bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rescue of Diver Under Pressure
Authors: Galerne Andre 
Published: October 2008

ABSTRACT
As divers plunge deeper under saturation conditions, they face increasing dangers as any illness or injury becomes a tremendous threat to their lives because of the limited medical treatment that can be provided to the diver during decompression at a remote site or on offshore rigs. In addition, in the case of an emergency rig evacuation, divers under pressure are helpless.
The above problems have been solved by a helicopter diver-under-pressure-transfer system, developed by IUC and recently demonstrated under simulated emergency conditions. The successful demonstration has shown for the first time that a diver or divers could be safely and rapidly transported while under pressure from a remote site (in this case ''Venture Two", a rig in the North Sea) to IUC?s North Sea Hyperbaric Center at Aberdeen, Scotland.
The major design criteria that the complete system weigh less than 2,600 lb and withstand an internal pressure equal to 750 ft was achieved by the engineers at Southwest Research Institute by sing a titanium alloy combined with sophisticated titanium welding techniques perfected by the manufacturer, TIFAB.

INTRODUCTION
In the North Sea oil fields, among the most dangerous diving conditions in the world, divers are called on to perform heavy construction tasks at deeper depths each year. As the working depths of the divers increase along with increasing number of divers employed in deep work, the risk of serious injury to a diver increases. With men living at pressure for weeks at a time, the increasing use of saturation diving makes the possibility of a medical emergency, such as appendectomy, heart attack, head injury, perforated ulcer, burns, infections, bodily injury, or accidental amputation, a major concern.
An injured or sick diver who had been working at 200 m would face at least a week's decompression eliminating the possibility of an immediate transfer to a shore-based hospital. Any effort to decrease the decompression time would jeopardize the diver's condition seriously; in fact, sound medical practice would be to prolong decompression due to the unknown effects of decompression on damaged tissues or organs. In cases where the victim's survival depends on immediate surgery or intensive care the only possibility that had existed was to location a qualified doctor and fly him and the necessary medical equipment to the rig. While some people feel that surgery or intensive medical care can be performed in the rig's deck decompression chamber the majority of people are of the opinion that offshore decompression chambers are not ideal locations for providing medical attention. Excessive noise vibration, possibly poor communications and lighting plus the limited equipment, space, and the poor hygienic conditions would result in a very high probability of failure and result in death or permanent injury to the diver.
High Accuracy Directional Surveying Of Wells Employing Inertial Techniques
Authors: Morgan D.G. , Scott A.G. 
Published: October 2008

ABSTRACT
Drilling of multiple wells from offshore platforms has greatly increased the accuracy requirements for directional surveying. To meet this need a 3-dimensional method of surveying deviated wells to within one foot to the 13 3/8" Casing Shoe has been developed. The basis of the equipment is an inertial system which consists of a gyro stabilised instrument cluster with three accelerometers measuring the displacements. The advent of Inertial techniques offers the opportunity to complement, monitor and improve conventional survey techniques.

INTRODUCTION
The drilling of multiple wells from offshore platforms has greatly increased the accuracy requirements for directional surveying. Conductors are commonly drilled with seven or eight foot spacing and the accuracy required in this situation is essentially beyond the capability of conventional directional surveying equipment. With such spacings between wells the possibility of well collision cannot be excluded particularly since the density of wells may increase in future.
One may anticipate an increasing loss of production during concurrent drilling and production operations due to the uncertainty of hole position.
The need to define the bottom hole position in cases of loss of well control has increased. The source of concern arises from the doubts about the accuracy of conventional surveys and the doubt that the position of a deep well could be known within the detection range of homing devices.

TECHNOLOGY
Taking the original premise - that there is concern and doubt about the accuracy of conventional surveys - a premise which will not be rigorously evaluated in this paper but which surveys will endeavour to illustrate - the first question which arises is to define alternate systems.
Reliability and accuracy of gyro systems has existed for aircraft navigation and a natural progression arose to examine the more sophisticated navigation systems of military and commercial aircraft.
Sophisticated inertial navigation systems were developed in the 1960's for missiles and all weather combat aircraft. More recently they were applied as survey equipment in the artillery and topographical surveys. The navigation performance for aircraft is typically 1 nautical mile per hour - accuracy sufficient to assist transatlantic crossing the system is, however, capable of increased accuracy under different operating conditions.

