Offshore Piling Research Articles

Integrated Multi-Sensor Real Time Pile Positioning Model and Its Application for Sea Piling

The traditional pile positioning method for offshore piling uses the intersection of lines of sight with two or three theodolites. This method has certain limits, including using post-mission pile positioning, being time-consuming and lacking position accuracy. A novel pile positioning model using four kinds of sensors (GNSS—Global Navigation Satellite System receivers, tiltmeters, laser rangefinders and calibrated CCD cameras) for sea piling was developed. Firstly, with Real Time Kinematics (RTK) GNSS and tiltmeter data, the piling ship’s position and attitude was achieved in real time, and then the coordinates of the pile center in the Ship Fixed Coordinate System (SFCS) were calculated by a laser rangefinder and a CCD camera data. Finally, using the coordinate transformation, the coordinates of the pile center construction were figured out and used to guide the pile movement to the right place in real time. Because of the poor RTK GNSS vertical accuracy (normally 2–3 cm) and complex piling ship structure, it is difficult to get the accurate penetration value per hammering, which is a very important parameter for structural engineers. A Scale Invariant Feature Transform (SIFT) algorithm was created to get the pixel difference between the two pile images captured before and after one hammering, respectively, which was then used to calculate the penetration. A case study on the piling ship named “YangShanHao” with the sensors and algorithms was also described and discussed in the paper. The results showed the high accuracy of the proposed position model and the pile sinking distance of the pixel, thanks to the SIFT algorithm.

An appraisal of end conditions in advanced monotonic and cyclic triaxial testing on a range of geomaterials

Compressing samples between rigid platens, as in triaxial testing, induce non-uniform specimen stress, strain and pore water distributions. Although well recognised historically, the effects of such platen restraints are often disregarded or overlooked when performing or interpreting monotonic and cyclic experiments. This paper presents an updated appraisal of end conditions based on laboratory experiments run on sand, glacial till, intact and puttified chalk as part of offshore piling research projects. Monotonic and cyclic triaxial tests are reported that incorporated local strain and pore pressure sensors and a range of platen configurations. New insights are reported regarding the small-to-large behaviour and undrained cyclic pore water pressure measurement.

Effective Offshore Piling Noise Mitigation in Deep Waters

Effective Offshore Piling Noise Mitigation in Deep Waters

High-resolution spectral-element computation of underwater noises due to offshore piling

Offshore piling has been effective in building foundations of offshore structures, such as wind turbines, bridges, and oil rigs. Despite such merits, underwater noise due to offshore piling is considered to be its critical setback. Pile driving creates a high-level underwater sound that harms marine ecosystems. There have been studies that successfully predicted these noises by using numerical methods, for example, Finite Element Method (FEM). However, there has been no FEM study that considers anti-symmetric irregular domains and complex bathymetry to compute underwater noises in the high-frequency range (>1000 Hz) due to expensive computational costs of FEM. To bridge the gap, this work attempts to explore a novel, powerful simulation tool to efficiently obtain offshore piling noises in complex settings and in the high-frequency range. We adopted and modified an open-source large-scale parallel Spectral Element Method (SEM) wave simulator, SPECFEM3D. SEM is known to be much more efficient than FEM for wave propagation analysis problem of a very large number of elements and time steps without compromising accuracy. Our computational method can be used for prediction of offshore piling underwater noise and investigating novel piling methods, such as optimized shapes of piles or air bubbles curtains to mitigate underwater noise.

Efficient application of encapsulated bubbles and foam elements to mitigate offshore piling noise

The very high noise levels of offshore piling noise during the installation of offshore wind converters are dangerous to marine life like harbor porpoises and fishes. Encapsulated bubbles and foam elements are successfully used to reduce the very high noise levels. There are different physical effects such as impedance mismatch, resonance and scattering effects and material damping effects that are responsible to the measured noise reduction between about 10 dB (SEL) and 23 dB (SEL). The radiation of underwater noise from the pile surface, the propagation and the reflections of the radiated waves are investigated together with the influence of encapsulated bubbles and foam elements in the near field of the pile. Only a very small part of the impact energy is radiated directly from the pile into the surrounding water. Most of the hammer energy is driven into the ground. A small part from this is radiated indirectly from the ground into the water. The efficiency of encapsulated bubbles and foam elements in underwater noise mitigation is investigated by theoretical studies, laboratory measurements, and by offshore measurements with different elements and combinations.

