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Paper Number 3011-MS
Title OCEAN IMPLOSION TEST OF CONCRETE (SEACON) CYLINDRICAL STRUCTURE
Authors Roy S. Highberg and Harvey H. Haynes, Civil Engineering Laboratory
Source

Offshore Technology Conference, 2-5 May , Houston, Texas
Copyright 1977. Offshore Technology Conference
Language English
Preview ABSTRACT

An ocean implosion test was conducted on a pressure-resistant concrete cylindrical structure to obtain the depth at implosion. The structure was a reinforced concrete cylinder with hemispherical end caps, twenty feet (6.1 m) in overall length, ten feet (3.05 m) in outside diameter, and 9.5 inches (241 mm) in wall thickness. The structure was near-neutrally buoyant having a positive buoyancy of 12,000 pounds (5.4 Mg) for a hull displacement of 85,000 pounds (38.5 Mg). The implosion depth of the cylinder was 4700 feet (1430 m). A predicted implosion depth, using an empirical design equation based upon past test results, was 16 percent less than the actual implosion depth.

INTRODUCTION

A pressure-resistant, reinforced concrete hull was constructed in 1971 as part of a Seafloor Construction Experiment, SEACON I. The structure was placed on the seafloor at a depth of 600 feet (180 m) for 10 months. Figure 1 shows the SEACON I hull prior to its ocean emplacement. Since its retrieval in 1972, it has been located in the open air about 150 ft. (50 m) from the ocean. In the summer of 1976, the structure was returned to the ocean for an ultimate load test, that is, the structure was lowered into the ocean until implosion.

SPECIMEN DESCRIPTION

The cylindrical structure was assembled from three precast, reinforced concrete sections. The straight cylinder section, 10.1 feet (3080 mm) in outside diameter by 10 feet (3050 mm) in length by 9.5 inches (241 mm) in wall thickness, was fabricated by United Concrete Pipe Corporation. The concrete hemisphere end-closures, 10.1 feet (3080 mm) in outside diameter by 9.5 inches (241 mm) in wall thickness, were fabricated in-house. Tolerances on the sections conformed to concrete pipe standards of not to exceed to ±0.75 inch (19 mm) for the inside diameter or minus 0.5 inch (13 mm) for the wall thickness.

Steel reinforcement in the amount of 0.70% by area was used in both the axial and hoop direction. Reinforcing bars of 0.6 inch (15 mm) diameter were employed throughout the structure. A double circular reinforcement cage was fabricated for each precast section; the concrete cover on the outside and inside reinforcing cage was 1 inch (25 mm). For the cylinder section, hoop rebars had a spacing of 27.25 inches (692 nm) and 31.25 inches (794 mm) for the inside and outside cages respectively.

The hemispherical end-closures were bonded to the cylinder section with an epoxy adhesive, no other attachment besides the epoxy bond was employed (Figure 2). The gap between the mating surfaces of the hemisphere and the cylinder was less than 0.13 inch (3 mm) for 75% of the contact area. Prior to epoxy bonding, the concrete surfaces were prepared by sandblasting and washing with acetone.

Source: http://www.onepetro.org/mslib/servlet/onepetropreview?id=OTC-3011-MS&soc=OTC

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Offshore Technology Conference, 2-5 May 1988, Houston, Texas
Copyright 1988. Offshore Technology Conference
Language English
Preview ABSTRACT

The U. S. Naval Civil Engineering Laboratory has developed formulas to predict the collapse of hollow concrete spheres or cylinders and has shown that they can remain watertight under the pressure of chemically active deep ocean seawater. This paper tabulates wall thickness, volume of concrete, weight of displaced water, and gives a concrete cost factor for several interior dimensions of one-atmosphere habitats or valve chambers for oil and gas wells, and describes a low-cost method for building submersible concrete structures by shotcrete laminating in floating formwork.

INTRODUCTION

The need for a "shirtsleeve" environment for workmen servicing subsea oil and gas wells has long been recognized, and by 1969 the Lockheed Missiles and Space Company had constructed a seafloor pressure chamber called a "wellhead cellar" of steel designed to be lowered from the surface and connected to each well in the undersea field (1). More recently, a study was made on the feasibility of a one-atmosphere subsea collection, test, kill, and transport system for controlling and delivering gas from multiple wells in the Troll field off Norway in 1,115 ft. of water (2). Access to the subsea chamber is via a lift inside a slender steel nonarticulated tube "monopile" which provides a continuous atmospheric connection with the surface and supports a helideck.
In the past 20 years more than 60 undersea habitats have been deployed for scientific research, or for military, commercial, and recreational use. More are needed, and concrete is the cheapest and most durable material for marine use, but innovative building methods are required to make concrete economically feasible as a substitute for welded steel construction. This paper presents new methods and concepts for using concrete offshore.

BACKGROUND

In order to determine the long-term durability of concrete in the deep ocean, the U. S. Naval Civil Engineering Laboratory immersed 18 concrete spheres in the Pacific Ocean at depths ranging from 1800 to 5000 ft. Each sphere was 66 inches in diameter with 4-inch thick walls and was designed for a working depth of about 3000 feet at 1300 psi.
The design strength of the concrete was 8000 psi but after 5 years, tests showed a 15 percent increase. This remained the same after 10 years. No visible deterioration of the concrete was observed in any of the spheres and leakage varied from 0 to only 14 gallons after 10 years.
Spheres immersed beyond the designed depth collapsed and a formula was developed to predict the wall thickness needed for concrete spheres and cylinders of various outside diameters to survive at various depths (3). The authors contemplated that in the future, methods may be developed to build massive structures on the seafloor at which time it would be desirable to have designs for negative buoyancy and deeper depths.