THE SYSTEM
An Inertial Navigating system can be defined as one which is independent of information from outside the system except for gravitational effects.
The System consists of five main parts:Inertial platform containing accelerometers and gyroscopes mounted on three gimbals.Electronics control and computing system which processes the output signals from the inertial platform and calculates displacements and monitors the servos which stabilise the inertial platform.CDU (Control and Display Unit) which performs two-way communication between the system and the operator when initiating the system.Random Access Memory store for data storage.
Re-Examination Of P-Y Curve Formulations
Authors: Stevens J.B. , Audibert J.M.E. 
Published: October 2008

ABSTRACT
In the analysis of piles supporting offshore structures, the key element in predicting the response to lateral loads is the determination of the appropriate lateral load - deformation relationships (p-y curves) for the soil. The present practice of constructing p-y curves is based on the results of lateral load tests on instumented piles and strength-deformation characteristics of the soil. (Matlock,1970; Reese et al, 1975; and API RP 2A, 1978)
A study was undertaken to compare the results from lateral load tests on piles up to 59 inches in diameter driven in soft to medium clays to that predicted using the above ways of constructing p-y curves.
In general, it was found that the predicted pile deflections were significantly greater than the observed deflections. Also the maximum bending moments were underestimated.
Two factors were identified as sources of the differences; The first was the assumed linear dependence of the soil-deformation characteristics on pile diameter. The second was the lateral soil resistance at shallow depths was greater than those given by the empirical methods.
Based on the study results, modifications are suggested to the present methods of constructing p-y curves.

INTRODUCTION
P-y curves are generally used to characterize the lateral soil resistance-deformation relationship for piles supporting offshore structures. These curves are related to the strength-deformation characteristics of the soil as obtained from conventional soil tests. The methods of constructing p-y curves for clays are empirically derived from the results of lateral load tests on instrumented piles.
The use of empirical methods for design purposes is justifiable when the design conditions approximate those upon which the method is based. One of the important considerations in using empirical methods in geotechnical engineering is the scale effect. Ideally the size of the test element should be the same as the actual element. However, in most cases, it is impractical to perform a full scale test.
The methods presently used for constructing p-y curves for clays were based on piles having diameters ranging from 6 to 24 inches. With the trend of installing platforms in deeper waters and more hostile enviroments, piles with diameters ranging from 5 to 8 feet are common. An extreme example is a number of 15-ft diameter piles driven in the Scheldt River delta to support a cable way. (Lubking, 1977) Piles of these diameters are much larger than those upon which the empirical methods are based.
Lateral load tests on instrumented piles comparable to those presently used offshore have been published. In addition, other researchers have presented results which suggest ways to account for scale effects. This paper compares the test results to those predicted using the present methods of constructing p-y curves and suggests some modifications.
Piezometer Measurement For Deep Penetration Marine Applications
Authors: Preslan W.L. , Babb L.L. 
Published: October 2008

ABSTRACT
Design analysis and planning for installation of offshore structures requires information about the pore pressures in the foundation soils. Pore pressures may be used to calculate effective stresses for use in the study of slope stability, for bearing capacity studies of gravity structures, and for the evaluation of axial capacity of piles. Also, pore pressure information is required for hydrogeologic studies.
A special piezometer has been manufactured for measurement of pore pressures at deep penetrations in sand or clay soils arid has been used at offshore sites in the Gulf of Mexico. The device will operate to pressures amounting to over 2000 ft of seawater and has been used successfully at a penetration of 200 ft in a water depth of over 650 ft. The accuracy is generally within two feet of head of seawater. The piezometer and installation system are believed to be unique and the measurements are believed to be the first of their kind in deep-water applications.
The piezometer and its operational characteristics are described and practical applications and field data are presented. The influence of the borehole and installation method on the measured pore pressure is analyzed, and techniques for estimating in situ values from short term tests in clays are presented. The influence of in situ gas on the-measured pressure is examined along with geochemical methods of evaluating the concentration, physical state and probable effect of that gas.

