CA1193457A

CA1193457A - Support structure

Info

Publication number: CA1193457A
Application number: CA000406913A
Authority: CA
Inventors: Klas Heyman
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-01-26
Filing date: 1982-07-08
Publication date: 1985-09-17
Also published as: SE440804B; FR2530699B1; NO820194L; DE3227361A1; SE8100443L; FR2530699A1; GB2123463A; GB2123463B

Abstract

ABSTRACT OF THE DISCLOSURE

A support structure, especially for use in under-water work, comprises a hollow pillar, which downwardly merges into a reversed funnel structure, having a base area selected with respect to the expected load and to local ground con-ditions. The funnel structure and part of the pillar are to be filled with macadam, or other material with internal friction, and the base angle of the funnel structure is slightly larger than the natural angle of repose of the frac-tion of friction material used. After a possible vibration of the macadam the funnel structure will be completely filled, whereby the load upon the pillar will be transferred to the cone of macadam and be distributed over the bottom surface, below the funnel structure. The latter may along its lower edge be provided with a serrated skirt suited to enter into a soft bottom.

Description

~3~
The present invention rela-~es to ~ support structure especi~lly . .
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.

` ~ Qd~

.~

~3~7 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 r~s 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, ;- 3 -5~

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 ~3~
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 6 ~
.~

3~

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.

~- 6a -~3~

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 ~3~

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.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLU-SIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of forming a structure for use at least partly submerged in a body of water and adapted to support a vertical load, wherein the area of said structure resting upon the bottom of said body is a function of the load-carrying capacity of the bottom material, comprising: forming a rigid, hollow pillar, forming a rigid, funnel-shaped struc-ture having a base and a small end, the area of the base being substantially larger than the cross-sectional area of the pillar, attaching one end of said pillar to the small end of said funnel-shaped structure, positioning said funnel-shaped structure and attached pillar in a body of water, with the base setting substantially level on the bottom surface and below the top surface of the body of water, and with the pillar substantially vertical, filling said funnel-shaped structure with a material having internal friction through said hollow pillar, and providing a base angle for said funnel-shaped structure slightly greater than the angle of repose of the friction material so that said funnel-shaped structure is completely filled and the interior surface thereof is entirely supported on said friction material.

2. A method according to claim 1, in which the material is gravel or macadam.

3. A structure adapted to support a vertical load in a body of water, wherein the area of said structure resting upon the bottom of said body is a function of the load-carrying capacity of the bottom material and comprising: an inverted hollow funnel shaped member of rigid material having a base adapted to be set substantially level on a supporting surface and a smaller upper end, a hollow rigid pillar attached at one end to said upper end of said funnel-shaped member, and extend-ing substantially vertically therefrom, the area of said base being substantially larger than the cross-sectional area of said pillar, and a continuous mass of material having internal fric-tion filling said funnel-shaped structure to form a conically shaped support therein and at least partly filling said pillar, said pillar being open at the top to allow said material to be filled therethrough, the base angle of said funnel-shaped member being larger than the angle of repose of the material so that the funnel-shaped member is completely filled and the interior surface thereof is entirely supported on said material.

4. The structure according to claim 2, wherein the section where said pillar is attached to said funnel-shaped member forms a transition, and said hollow pillar adjacent to the transition is provided with reduced diameter restric-tion having a centrally located passage therethrough for pass-age of said material to centre the conical mass thereof within said funnel-shaped member.

5. A method according to claim 3 or 4, in which the material is gravel or macadam.