Cipriano Jose de Medeiros

Bio: Cipriano Jose de Medeiros is an academic researcher from Petrobras. The author has contributed to research in topics: Pile & Shear strength (soil). The author has an hindex of 3, co-authored 6 publications receiving 58 citations.

Undrained Load Capacity of Torpedo Anchors Embedded in Cohesive Soils

Abstract: This paper presents a numerical based study on the undrained load capacity of a typical torpedo anchor embedded in a purely cohesive isotropic soil using a three-dimensional nonlinear finite element model. In this model, the soil is simulated with solid elements capable of representing its nonlinear physical behavior and the large deformations involved. The torpedo anchor is also modeled with solid elements, and its geometry is represented in detail. Moreover, the anchor-soil interaction is addressed with contact finite elements that allow relative sliding with friction between the surfaces in contact. A number of analyses are conducted in order to understand the response of this type of anchor when different soil undrained shear strengths, load directions, and number and width of flukes are considered. The results obtained indicate two different failure mechanisms: The first one involves significant plastic deformation before collapse and, consequently, mobilizes a great amount of soil; the second is associated with the development of a limited shear zone near the edge of the anchor and mobilizes a small amount of soil. The total contact area of the anchor seems to be an important parameter in the determination of its load capacity, and, consequently, the increase in the undrained shear strength and the number of flukes and/or their width significantly increases the load capacity of the anchor.

Deep water high capacity anchoring system and method of operation thereof

Abstract: A deep water high capacity anchoring system in which the fixing of an anchor structure under compact layers of ocean soil is reached by jetting fluid in rising directions and, simultaneously in a radial and/or perpendicular direction to the external surfaces of said anchor structure injected from its lower extremity, thus guaranteeing anchoring of large size floating structures, related to the petroleum industry, such as stationary production units and oil drilling platforms.

Pile for anchoring floating structures and process for installing the same

Abstract: A pile for anchoring a floating structure in deep water includes an elongated body provided with a tapered pointed tip at the lower end thereof and a closure disc at the upper end thereof. A plurality of radially and axially extending fins are secured to the pile adjacent the upper end thereof. The elongated body of the pile is filled with material having a high specific gravity distributed in such a manner that the center of gravity of the pile is located well below its center of buoyancy. The process for installing the pile uses the potential energy generated by the free fall of the pile from a vessel in order to ensure that the pile penetrates the ocean floor.

A pile for anchoring floating structures and process for installing it

Abstract: A pile for anchoring floating structures in deep and very deep waters, basically comprises an elongate body (1), provided with a tapered pointed tip (2) at its lower end and a closure disc (3). At its top end it has vertical fins (4) close to the top. The interior of the tubular portion is filled with material of high specific gravity distributed in such a manner that the centre of gravity of the pile is located well below its centre of buoyancy. The process for installing the pile uses the potential energy generated by the free fall of the pile from a vessel, in order to ensure that it penetrates the ocean floor.

Innovative Supports of Risers and Corresponding Installation Procedures

Abstract: Usage of FPSO in shallow water always presents challenges to keep flexible risers’ stresses at the TDP (TouchDown Point) below acceptable values. Depending on the water depth, the catenary configuration can impose excessive high stresses at the TDP and for this reason, configurations like Lazy S, Steep S, Lazy Wave, Steep Wave, Pliant Wave and other complex configurations should be used. Choosing the type of configuration is always dependent on, among others, local environmental conditions, FPSO’s behavior and supports, the water depth, the number of risers, bottom arrangement of them, possibility of line clashes and mainly the cost of the solution. Depending on the number of risers to be supported, construction, installation and keeping good reliability of structural solutions generate considerable increases in the overall investment and maintenance costs. The paper presents two innovative fixed submerged supports of flexible risers, in lazy S configuration, and their installation procedures, that manage to lower construction and installation costs and also decrease inspection tolls due to increased reliability of the structure in comparison to floating buoy solutions.Copyright © 2011 by ASME

Dynamic installation and monotonic pullout of a torpedo anchor in calcareous silt

Abstract: Challenges associated with dynamically installed anchors include prediction of the anchor embedment depth, which dictates the anchor's holding capacity. This is particularly true for calcareous sediments, as very little performance data exist for this anchor type in these soils. This paper reports results from a series of model tests undertaken to provide insight into the behaviour of a torpedo anchor during dynamic installation and monotonic pullout in lightly overconsolidated calcareous silt. The tests were carried out in a beam centrifuge, varying the drop height and consequently the impact velocity, and the consolidation period prior to anchor pullout. The mudline load inclination was also varied to encompass various mooring configurations. The centrifuge model test data were used to calibrate: (a) an analytical dynamic embedment model, based on conventional bearing and frictional resistance factors but with strain-rate-dependent undrained shear strength for the soil; and (b) an analytical quasi-stati...