INTRODUCTION
The application of effective stress techniques in marine geotechnical investigations is currently hindered by the difficulties inherent in measurement of the pore water pressures that may exist within in situ marine sediments. To date, measurements in the marine environment have generally been in shallow water and the piezometer tips have been installed to relatively short penetrations below the seafloor. When effective stress analyses nave been attempted for projects involving large thicknesses of sediment, the in situ pore water pressure has been estimated using correlations with other more easily measured parameters.
This paper describes a wire-line piezometer that has been used to measure in situ pore water pressures in the course of routine offshore geotechnical investigations. Such investigations are typically carried out from an anchored vessel using a rotary drilling rig to advance a borehole below the seafloor. At specified penetrations below the seafloor, a wire-line sampling tool is lowered down the inside of the drill pipe and out the open-center drill bit to sample the relatively undisturbed sediment below the bit. At selected locations between sample intervals or at the conclusion of sampling operations the wire-line piezometer described here is lowered through the drill pipe and inserted into the sediment below the bit. The pore water pressures sensed by the piezometer are transmitted to recording devices on the vessel via the wireline.
Small Scale Tests For The Determination Of P-Y Curves In Layered Soils
Authors: Allen Junius D. , Reese Lymon C. 
Published: October 2008

ABSTRACT
Preliminary results of a series of lateral-load tests on a small-scale pile in layered soils are presented. The major objective of the tests was to measure soil resistance p as a function of deflection y along the length of the pile in a stiff upper layer. The soil profiles all consisted of a stiff, cemented clay overlying a soft clay with the thickness of the stiff layer being different for different tests. The pile was loaded transversely a short distance above the soil surface and measurements of moment along its length were made for each load increment. Deflection and slope at the top of the pile were also measured.
Measured load-deflection curves are compared to load-deflection curves computed by using p-y criteria for homogeneous soils. The results indicate that the p-y criteria used for the analyses give consistently reasonable or conservative results. Further analyses of the test results are expected to show the effects of layer thickness on the resistance offered by a stiff surface layer to lateral pile movement and assist in the development of guidelines for predicting pile behavior in layered soils.

INTRODUCTION
Pile foundations in the marine environment are frequently subjected to lateral loading due to wind, wave, tidal current, ship impacts, and submarine slope movements. Accurate estimates of foundation response to such loads allow more economic design of foundations and superstructures. A method of analysis which is now in widespread use for predicting the behavior of laterally loaded piles involves the solution of the fundamental equation of beam bending,
(Available in full paper)
The equation can be expressed' in finite difference form and a digital computer is essential for solution of any realistic problem. The soil resistance as a function of deflection is expressed in the form of p-y curves. Criteria for constructing p-y curves have been presented by Matlock (1970) for soft clay, Reese et a1. (1975) for stiff clay below the water table, Welch and Reese (1975) for stiff clay above the water table, and Reese et al. (1974) for sand. These authors have presented recommendations for both static and cyclic loading. Gill and Demars (1970) have presented a set of p-y criteria for static loading.
Most of the p-y criteria were based on the results of one or several lateral load tests in fairly homogeneous soils, coupled with earth pressure theory. Results of analyses based on the criteria for homogeneous soils have been compared to additional field load test results by Stevens and Audibert (1979), Bushan et al. (1979), Ismael and Klym (1978), Lee and G1lbert (1979), and Meyer (1980). Suggestions for modifications have been made by Stevens and Audibert (1979), Lee and Gilbert (1979), Meyer (1980), and Sullivan (1977). The evaluations which the p-y criteria in homogeneous soils have undergone have brought some degree of confidence to the use of these methods.
A Riser Angle Positioning System (Raps)
Authors: Dean Quenton W. 
Published: October 2008

ABSTRACT
A system has been developed to provide adequate position reference backup for a dynamically positioned vessel's primary position reference. This system employs two or more riser angle indicators, one located at the top and one at the bottom of the riser with any additional sensors located at intermediate points along the riser. A mini-computer, either a DEC PDP-8E or a PDP-ll-03L, is required to compute the vessel offset from the target using the riser angle data. The system was tested aboard the Discoverer Seven Seas drillship in 4,876 feet of water off of St. Johns, Newfoundland on August 15, 1979, and has been used aboard the ship since. This ship is positioned by a Honeywe11 Automatic Station Keeping (ASK) system uti1izing the Honeywell RS-sB acoustic position reference system as the primary position reference.
With the aid of the test results and the operation al data, the performance of the Riser Angle Positioning System (RAPS) and the theory of operation will be presented in this paper.

