Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention rela-~es to ~ support structure especi~lly
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for use i n under water work .
Foundation work in under-wa-ter constructions is
usually complicated and expensive. When a support structure
is -to be placed upon the bo-t-tom of a harbour, river, a-t sea,
or in a watercourse, where piledriving is no-t required, a
bed of gravel or crushed ma-terial (macadam) is usually laid
upon the bottom. This bed must be carefully leveled, so to
be even and horizontal. ~his is difficult work because of
the depth of the water, which may b~ considerable, and -the
reduced sight at such depth.
Gravel and crushed stones have different angles of
repose, depending upon the size and -the shape of the par~icles
(-the fraction), as well as the nature of the rock material.
If a mound of macadam is subjected to a modest, evenly applied
load, say S tons/square meter, the natural slope, determined
by the angle of repose will remain unchanged under the load.
The macadam becomes only slightly compressed. If macadam is
dis-trlbuted throuyh a tube upon a horizon-tal substratum, a
conical mound is obtained, which covers a circular base area,
and has a sloping envelope surface with an even contour.
This i5 true, even if the bottom is uneven or slightly in-
clined.
The present invention simplifies the forming ofsuch mounds of material having internal friction in exactly
desired positions~ and to utilize the same as foundations for
~30 support structures.
The present invention provides a support structure
erectable upon a bed of friction material, for instance
macadam, and is especially suited for use where it is, at
least partly, submerged below a body of water.
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A me-thod for erecting such a support s-truc-ture com-
prises formi.ng a rigid, ~ollow pillar and attaching to one
end thereof a reversed, li kewi se rigid funnel-shaped struc-
ture, locating said pillar substantially vertically with the
hase of said funnel-shaped structure about level with the
bottom below said body of water, and filling a ma-terial
having i.nternal friction into said funnel-shaped s-tructure
and up in the pillar by way of said hollow pillar, the base
angle of said reversed funnel-shaped structure exceeding the
anyle of repose of the material.
A support s-tructure according to -the invention com-
prises a rigid, hollow pillar, which at its lower end merges
into a reversed, likewise rigid, funnel-shaped struc-ture
having a base area noticeably larger than the cross-sectional
area of the pillar, and a-t which the base angle exceeds -the
angle of repose of material having internal friction used.
The internal sur~ace of the funnel-shaped structure
will thus be extensively supported by -the cone of macadam,
which transfers the load from -the support structure to -the
bottom.
In order to ensure an exact forma-tion of the cone
of macadam the tubular pillar may be provided with a restric-
tion providing a centrally located passage adjacent to thetransition between the pillar and the pillar s-tructure.
Furthermore, the funnel structure at its base may be provided
with a skir-t, possibly having a serra-ted lower ed~e, which
sinks into the bottom mud and prevents undesired spreading
of macadam, outside of the funnel structure. Such a skirt is
furthermore important when there is a risk of erosion. The
support structure, furthermore, is provided wi-th means for
maintaining the position of the pillar during erection.
The pillar must not necessarily have a circular
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cross-section, but may have a square or otherwise shaped
crOSS-sec-tion. The Eunnel st.ructure may likewise have a shape
differing from -the circular, for instance being polygonal.
The support structure .LS well suited to be used for
the erection of quays or piers, as well as for working plat-
forms and ramps, etc. It may also, for e~ample, be used with
certain bridge struc-tures and with offshore plants.
The present invention will be further illustrtated
by way of the accornpanyi.ng drawings, in which:-
Figure 1 schematically shows a suppor-t s-tructure of
conventional type, used for under-water constructions,
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Figure 2 shows a plan view of the foot of a ~upport struc-
ture according to Filgure 1,
Figure 3 shows a support structure accordin~ to the inven-
tion during erection,
Figure 4 shows a plan view of the foot of a support struc-
ture according to Figure 3, and
Figures 5 - 8 show consecutive steps during the erection of
a pier or a quay-platform, using support struc-
tures according to the invention.
