Pile-supported Platforms Research Articles

Field testing and numerical analysis on performance of anchored sheet pile quay wall with separate pile-supported platform

The anchored sheet pile quay wall with a separate pile-supported platform was invented to meet the functional and serviceable requirements of engineering practice, including the higher elevation of retained soils and smaller wall deflection, based on the conventional anchored sheet pile structure. This paper presents the field testing as well as the three-dimensional numerical analysis on the first practical case of the new structure. The performance of the structure and soil is described and discussed, including the lateral deflection, bending moment, axial force, tensile force, and lateral earth pressure. The measured data and computed results show that the lateral deflection of the sheet pile wall can be significantly reduced, and the measured maximum lateral displacement is approximately 0.21% of the wall height in this case. The bending moment and axial force of the supporting piles are generally greater than those of the sheet pile and anchor wall, indicating that the pile-supported platform is efficient for reducing the loads acting on a sheet pile. The effects of the pile-supported platform can be summarized as a combination of blocking effect of the supporting piles to carry the lateral earth pressures as well as a load-relieving effect of the platform to transfer the vertical loads to deeper foundation soils through the pile. Compared to the numerical results, Coulomb's earth pressure theory significantly overestimates the earth pressure loads acting on the sheet pile at higher elevations. Furthermore, the dredging activity has greater effects on the behaviours of the sheet pile wall and front-pile than the superstructure construction.

Large-scale tests of pile-supported earth platform with and without geogrid

In recent years, concrete piles, such as cast-in-place piles and precast concrete piles, have been increasingly used to support superstructures and embankments when they are constructed on soft soils. On the top of pile head elevation, a certain thick granular cushion including geosynthetic reinforcement is usually installed to transfer more external load onto the piles through soil arching effect and membrane effect. This technique involving the use of rigid piles, gravel cushion and geosynthetics is usually referred to as geosynthetic-reinforced and pile-supported earth platform. This paper presents two well-instrumented large-scale tests of pile-supported earth platform with and without geogrid reinforcement. The performance of the pile-supported platform with geogrid and its load transfer behavior were investigated and compared with those for the test without geogrid. The validation of the EBGEO (2010) calculation was performed based on the test results. The test results indicate that under lower applied load, the loads carried by the piles in the test with geogrid were close to those in the test without goegrid, while with an increase in external load the loads carried by piles in the test with geogrid increased faster than those in the test without geogrid. The negative skin friction for the test with geogrid was smaller than that for the test without geogrid. Based on the contours of earth pressures on foundation base the maximum earth pressures were distributed along the edge of central cap in the test with geogrid. The minimum earth pressures were on midway subsoil between two caps in both tests. Based on the test results, the efficacy for the test with geogrid was 2.5% greater than that for the test without geogrid at the end of loading. The efficacies predicted by the EBGEO (2010) calculation agreed well with the measured efficacies.

The Distribution of Shallow Water Juvenile Fishes in an Urban Estuary: The Effects of Manmade Structures in the Lower Hudson River

The objective of this study was to determine what effect, if any, large pile-supported platforms (piers) have on the habitat distribution and abundance of juvenile fishes. Trapping techniques were used in 1993 and 1994 under piers, in pile fields, and in open-water habitat types in shallow areas ( 20,000 m2) is probably poor for YOY fishes when compared with nearby pile field and open-water habitat types.