INTRODUCTION
RAPS is an integrated reference system employing the hard wired angle sensors and the primary acoustic reference system. Response from the lower riser angle indicator system originally supplied by Honeywell as a backup system to the acoustics has become increasingly suspect while drilling in water depths greater than 2000 feet. The shallow water acceptance of the taut wire system employed on other Dynamic Positioning System (DPS) vessels led to the development of RAPS using both a top and bottom riser angle indicator to provide reliable position references in up to 6000 feet water depth. The inertial reference systems being offered by certain manufacturers also led us to consider using the motion within the riser as an aid in determining the position of the vessel. The excellent performance of the RS-SB system encouraged-an adaptive system that would provide bumpless transfer between RAPS and the RS-5B system.
The, basic design objectives of the integrated reference system, RAPS, were:To develop an algorithm capable of determining the location of the end of the riser with respect to the top of the riser knowing at least the angle and bearing at the top and bottom of the riser.To develop algorithm constants by comparing the calculated position to a known position i.e. the RS-sB data.To adhere to a "no one sing1e fau1t wi11 cause a drive off" design objective. This would require extensive filtering and logic to determine the RS-sB data valid before altering the algorithm constants. It would also require logic to validate the riser angle raw data and the calculated RAPS data.

COMPONENT SET-UP (ASK-RAPS)
The importance of having accurate, reliable signals can not be over emphasized. The ASK has held position excellently on the position reference it has received. However, it has been the stability of the position references which have led to the development of RAPS.
Predicting The Drivability Of Large Diameter Offshore Piling
Authors: Lang George R. 
Published: October 2008

ABSTRACT
Large diameter piling are increasingly being used in offshore structures to house the well conductors. In order to predict the drivability of these large diameter members, it is desirable to utilize the wave equation theory developed by Smith and others, which has been used for a number of years to examine the drivability of conventional piling. This paper examines the questions:"Does the wave equation theory accurately predict the drivability of large diameter piling?" and"If so, what variations from the standard input data are required?"
Three recently installed structures were analyzed and the predicted blow counts and driving stresses were compared to those measured in the field. The first of the structures was a 96- to l68-inch diameter, tapered, self-supporting caisson, and the other two were mudslide platforms with l25-inch diameter piling. Two variations from the standard Smith input data were required to predict the drivability of these piles. The first variation was a result of the fact that large diameter piling will usually require a tapered drive head because of the smaller diameter of the standard pile cap. In addition, large diameter caisson well protectors are usually tapered above the mudline to make more efficient use of the steel. Formulas were derived to simplify calculation of the stiffness and weight of a tapered, non-prismatic pipe segment. Then a study was made comparing the use of tapered drive heads with standard pile caps to the use of a special large diameter pile cap. The second variation from the standard input data is related to the problem of soil skin frictional "set-up" and end bearing resistance. The wave equation theory was found to accurately predict the drivability of large diameter piling with only a slight variation from the standard Smith method of analysis.

INTRODUCTION
Special precautions are sometimes taken to protect the well conductors in an offshore drilling platform. One way of protecting the wells is by housing them inside a large diameter member. In a mudslide structure, the piling may serve the dual purpose of supporting the platform and housing the wells to protect them from unstable soil movements. In some situations a self supporting caisson well protector can be used in lieu of a platform to support the well cluster when dynamic or fatigue problems exclude the use of self-supporting well conductors. The caisson may be a constant diameter pipe or the more efficient tapered member.
The design engineer must determine the answer to two questions. He must decide whether or not the pile can be driven to the design penetration or if drilling or jetting will be required. Secondly, he must be able to predict the driving stresses induced in the pile. New massive hammers are available and the engineer needs to know whether a large hammer is required or if a smaller and cheaper conventional hammer will suffice. Naturally, the engineer would like to utilize the one dimensional wave equation for the evaluation of the drivability of large diameter piling.