Experimental Investigation of Installation and Pullout of Dynamically Penetrating Anchors in Clay and Silt

Abstract: This paper reports the results from a series of model tests undertaken to provide insight into the behavior of torpedo anchors during dynamic installation and pullout in lightly overconsolidated kaolin clay and calcareous silt. The tests were carried out in a drum centrifuge at 200g, varying the drop height (hence the impact velocity) and the time delay for consolidation before pullout. The pullout angle at the mudline was also varied to encompass various mooring systems, including catenary (0°), taut leg (45°), and tension leg (∼80°). Two geometries of torpedo anchors were explored, varying the fin and tip geometry. The results demonstrated that the anchor embedment depth increased as the drop height (and hence the impact velocity) increased and the soil undrained shear strength decreased. In stronger silt, the cavity above the installing anchor remained open, whereas in soft clay, it was fully backfilled and replenished. The corresponding anchor embedment depth was also about 0.63 times compared...

Capacity of dynamically installed anchors as assessed through field testing and three-dimensional large-deformation finite element analyses

Abstract: The capacity of dynamically installed anchors in soft normally consolidated clay was examined experimentally through a series of field tests on a 1:20 reduced-scale anchor. The anchors were installed through free fall in water, achieving tip embedment of 1.5–2.6 times the anchor length, before being loaded under undrained conditions at various load inclinations. Vertical anchor capacities were between 2.4 and 4.1 times the anchor dry weight and were satisfactorily predicted using the American Petroleum Institute approach for driven piles. Anchor capacity under inclined loading increased as the load inclination approached horizontal; the field data indicated this increase to be up to 30% for the minimum achievable inclination of about 20° to the horizontal. Corresponding large-deformation finite element analyses showed a similar response, with the maximum capacity occurring at a load inclination between 30° and 45° to the horizontal. The finite element results demonstrate that, for the anchor geometry cons...

Coupled analysis of dynamically penetrating anchors

Abstract: The development of a numerical procedure for the finite element analysis of anchors dynamically penetrating into saturated soils is outlined, highlighting its unique features and capabilities. The mechanical behaviour of saturated porous media is predicted using mixture theory. An algorithm is developed for frictional contact in terms of effective normal stress. The contact formulation is based on a mortar segment-to-segment scheme, which considers the interpolation functions of the contact elements to be of order N, thus overcoming a numerical deficiency of the so-called node-to-segment (NTS) contact algorithm. The nonlinear behaviour of the solid constituent is captured by the Modified Cam Clay soil model. The soil constitutive model is also adapted so as to incorporate the dependence of clay strength on strain rate. An appropriate energy-absorbing boundary is used to eliminate possible wave reflections from the artificial mesh boundaries. To illustrate the use of the proposed computational scheme, simulations of dynamically penetrating anchors are conducted. Results are presented and discussed for the installation phase followed by ‘setup’, i.e., pore pressure dissipation and soil consolidation. The results, in particular, reveal the effects of strain rate on the generation of excess pore pressure, bearing resistance and frictional forces. The setup analyses also illustrate the pattern in which pore pressures are dissipated within the soil domain after installation. Hole closure behind a dynamic projectile is also illustrated by an example.

On the estimation of the falling velocity and drag coefficient of torpedo anchor during acceleration

Abstract: Torpedo anchor installation is a new kind of anchoring system which is much more economical than other conventional anchoring methods. However, there are few studies on the falling velocity and drag coefficient of the torpedo anchors. In this study, seven torpedo anchors with different densities, aspect ratios, scale ratios and fin sizes were utilized to investigate their influence on the falling velocity of the anchor during acceleration. Anchors were released in a water tank and the falling process was recorded using a fast speed video camera. Accordingly, the corresponding drag coefficients against the Reynolds numbers during acceleration were calculated. The Reynolds numbers varied between 4.8×105 and 2.16×106 and the drag coefficients varied between 0.2 and 1.2. The differences between the falling velocities and the drag coefficient for anchors with different shapes, sizes, densities and directional stability were illustrated and the reasons for the differences were explained. The final drag coefficients versus the Reynolds numbers were compared with other representative models found in the literature. The influence of acceleration on the drag coefficient or falling velocity was emphasized. Finally, an Extrapolation Mathematical Model for the motion of the anchor in the fluid was proposed and the results were compared to the experimental data.