Number of Pages 4

Where were you born?
Vancouver, British Columbia, Canada. It’s still
my home today.
What is your occupation?
President of Nuytco Research Ltd.; of Can-Dive
Ltd.; of Hardsuits Inc.; and of Seagraphic
Publications, which includes manufacture and
operation of deep-diving submersibles
(DeepWorker); construction and offshore
commercial diving contractor manufacture and
operate one-atmosphere diving suits (Newtsuit/
Inventor, entrepreneur, explorer, president
and founder of Nuytco Research Limited and
Can-Dive Services Limited. An internationally
recognized pioneer in the diving industry, Phil
Nuytten has spent 40 years creating deepwater
dive products that have opened the ocean’s
depths to exploration and industry. His goal has
been to provide scientific, technical, military,
and sport divers full access to continental shelf
depths without the hazards of decompression,
so that humans can explore, learn about, and
protect the world’s oceans.
Qwith&A
R..T.. (Phil) Nuytten
Exosuit); and publisher of Diver magazine, the
longest-established scuba diving magazine in
North America.
Why did you choose your career path?
I began diving in 1952-53 as a very young boy.
Diving equipment was expensive and hard to
get, so I made much of my own equipment. I
started the first Scuba shop in western Canada
when I was 15 years old and ran it after school
and on weekends. I did a lot of light salvage and
recovery work on the side and made the decision


to become a commercial diver. The rest followed.
What is your personal motto?
In commercial underwater work, my motto has
always been “Safety, performance, profit” –
strictly in that order.
What hobbies do you enjoy when you are not
working?
Northwest Coast native art: collecting old
pieces and carving/engraving new work. Sound
engineering and song writing. Collecting
historical diving equipment and over-seeing
(as president) the Historical Diving Society
– Canada. Writing books, monographs and
technical papers on native art and diving.
What are some of your career highlights?
Invention of the Newtsuit ADS, DeepWorker
submersibles, and Remora Submarine Rescue
System, and the acceptance of these devices as
standard equipment in the U.S. Navy and other
navies, world-wide. On the commercial side,
the co-founding of Oceaneering International
Inc. in 1969.
What do you like most about your job? The least?
I like coming up with innovative solutions
to difficult problems and so that’s what my
team and I do. My least favourite thing is
bureaucracy in all its insidious forms.
What are some of the biggest challenges your job
presents to you?
The biggest current problem is how to get all
of the things I want to do – and plan to do –
actually done before they pack me off, drooling
and babbling, to the ‘home.’
What advancements in undersea technology have
you witnessed during your career? Is there one
that proved most beneficial to you?
Probably the most dramatic advancement I’ve
been privileged to witness, generally, is the rise
of electronics. More specifically, the advent of
the digital revolution.
What new undersea technologies would you like
to see?
My pet ‘big project’ is called “Vent-base Alpha”
and comprises a self-contained one-atmosphere
undersea habitat built around a ‘black smoker’
(a subsea heat vent). The vent would power
a giant stirling cycle engine to produce power
and an artificial ‘sun.’ Inhabitants would be
under normal pressure inside the habitat
and would use one-atmosphere systems like
DeepWorkers and Exosuits to go to work
outside the habitat. The ‘work’ would be
mining the highly mineralized heat vent fluids
for laboratory-pure metals, which would
produce a revenue stream for the habitat.
(Check out ‘Phil Nuytten – Nextfest’ on
Youtube for more info.)
What does the future hold for you?
Definitely the “Vent-base Alpha” project.
The immediate future is to finish the Exosuit
prototypes and then make test units available
to scientific institutes, marine contractors
and diving schools. My objective is to switch
deep-diving – both work and exploration –
over to one-atmosphere. Using the armour of
technology is the only way we fragile critters
can greatly exceed our biological design
limitations and get to colonize the deep
oceans of this planet.
What does the future hold for the ocean
technology industry?
Unless we figure out a way to make the planet
bigger, we must ultimately move back into the
oceans. At that juncture, the ocean technology
industries will come into their own in a big
way. In the interim, this sector continues to
grow at a healthy pace, year after year. This
is an incredible contrast to that long ago time
when I was a high school student wondering
how I could make some sort of a living in the
undersea field. The sub-sea opportunities now
are a hundred-fold greater and I believe they
will continue to accelerate.
What advice do you have for people just starting
in the industry today?
I envy you! My advice is to select a broad field
of undersea interest: science, military,
construction, research, sport, education, etc.
Then keep narrowing it down until you find
the exact niche that suits – then go for it.

source:

http://www.journalofoceantechnology.com/

The technology behind the NEWTSUIT was changing, and the suits themselves were highly expensive to produce. 

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One of Canada's top diving innovators and pioneers speaks intelligently about deep sea diving and submersibles when discussing the future of his industry, but it is his most recent endeavour that truly makes his eyes sparkle.


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