Earthquake Criteria for Platforms in the Gulf of Alaska

This paper describes earthquake criteria for platforms in the Gulf of Alaska. The effects of strong earthquake ground motions are determined by the dynamic response characteristics of the soils and attached structures. The design of the structures to resist extreme wave loadings has an important influence on these characteristics. Introduction The offshore industry is on the threshold of a significant challenge - the timely, safe, and economic development of the Gulf of Alaska oil and gas reserves. This area is swept frequently by severe storms that generate waves and currents rivaling those of the North Sea and North Atlantic. In addition, the area is bordered by the earth's most active seismic zone, the Circum-Pacific Belt. Some of the world's largest recorded earthquakes have occurred on the perimeter of the Gulf of Alaska. perimeter of the Gulf of Alaska. This paper focuses primarily on the second major environmental loading threat - earthquakes. Using concepts, background, and data presented at the Seventh Annual Offshore Technology Conference, this technology is synthesized in the framework of a reliability analysis to help define earthquake ground-motion criteria for pile-supported drilling and production platforms. Summary 1. Depending primarily on location and type of soilfoundation condition, elastic design level earthquake motions producing peak effective ground velocities in the range of 50 to 70 cm/sec (20 to 28 in./sec) are indicated. To produce the desired level of loading and superstructure-foundation characteristics, a design wave height of approximately 120 ft is suggested along with the application of API RP 2A member-sizing guidelines. These results are applicable to the type of platform, design procedure, and analytical models used in this study. Design criteria are intended to be platform-system, strength-determining parameters. In an environment like the Gulf of Alaska, where there may be multiple environmental threats that produce loadings of comparable magnitudes, design criteria for one threat should not be selected without explicit consideration of other threats. 2. The potential force effects developed by severe ground motions on pile-supported platforms are very different from those caused by intense wave and current action. While loading patterns may be similar, one loading system fundamentally is force-limited (earthquakes) and the other is load-unlimited (wave and currents). As earthquake ground-motion intensity increases, the amount of transmitted load is limited by the ability of the foundation elements and soils to transmit that energy to the platform. In contrast, as wave-current action increases, the platform. In contrast, as wave-current action increases, the amount of imposed load essentially is unlimited. 3. Two fundamental efforts are identified that should be a focus of engineering research in this general area of technology. First, strong ground motions should be recorded at offshore sites in the Gulf of Alaska. Such records could be used to determine the applicability of attenuation and local soilgeology modulation relationships that describe the effects of distant earthquakes on a given location. No measurements have been made of strong ground motions offshore. JPT P. 325

A Subsea Completion System for Deep Water

Abstract As the search for oil and gas reserves is extended to deeper water, conventional offshore exploitation methods become less attractive due to the high cost for fixed platforms. This has prompted consideration of subsea completion methods as an alternative development technique. Humble Oil and Refining Co. has conducted tests to develop technology and equipment needed for completion and production maintenance of satellite underwater wells in deep water. Results of this development program are presented. Introduction The development of offshore oil and gas fields has largely been conducted from permanent pile-supported platforms using directional drilling techniques. Wells are drilled through large diameter conductors and wellhead equipment is installed on the platform deck. Permanent-type platforms have been installed in water depths to 285 ft. As activity moves into deeper water, the investment required for fixed platforms increases rapidly. This has prompted consideration of alternate development techniques for deep water using floating drilling and subsea completion methods. Floating rigs have been widely used as a deep water exploratory tool and techniques and equipment are now in an advanced state of development. For example, Humble recently drilled an exploratory well from a floating vessel in 632 ft of water offshore California. Industry experience is rather limited, however, with the completion and production of underwater wells. Most have used adaptations of conventional land equipment and have been completed in water depths easily accessible to divers. The extension of offshore operations to the edges of the continental shelves, and even beyond, has accelerated interest in the use of subsea completion techniques. To provide the technology and equipment needed for the completion and production maintenance of satellite underwater wells in deep water, Humble has prompted development ofan underwater well completion system,an underwater Christmas tree system, andthe tools and techniques required for performing well servicing and simple workover operations from a remote location. All equipment has been designed for remote diverless installation and operation. As a part of this program, an off. shore underwater test well has been completed and production experience has been accumulated over an extended period. Underwater Well Completion System The well completion system for satellite underwater wells (Fig. 1) was designed so that routine production maintenance and simple workover operations could be performed from a remote location with access to the well tubing through the flowline. JPT P. 1049ˆ