Modified Case Method for Piles with Section Step Changes

Applied during pile driving, the Case Method offers an immediate estimate of the static resistance to driving (SRD) after each hammer blow. It has been used in its original form both in the onshore and offshore piling industry for more than 40 years to provide an indication of the pile static capacity. The Case Method requires measurements of force and velocity near the pile head as the hammer strikes the pile and produces an analytical estimate of the SRD, using a number of assumptions. One of them requires the pile to be of constant impedance (or cross section) along its length. However, for reason of economy, driven piles are often composed of several sections of different cross sections. The Case Method provides in that case an inaccurate estimate of the SRD. This article presents an improved version of the original Case Method which takes into account possible variations of impedance along the pile. A numerical validation shows that for piles displaying impedance changes, the modified Case Method presented herein provides an estimate closer to the actual SRD than the original Case Method. That conclusion is further validated by applying the modified Method to pile driving records and comparing its results to SRD estimates obtained through more reliable modelling.

Testing mortality of fish larvae due to simulated offshore piling noise.

Driven by the concern that impulsive noise produced by offshore pile driving may lead to mortality of fish larvae, a device was developed for testing the sensitivity of small fish and fish larvae to sound exposure. The device consists of a rigid‐walled cylindrical chamber (110‐mm diameter, 160‐mm height), driven by an electrodynamical sound projector. Samples of up to 100 larvae can be exposed simultaneously to a homogeneously distributed sound pressure and particle velocity field, at a controllable static pressure up to 3 bars. Two configurations are available with either a dominant sound pressure or a dominant particle velocity exposure. Recorded piling noise can be reproduced in a controlled way, in the frequency range between 50 Hz and 1 kHz, at zero to peak pressure up to 40 kPa and single pulse sound exposure levels up to 187 dB re 1 μPa2 s, or peak particle velocity up to 2.2 cm/s and integrated square particle velocity level 124 dB re 1 (nm/s)2 s. Tests are carried out in which sole (Solea solea) larvae at different stages of development were exposed to various levels and durations of piling noise.

Methodology for environmental impact assessment of underwater noise on marine mammals

The oil and gas industry uses some exploration and production technologies that produce high levels of underwater sound, such as seismic surveys, underwater blasting for demolition and construction, and offshore piling. These underwater noise sources have the potential to impact marine species, which are usually reliant on sound instead of light as their primary sense for communication and sensing their environment. Regulatory interest in minimising the impacts of underwater noise on marine fauna is increasing. This paper presents a methodology for assessing these environmental impacts, with particular focus on cetaceans (whales and dolphins) and pinnipeds (seals and sea lions), although it can easily be adapted to other marine mammal species and fishes. It requires input from a variety of fields, such as: underwater acoustics for sound propagation modelling and source noise characterisation; marine bio-acoustics for determining the effects of sound on marine species’ hearing and communication; and marine ecology for identifying the marine species that may be affected and assessing the biological importance of noise-affected marine areas. These inputs are used in a risk assessment to assess the likely impacts of underwater noise on marine species, which is a collaborative effort by specialists in the fields of underwater acoustics, marine bio-acoustics and marine ecology.

Experimental Investigations of Response of Suction Caissons to Transient Vertical Loading

Suction caissons are a relatively new design being considered for use as foundations in a wide variety of offshore applications. They are unusual in that, in contrast with the development of offshore piling, there is no onshore experience that can be used as the basis for the development of designs. It is therefore essential to identify key behavioral patterns and mechanisms that govern capacity under a wide variety of loading regimes, particularly those derived from the cyclic wave loading. The object here is to establish a broad framework of response. More detailed work specific to a site or project would be required for detailed design. This paper describes experimental investigations into the vertical loading response of a suction caisson foundation. The experiments are carried out on the laboratory floor using a sophisticated three-degree-of-freedom loading rig. The caissons are embedded in sand saturated with viscous silicon oil so that modeled drainage times are representative of typical offshore conditions. The experiments involve cyclic loading about different mean loads, including cycling into tension and monotonic loading at different rates. The relationship between the cyclic loading and monotonic loading is explored. One of the key conclusions from the results is that serviceability requirements will dictate design rather than capacity. Perhaps surprisingly, for the experiments undertaken, the rate of loading had little effect on the response.

