefficient during anchor penetration is back-analysed with experimental and numerical results. And a prediction method for the average bearing coefficient, which takes into account the effect of touch-down velocity, is proposed. Finally, the prediction process for the penetration depth of dropped anchor is proposed. The proposed method is of great significance for predicting anchor penetration depth and subsea pipeline burial depth.

Interactional Properties between Drag Anchor and Installation Line

During penetrating of a drag anchor in seabed soils, complex interaction happens between the anchor and installation line. It is important to clarify the properties of the drag force and drag angle at the shackle of the anchor, which are especially meaningful to the design and theoretical analysis of drag anchors. The interactional properties between the drag anchor and installation line are theoretically and experimentally investigated in the present work. Based on mechanical models for the embedded line and drag anchor, analytical expressions that can predict the drag force at the shackle for both cohesive and noncohesive soils are derived. Theoretical methods are also developed to predict not only the evolution but also the exact value of the drag angle at the shackle during anchor penetration. All the analytical methods are examined by comparing the predicted drag force and drag angle with available experimental data. A detailed parametric analysis is also performed to explore the effects of different parameters on the drag force and drag angle and to determine reasonable values of several key parameters, including the lateral soil pressure factor K, the angle of interface friction δ, and the bearing capacity factor Nq.

Anterior Glenoid Perforation with Suture Anchor Causing Subscapularis Irritation and Pain

Suture anchors for labral repair have been associated with complications including suprascapular notch encroachment and osteolysis. We present a case of suture anchor penetration of the anterior glenoid neck leading to pain secondary to subscapularis muscle irritation in a 14-year-old boy. The patient had labral repair and subsequent anterior shoulder pain which resolved after anchor removal. Chondrolysis of the glenohumeral joint has been described following labral repair with knotless anchors. There have also been cases of injury to the suprascapular nerve following labral repair. However, we are not aware of any reports describing suture anchor penetration of the anterior glenoid neck leading to pain secondary to subscapularis muscle irritation. Labral repair has become a common and routine procedure, but complications can occur. We report a new complication related to osseous penetration of the anterior glenoid neck of the scapula by a suture anchor. We identified the complication using magnetic resonance imaging, an important part in reproducible, noninvasive, and objective assessment of the postoperative shoulder. We also present the technique for anchor removal used to resolve the patient's anterior shoulder pain.

Inferior Anchor Cortical Perforation With Arthroscopic Bankart Repair: A Cadaveric Study

The aims of this study were to evaluate the incidence of anchor penetration of the far cortex of the glenoid neck after arthroscopic Bankart repair and to compare the biomechanical properties of anchors in the 4- and 5:30- to 6-o'clock positions on the glenoid. Twelve (6 matched pairs) fresh-frozen human cadaveric shoulders were used to simulate arthroscopic Bankart repair in the lateral decubitus position. The most inferior anchor (5:30 to 6 o'clock) and that above it (4 o'clock) were inserted via the anteroinferior portal on the glenoid using the standard technique. After both anchor insertions, anchor perforation of the glenoid far cortex was identified. Biomechanical properties were measured to determine cyclic displacement of anchors at 100 and 500 cycles, stiffness, yield load, and ultimate failure strength. All 12 suture anchors (100%) at 5:30 to 6 o'clock penetrated throughout the far cortex, whereas only 4 anchors (33%) at 4 o'clock did so (P = .005). The mean distance the anchor tip traveled into far cortex was significantly longer at 5:30 to 6 o'clock than at 4 o'clock (6.8 ± 1.6 mm v 2.0 ± 1.6 mm, P = .001). In terms of mechanical strength, anchors at 5:30 to 6 o'clock had greater 100- and 500-cycle mean displacements than those at 4 o'clock (3.0 ± 0.5 mm v 2.5 ± 0.3 mm, P = .018 for 100 cycles; 3.5 ± 0.7 mm v 2.8 ± 0.3 mm, P = .018 for 500 cycles), although no differences in ultimate failure strength after cyclic loading were found between 2 positions (133.4 ± 40.3 and 133.7 ± 29.2 N, respectively; P = .985). For arthroscopic Bankart repair, insertion of the most inferior anchor via the anteroinferior portal with standard technique, in the lateral decubitus position, carries a high risk of perforating the inferior far cortex of the glenoid (100% in our study). This may result in mechanical weakness of the most inferior repair specifically in the early postoperative period. Perforation of the glenoid far cortex by the most inferior anchor and its mechanical weakness should be taken into consideration. Further study is needed to improve surgical technique to place the most inferior anchor in an optimal position by arthroscopy.

