A METHOD FOR PERFORMING UNDERWATER CASTING OF CONCRETE STRUCTURES,AND AN APPARATUS FOR CARRYING OUT THE METHOD

Abstract: Method and apparatus for carrying out under water casting of concrete structures by utilization of slip form equipment. The slip form unit (19, 20, 22, 25) is suspended in stays (27) supported in hoisting means (30) mounted on a support construction (2) in above water position, is being sunk down onto the casting site on the sea bottom (50), possibly subsequent to that the sea bottom has been levelled and prepared. One or more supply conveyors, such as tubes (46), are devised from suspension means (45) on the support construction in order to extend down into the slip form (20). The casting tubes are being filled with ready poured concrete. The slip form is hoisted upwards in correspondence with the hardening speed of the poured concrete, simultaneously as suitable quantity of poured concrete mass is supplied to the casting site through the casting tubes. The slip form equipment is suspended in hoisting means mounted on the support construction in such fashion that one can carry out directional guiding and adjustment of the position of the slip form during the casting operation.

Description: A method for performing -underwater casting of concrete structures, and an apparatus for carrying out the method. The present invention relates generally to a method for performing underwater casting of concrete, more particularly to - a method enabling utilization of slip forms for such concrete casting works, and the invention relates further to various apparatus for carrying out the method. Underwater casting of concrete structures, such as foundations for peers, bridges, etc. are with conventional technique carried out with stationary shuttering which is fixed to the sea bottom or to a ready-made portion of the structure. Initially is usually cast-a foundation bed on the sea bottom, subsequent to a suitable levelling thereof, whereafter the shuttering is mounted onto the foundation bed. In this fashion is carried out underwater casting of solid foundations such as columns and the like, with a shuttering which is exposed to external concrete pressure only, as well as wall structures and the like, whereby the shuttering must be formed"for sustaining bilateral concrete pressures. Required reinforcements of the concrete structures must usually take place, at least partly, by the help of diving operators. Poured concrete is usually brought down to the working location by means of so-called casting tubes conveying the poured concrete from a suitable source in position above water down into the shuttering. Particularly in connection with the casting of structures requiring bilateral concrete pressures on the shuttering,the reinforcment works fall costly and cumbersome because the reinforcing elements, such as steel rods or mats, must be positioned downwards between cross-bracing elements which are interconnecting the shuttering elements. Frequently it is difficult to avoid that the reinforcing elements subsequent to positioning are displaced, for instance onto the shuttering boards, having into effect that the reinforcing elements are subsequently exposed to the seawater with heavy corrosion thereof in result. It would therefore be of great importance if a better and more dependable method for reinforcing of such underwater concrete works could be developed. The principal object of the present invention is to provide a more effective method for carrying out casting of concrete structures below water. A further object for the invention is to provide better means and apparatus for carrying out various types of under¬ water concrete works. A particular object of the invention is to provide a method and apparatus which can make it easier and with less danger for the workers to carry out reinforcing of under¬ water concrete works. For carrying out concrete structures ashore it is today conventional to utilize the slip forming principle i.e. utilizing a slip form with a limited length' or height and which are moved continuously in the casting direction parallel with the pouring and hardening of the supplied concrete. The slip forming equipment is usually moved as a unit which is supported and raised on so-called climbing steel elements which are located and in some cases embedded in the concrete structure. The climbing steels may consist of reinforcement steel rods or rods which are embedded in the concrete, or alternatively rods which are positioned loosely in a piping which are embedded in the concrete. The reinforcing of concrete structures in connection with slip forming may fall comparatively cumbersome, particularly if the work concerns slip forms with bilateral concrete pressure, that is concrete walls or the like, since then one will have a number of cross- bracers above the casting between the slip form walls on either side. ' These cross-bracers interconnect and position the slip form boards, simultansously as they serve as supporting elements for jack-up means which stand in engagemen with the steel elements positioned in the concrete work. The reinforcing must then under the concrete pouring be positioned one after the other down into the concrete as poured between and below the superimposed cross-bracers. Vertically extendin reinforcing falls comparatively simple while horizontally extending reinforcments and the positioning of mats may be difficult and interconnection of the reinforcement elements must frequently be carried out in situ. Underwater casting of concrete by means of slip forming is, as far as is