Description of a preferred embodiment
In Figures 1 and 2 numeral 10 denotes the bottom
below a body of water, and 11 denotes the water surface A
support structure 12 of conventional type~ as shown in
Figure 1, presupposes that a level and fully horizontal sub-
stratum 13 of gravel or macadam is formed upon the bottom.
The shape of the support structure may vary depending upon
the depth of the water, and upon the expected load, but it
consists essentially of a pillar 14 and a foot-plate 15,
usually provided with reinforcing ribs 16.
The macadam may be tipped out from a barge, or the
like, and an uneven mound 9 or group of mounds is formed
which must be levelled out by means of a scraper being
dragged forwards and backwards over the location. Due to
the dif`ficulty in locating the substratum exactly in rela_
tion to the desired position of the support structure it
is often necessary to cover an area, which is considerably
bigger than the foot-pla-te 9 and in order to compensate
possible irregularities in the bottom profile and possible
inclination a surplus of macadam must be used. The difficul-
ties in forming the substratum~ and a possible final control
by a diver results in an-expensive foundation.
A support structure according to the invention~ part-
ly filled with macadam, is shown in Figure 3 and comprises
a tubular pillar 20 continued by a reversed funnel structure
21, the ba~e area of which is dimensioned with respect to
the conditions of the bottom and the expectecl load upon
the pillar. T~e ~acadarn is filled by way of the pillar~ and
the funnel structure, directly onto the bottom.
When the pillar with its funnel structure h~s been
brought to the desired position macadam is filled by means
of a supply device 22 in an amount to ensure tha~ the ma-
terial rises partly up into the pillar. This will compen-
sate possible future settlements. The macadam may be sub-
jected to vibrations, so it becomes well compacted and
forms a ho~ogenous mound (cone). This is well centered and
concentrated directly below the pillar, withou-t unnecessary
spreading outside the desired area.
If a fraction of macadam is selected, which in water
has an angle of repose of1 say 45, the supporting struc-
ture is selected with a base angle being somewhat higger
than the angle of repose of macadam, say 48 ~ The base
area of the funnel structure is dimensioned with respect
to the perm:issible specific bottom load. When the macadam
i9 fiiled into th0 funnel structure by way of the pillar9
the f`unnel struc$ure will be 100% filled9 and the internal
envelope face of the funnel structure will rest directly
upon the cone of macadam. The funnel structure will in this
manner be fully supported inside and may be designed as a
simple shell structure. The load upon the pillar will thus,
by way of the funnel structure and the macadam, be trans-
ferred to the bottom surface below the macadam cone.
As the angle of repose of the cone is less than the
base angle of the funnel structure, it is e~ident that the
macadam will adapt itself to the internal surface of the
funnel ~nd to the bottom profile, and to lOO~ will fill the
space between the funnel structure and the bottom.
The support structure ~ay advantageously be posi-
tioned so the base line of the funnel structure remains
slightly abo~e the bottom floor. Possible projections at the
bottom, such as stones or wreckage~ will then not carry some
part of the funnel margin, which could lead to local strains.
A certain amount of macadam will be spread outside the funnel,
but the structure will nevertheless be completely filled.
1~hen the bo-ttom ls soft and muddy, or when there is
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a risk oE erosion, it may be advantageous to provi~e -the ~un-
nel s-tructure 21 wi-th a projecting skir-t 25 along its lower
edge. The skir-t extends vertically and is preferably pro-
vided wi-th a serra-ted edge 26, which easily sinks down in-to
the soft bottom. The skir~ will aid in preventi~g -the macadam
from spreading out.
When high loads, or a risk of buc]cling is at hand,
the pillar may have a considerable diameter. In order to lo-
cate the cone of macadam cen-trally in the funnel struc-ture,
a restriction 23 may be provided within the pillar, just
above the transition thereof into the funnel structure 21.