Discussions about Scaling Rules of Suction Anchor Model Tests

Based on the equation analysis method and theorem dimensional analysis, the scaling rules between field tests and mode tests for embedded suction anchors have been investigated. Some critical parameters affecting the characteristics of anchor penetration and capacity are studied in detail. It is illustrated that although adopting non-normal scale because of using prototype of soil and water in model tests, the model tests could reflect the qualitative nature in field tests through adjusting some critical scale factors.

A Radiographic Investigation to Determine the Safety of Suture Anchor Systems for Pediatric Modified Broström Ankle Ligament Reconstruction

Background The modified Broström ligament reconstruction using anchor sutures has been performed in adults with clinical success; however, the safety parameters for the use of suture anchors in adolescent lateral ankle ligament reconstruction have not been established. Purpose To perform a radiographic analysis comparing the depth of penetration of suture anchors in adult ankle ligament reconstruction with the average distance of the physis from the tip of the fibula in adolescents. Study Design Cross-sectional study, Level of evidence, 4. Methods Forty postoperative ankle radiographs of adult patients who had a modified Broström procedure were compared with 40 normal adolescent ankle radiographs. In the adult group, the distance of the suture anchor penetration from the distal tip of the fibula was measured; in the adolescent group, the distance of the physis from the distal tip of the fibula was measured. Results The mean depth of the suture anchors was 17 mm (range, 14-21 mm) from the tip of the fibula in the adult group, and the mean distance of the growth plate was 23 mm (range, 18-29 mm) in the adolescent group. Eight radiographs from the adolescent group (20%) had a physis measurement of <22 mm on the anteroposterior or mortise view. Conclusions Using careful preoperative planning and intraoperative technique, it is possible to safely perform lateral ankle ligament repair in the skeletally immature patient using suture anchors.

Using the anchoring device of a comet lander to determine surface mechanical properties

Owing to the low surface gravity of the Rosetta target comet 46P/Wirtanen, a means of anchoring the Rosetta Lander to the cometary surface will be necessary. This task can be accomplished by firing an anchor into the cometary soil immediately after touchdown to prevent a rebound of the spacecraft from the surface or subsequent ejection by other forces, and to allow for mechanical activities (drilling, etc.) at the landing site. The rationale for anchoring is examined, based on estimates of the main forces likely to act on the spacecraft after landing. We report on the development of an anchoring device using a pyrotechnic gas generator as a power source and an instrumented anchor. In addition to the anchoring function, which is the primary purpose of this system, the integration of acceleration and temperature sensors into the tip offers the possibility to determine some important material properties of the cometary surface layer. The accelerometer is designed to measure the deceleration history of the projectile and is thus expected to give information on how the material properties (in particular strength) change within the penetrated layer(s), while the temperature sensor will measure temperature variations at the depth at which the anchor finally comes to rest. As the mechanical properties of the material are not known, it is difficult to predict the final depth of the anchor with any great certainty, but it may well be greater than that reached by any other of the lander's instruments. The instrumented anchor will be part of the MUPUS experiment, selected to form part of the Rosetta Lander payload. We report on results of laboratory simulations of anchor penetration performed at the Institut für Weltraumforschung, Graz, and compare these with models of projectile penetration. The value of the results expected from the penetrometry experiment in the context of an improved understanding of cometary processes is discussed.

Model experiments for propellant embedded rock anchors

Propellant embedded anchors can be used to secure offshore platforms by rapidly anchoring them in seafloor rock. Field tests conducted by the U.S. Navy showed inconsistent results. A more promising approach seems to be modelling of anchor penetration and pullout resistance in jointed rock based on first principles. In this paper, physical model tests are described with which the physical phenomena are investigated and which will serve as a basis for predictive analytical models. The laboratory experiments, conducted with fasteners to model the anchors and with jointed and intact rock models made from gypsum, showed that basic intact material properties, joint configuration and individual joint properties influence penetration and pullout resistance. If the behavior is brittle, penetration is accompanied by cracking, otherwise ductile continuum deformation occurs. Jointing affects cracking in that closer joint spacing restricts cracking to fewer “joint bounded plates” but increases the number of cracks in the individual plate. The increased cracking intensity leads to a reduced pullout resistance. For purposes of analytical modelling, one can therefore, in a first step, build upon established relations between intact meterial, joint geometry and individual joint characteristics.