known, not hitherto carried out, at least not in full normal scale. Several reasons may add to this O PI WIPO Firstly, the development of underwater slip forming equipment requires the. existance of equipment which is operable under water. Secondly, the reinforcement of underwater concrete works in connection with slip forming may of couse be very difficult. The reinforcing of underwater concrete works must as mentioned most usually be carried out by means of diving operators which in itself is expensive and dangerous, particularly due to very poor sight in the water due to water contamination in the vicinity of the working site. The casting of concrete structures under water is proposed in British patent specification No. 1 315 210. In this patent is shown a type of slip forming equipment with bilateral concrete pressure for the casting of hollow columns and which equipment is supported by a surface vessel by means of cables or the like. The lifting of the slip forming shall take place by means of special buoyancy tanks which are mounted between the shuttering walls and which shall provide suitable buoyancy force by supplying a controlled quantity of compressed air. As far as the applicants know, the method in accordance with this patent has hitherto not been carried out. The method seems to imply several substantial short¬ comings. Firstly, it is clear that the slip forming equipment may be subjected to incidental vertical movement in correspondence with the vertical movements of the floating vessel. Furthermore, it seems difficult to ensure that the slip forming equipments are given sufficiently secure and stable rising movements by means of the buoyancy equipment shown. The method in accordance with the present invention is similarly based on the use of slip forming equipment, and the method is generally characterized in that the slip forms during the casting operation is supported and hoisted upwards by means of suspension cables or hangers, such as rods or cables which are connected to hoisting means mounted on a stable and stationary supporting structure positioned above the water surface, simultaneously as poured concrete in known fashion is supplied to the casting side through casting tubes or the like in suitable quantities and more or less continuously in correspondence with the rising of the slip forming unit. The slip forming unit is in the preferred embodiment ' provided as a unit which is supported by an overhanging rigid horizontally extending structure which again is suspended in at least three vertical hangers or stays which each are connected to a separate power jack or the like. Thereby the exact position of the slip form unit will be, at any time, subject to full control, • because in lateral direction the slip forming unit will be kept immovable by means of the below positioned ardent concrete still in contact with the slip form and vertically, the slip form uni may not only be raised, but may be guided and directionally controlled by carrying out individual adjustment by one or more of the hangers by means of the raising jacks. This method makes it possible to carry out a far more effective underwater casting of concrete structure. Further more, it will make it far more simple to carry out reinforce¬ ment of-the concrete works, because the slip form unit may in upward direction remain more or less open without obstructions, disregarding some very few horizontally extending elements which, however, may be positioned well above the casting or pouring site,and in some cases hori¬ zontally extending supporting elements may be entirely avoide The supporting construction in a position above the sea surface for supporting the slip form equipment may be of various type depending upon the kind of work involved, the sea depth, etc. The supporting construction may thus consist of a working platform of the jack-up type with legs, a cantilevered structure mounted onto an existing foundation, or possibly also to a floating vessel, then preferably a vessel of semi-submersible type. Preferred embodiments of the invention shall now be described with reference to the accompanying drawings, wherein: Figures 1 and 2 are a schematic plan view and elevation view, respectively, showing a construction for carrying out the method, and Figure 2 is showing the construction with the equipment in position for initiating the casting work. Figures 2a to 2e are simplified detail views illustrating the various steps in the prosedure to carry out the casting work. Figures 3a to 3c are detail views which likewise Figures 2a to 2e illustrate a method for protecting freshly poured concrete against erosion. Figures 4 and 5 show a schematic plan.view and elevational view, respectively, of a slip form equipment in accordance with the invention which shuttering is made for bilateral concrete pressure. Figure 6 is an elevational view of another embodiment of the supporting construction including a cantilevered support from an existing foundation. The casting scaffolding or frame comprises a horizontal support or platform with a frame 2, in the shown embodiment comprising two side by side parallelly extending hollow beams 4,6, made as buoyancy elements. These beams are mutually connected with transverse hollow beams 8,10. This platform structure is provided with four jackable supporting legs 12, 14,16,18^ enabling same to be moved vertically down for support on the sea bottom for subsequent lifting of the platform structure to a position above the water surface straight above the working site. On the platform is installed the casting