With under-water constructions the hollow pillar
shall preferably project above the level of the water, i.a.
to facilitate the filling of macadam.
The pillar must not necessarily be a circular tube,
but can have square or some other suitable cross--section. The
pillar can furthermore be flared, i.e. have a downwardly
increasing cross-section.
On certain occasions, i.a. to save macadam, it may
be desirable to fit inserts within the funnel struc-ture, which
makes it possible to distribute the macadam mainly along the
periphery of the funnel structure. It may also be possible
to distribute the macadam in a number of smaller cones arranged
around -the center line.
3Q When the funnel structure and the pillar have been
filled and the macadam has settled, the shell may be injected
with some suitable grou-t.
Support structures of -this type may advantageously
be used for instance with temporary or permanent ~uays, piers,
ramps, or working platforms, etc. t which are carried by a
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a number of "legs". Figures 5--7 show -the inventio~ as used
with a -temporarily erectable pier or ramp adjacen-t -to a quay
30. The pier includes a floating pontoon 31, which in work-
ing position will be carried by means o~ a number of support
struc-tures 32, or legs, of the -type shown in Figure 3. The
legs are mounted in -the pon-toon 31 in any suitable manner so
they may be raised or lowered, for instarlce by means of jack-
up mechanisms 33.
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The pontoon 31 is provided with mooring devices 34,
which in this embodiment will slide along fenders 35 at
the quay 309 and which will retain the pontoon at a distan-
ce from the latter. The pontoon 31 is towed, with the legs
32 raised, to the selected location, and is carefully moored
at the quay. The positions of the legs will in this manner
be exactly defined - see Figure 5. Thereupon the legs are
lowered 3 possibly by means of jack-up mechanisms, so the
funnel structure 2l will rest upon the bottom,or next to
the bottom of the harbour, with possible skirts 25 sinking
into the bottom mud - Figure 3. Movements of the waves and
possible tide water will not act upon the lowered legs, as
the floating pontoon still may move freely up and down along
the pillars, when the jack-up mechanisms have been dis-
engaged. Macadam is then filled into the pillars from the
quay, or from a barge, as the pontoon should not be subjected
to any load while it is still floating - ~igure 70
When the cones 24 o~ macadam below the flmnel struc-
tures have been vibrated and have had time to settle, the
pontoon 31 is successively raised out of the water by means
of the jack up mechanisms 33 to a desired level in relation
to the quay 30 to a horizontal, or inclined position. A
~communica-tion ramp is then e~tended from the quay onto the
pontoon, so vehicles may travel across the pier. The jack~up
mechanisms permit an easy readjustmerlt of the position,
whenever needed. The pontoon 31 is designed in such a mamler
that highest water level will just reach its bottom plating.
There is of course other possibilities of adjus-ting the
height position in relation to the harbour bottom and to the
occasional water level, for example by trimming with ballast
water.
If it becomes necessary to move the pontoon 31 to
some other place 3 the pontoon is lowered until i-t floats,
whereupon the legs 32 are lifted to the position shown in
Figure 5, This is easily accomplished by means of the jack-
up mechanisms~ as the l~gs are not fixed to the bottom.
The remaining mounds of macadam may easily be removed
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by means of dredging, if they are considered as a hinderance
to future traffic at the quay.
The invention may of course also be u~ed with working
platforms or the like, which are located separate from a
quay, and which during the erection are anchored in any
suitable manner for exact positioning of the supporting
legs. One field of use of such platforms is within the off-
shore industry.
The invention may also advantageously be used for
constructions erected upon a bed of fric~ion material above
ground level. The principle is exactly the same. As an
example may be mentioned constructional works in water-soaked
grounds, bogs and the like~ where suppor-t structures are
located in a well or trench and are then filled with macadam.
Such works as sheet-piling, draining of water and casting
of concrete, etc. can then be avoided.