Applications of stress-wave theory to piles, quality assurance on land and offshore piling

Applications of stress-wave theory to piles, quality assurance on land and offshore piling

Applications of stress-wave theory to piles, quality assurance on land and offshore piling

Applications of stress-wave theory to piles, quality assurance on land and offshore piling

Self-Edjing Piling Platform Cantilevered from Damaged Quay Walls for Waterfront Piling

This paper is to introduce a cantilever-type working platform (CWP) which moves sideways along existing qauy walls, so that offshore piling work can be carried out onshore instead of offshore, which increases work efficency and avoids traffic congestion in waterfront. CWP was employed for the restoration of the quay walls located at Pon-Island in Kobe, damaged during the Hyogoken-Nanbu earthquake in 1995, for the purpose of speedy restoration of damaged quay walls with the adjacent quay in oparation. As a result, the restoration work had been completed in a timely manner and the restored quay received the first ship on July 1, 1996.

Numerical methods in offshore piling

Numerical methods in offshore piling

Survey of numerical methods in offshore piling : Smith, I M Proc Conference on Numerical Methods in Offshore Piling, London, 22–23 May 1979, P1–8. Publ London: Inst Civil Engineers, 1980

Survey of numerical methods in offshore piling : Smith, I M Proc Conference on Numerical Methods in Offshore Piling, London, 22–23 May 1979, P1–8. Publ London: Inst Civil Engineers, 1980

Numerical methods in offshore piling. Proceedings of a conference organised by the Institute of Civil Engineers and held on London, 22–23 May 1979 : London: Institution of Civil Engineers, 1980, 215P

Numerical methods in offshore piling. Proceedings of a conference organised by the Institute of Civil Engineers and held on London, 22–23 May 1979 : London: Institution of Civil Engineers, 1980, 215P

The Heather Platform Leg Repair

This case history reviews the analysis and repair of a corner leg of the Heather A platform; damage was caused by a foundation pile dropped during installation. The paper describes the stereophotographic and mechanical templating techniques used to verify shell deformations. The choice of a mechanical solution and the interface with module installation and commissioning are reviewed. Introduction The Heather field is located in Block 2/5 of the U.K. sector of the North Sea (Fig. 1). The Heather A platform is located at 0 degrees 56'22.53" longitude and 60 degrees 57'13.51 "latitude, approximately 100 km (64 miles) east of the northern end of the Shetland Islands in 143 m (470 ft) of water. The oil field was discovered in Dec. 1973, and a steel-pile-supported platform was selected to develop the discovery. With the availability of larger pile-driving hammers, the decision was made in the fall of 1975 to drive 1.52-m (60-in.) diameter piles. Each of the 24 piles [96 m long × 64 mm thick (315 ft × 2.25 in.) and 218 Mg (240 tons)] is made from a 64-m (210-ft) lead section with a 32-m (105-ft) extension welded offshore. During the offshore piling operations in the summer of 1977, one of the piles had been joined and was being held by the derrick barge in preparation for lowering to the seabed, then one of the shackles linking two sections of slings broke. The pile, laterally restrained in the guides, dropped more than 40 m (130 ft) in almost free vertical fall before hitting the jacket at the location shown in Fig. 2.The extent of the damage posed a potentially serious setback to field development. With the reduction of load-carrying capability of the platform, the complete module installation program was reanalyzed. The selection of the repair method was judged in line with performing the repair during the winter period. A limited number of modules were installed on the platform by mid-Oct. 1977, when the repair operation commenced from the semisubmersible vessel Treasure Hunter. The first phase of the repair was completed by mid-Jan. 1978, and the second phase from mid-April to the end of May finalized the repair.This paper traces the stages of design, repair, and techniques developed and appraises the interface with the remainder of the development. Description of Damage Initial impact of the pile was at the cone-shaped section of the "bottle" where the leg diameter increases from 2.5 to 5.7 m (8 to 18.5 ft). The pile glanced off the cone, buckling the 40-mm (1.625-in.) thick plate and punching a hole [approximately 1.25 × 1 m (4 × 3.5 ft)] in the cylindrical shell. At the junction of the cone and shell is a critical ring stiffener designed to contain the hoop stresses at this change in section. This ring stiffener was torn in two places, and the tongue section in between was bent downward. As the pile fell, it continued to dent the cylindrical shell up to 200 mm (10 in.) radially and caused further damage to a second lower ring stiffener. Denting of the vertical shell was caused over some 4.5 m (14.5 ft). JPT P. 569＾