equipment, and the equipment for supporting and raising the slip form unit which in the shown embodiment consists of a square slip form frame 19 for singular or one-sided, internal concrete pressure (solid column) and which on the inside is furnished with the slip form boards 25, which are positioned with a downward outward slip to facilitate the raising of the form work and prevent injury of the concrete surface. The slip form unit is suspended on a rigid truss frame 22 which in the shown embodiment consists of two couples of mutually crossing steel beam sections 23a and 23b, respectively. Through this design is aimed at obtaining large span widths between the sections 23 in the frame and plenty of height below the frame, that is the height h down to the casting site in order to facilitate the equipment for easy positioning of necessary reinforcements in the concrete, such as steel rods or steel mats. The entire slip form unit is at anchoring points 24 suspended in the number of vertical stays, in the shown embodiment comprising four pipe strings 27a-d, each OMPI preferably consisting of interthreaded sections. On the platform 2 these suspension stays are firmly engaged by so- called climbing jacks 30a-d (hydraulic/pneumatiσ/electrical) which are operationally connected to a not shown control system, such that the stays can be raised at equal rate of speed or/and different speed in order to allow for individual adjustment in one or more of the stay suspension. On the platform 2 is further installed a complete castin gear 36. This gear comprises a crane boom 38 with a travelli winch crane 40 to carry a concrete • contained 42 for delivery of ready-made poured concrete to a number of hoppers 44a, ,c, d,e,f, which are suspended in trolleys 45 from a transverse beam 47. Each of thehoppers carries a downwardly pointing so-called casting tube or hose 46a-f, respectively, which lead directly down to the casting site in the slip form unit The above described aggregate or plant composes the main elements " in an embodiment for an apparatus in order to carry out the method in accordance with the invention. The technic equipment involved can thus be in per se conventional and should not be necessary to describe in detail. Thus, on the working platform 2 can be arranged a mixing plant for making ready-made poured concrete. Furthermore, the casting tubes or hoses 46a-f are suitably supplied in detachable sections in order to adjust the length of these tubes to the need at any stage of the casting operation. Figure 2 is illustrating the entire aggregate in working position in order to initiate the casting job utilizing the method in accordance with the invention. The platform etc. is in advance floated out to the working site. Under the floating operation the slip form equipment 20 is raised up to a position between the hollow beams 8 and 10. Furthermore the casting tubes 46 are obviously raised up. On the working site the jack-up legs 12,14,16,18, are by means of the jack system moved down to resting locations 31,31 on the sea botto circumferentially around the casting site, and the platform 2 has been raised up to the above water position as shown. Of other preparatory works can be mentioned that the sea bottom on the casting site is usually prepared, for instance OMPI levelled, and if necessary, a special bottom foundation of concrete is made, in such case preferably including a number of free-standing upwardly pointing reinforcing steel rods, firmly embedded into the bottom concrete foundation. There¬ after the slip form unit has been sunk ' down onto the casting site. During this operation further sections of suspension stays are supplied in accordance with the need. The slip form unit is in this fashion sunk down and positioned on the casting site. Simultaneously or subsequently the required number of casting tubes are sunk down and positioned as shown. The casting tubes can consist of rigid tubing or in part or wholly of flexible housing, for instance reinforced plastic housing. The carrying out of the casting work shall now be described with reference to the detail views, Figures 2a-e, illustrating various stages during the casting operation. The slip form boards 25 are initially resting on the sea bottom or onto the foundation 50 and may be firmly positioned utili¬ zing the upstanding reinforcing rods 52. This initial position is shown in Figure 2 (and 3a) . The casting tubes are being filled with poured concrete from the hoppers on the platform deck 2. The poured concrete will, due to its gravity, fill out the tubing and initially flow out of the bottom openings of the tubes and will thereby soon fill up the surrounding slip form space until the pressure around the tubing openings equalizes the present static pressure in the tubings, cf. Figure 2b. The casting tubes may, if desired, in the bottom section be provided with remotely controlled check valves 33, among other things to prevent incidental, uncontrolled flow- out of poured concrete. It is now referred to Figure 3c, illustrating a second stage during the casting procedure. At this stage the casting tubing 46 has been lifted up to a certain level corresponding approximately to half of the height of the form boards 25. The poured concrete in the casting tubing will in this position anew flow out until the described auto¬ matic or internal locking takes place due to the pressure equalization. Reinforcing of the casting preferably takes place at intervals or rests in the supply of concrete. A supply of reinforcing rods or the like can be placed in a rack O PI 53 mounted on the supporting beams 23, and these may also serve as working platform for divers during the work for positioning reinforcement 54 in the ' concrete as poured. When the concrete as poured has solidified or hardened to a sufficient degree one can initiate the raising of the slip unit via the suspension stays by means of the jacks 30 posi¬ tioned on the platform 2. Partly to prevent leakages of poured concrete below the bottom edge of the slip form boards, and partly to protect the progressively exposed side surface of the cast concrete work, one has in accordance with the invention along the botto edge of the slip form boards positioned downwardly pointing skirt means. As such protecting skirt means may be used boards made of wood or steel and they consist preferably of flexible material such as plastic sheeting or the like and the skirts are positioned as downwardly pointing extensions of the form plate boards. The required height of such skirt means will depend upon several factors, such as the hardening speed of the concrete, the flow conditions in the water, etc. In Figures 3a-c is illustrated an embodiment for a such skirt means 55 wherein is used flexible curtains of plastic sheeting provided in the shape of one or more rolls 56. The top edge of this sheeting is attached to the bottom edge of the form boards 25. In correspondence with the raising of the slip form the curtain will roll off from the roll and position itself along the outside of the concrete as cast as is illu¬ strated in Figures 3b and 3c. When the entire skirt or curtain has been rolled out one may at the lower edge of the curtain position a circumferentially running clamping frame or the like such as indicated at the reference number 58. Continued casting of the shown solid column may now take place more or less continuously, since the slip form unit is raised in correspondence with the actual solidifying speed or hardening of the concrete as poured, simultaneously as poured concrete more or less continuously is supplied to the slip form through the casting tubes 46. It is important to be able to supply poured concrete, and to raise the casting tubes as quickly as possible and also continuously in order to avoid danger for that the casting pipes are being more or less permanently embedded into the concrete as poured in the slip form. The same counts for the slip form unit, even though the slip form boards are positioned with a slip. Interruptions in the raising thereof may result in that the slip form boards adhere to the concrete mass and have in result a possibility of injury of the equipment and the casting work and other problems. In the method in accordance with the invention one may however utilize relatively large or high slip form boards normally without any risk for that the boards adhere to the solidifying concrete surface. In regard the skirt or curtains, these are suitably given substantially the same height as the slip form boards. Other¬ wise, the vertical dimension of the slip form boards and the skirt will depend upon the dimensions of the casting work in question and other conditions. It will be understood that the method in accordance with the invention can be carried out with various types of slip forms and various types of casting equipment, etc. The Figures 4 and 5 show a plan view and an elevation, respectively, illustrating schematically a slip form unit for carrying out bilateral concrete casting. The slip form comprises an internal and an external support structure 60,62 to which is attached the slip form boards in the same fashion as shown in Figures 1 and 2. The slip form unit is here suspended on two horizontal support beams 64 and 66, and which are suitably further suspended in four vertical stays 68 in anchoring points 70. Also in this embodiment it will likewise be suitable to utilize a protection skirt or curtain (not shown) on the outside of the casting, but not on the inside. A suitable number of casting tubes 72,72, etc. are directed down between the slip form walls. A slip form unit with bilateral concrete pressure as shown can without particular difficulties be designed such that it has full opening in direction upwards, disregarding the shown port beams, and the positioning of reinforcements in the casting during the pouring of the concrete will fall relatively simple. Figure 6 is showing an elevational view of an alternativ set-up for carrying out the ' metho ' d, wherein the slip form uni and the lifting jacks 82 which otherwise can be similar to the equipment shown in Figures 1 and 2, are supported on a cantilever support 84 with a support foundation 86 which is anchored to an existing rigid foundation structure 88. The casting method otherwise will be identical to the one already described. When the casting work is completed up to height o level with the shown existing rigid foundation 88, the new foundation column or object can serve as foundation for a next casting work, etc.

Claims: P a t e n t C l a i m s 1. A method for carrying out underwater casting of concrete structures utilizing slip form equipment, c h a r a c t e r i z e d by suspension of the slip form unit in stays supported by hoisting means mounted on a support structure in above water position, the slip form being sunk • down onto the casting site on the sea bottom, possibly sub¬ sequent to that the sea bottom is levelled and prepared, positioning of one or more supply conveyors, such as tubes, extending from suspension means on the support structure and down into the slip form, for the supply of poured concrete, filling of the casting tubes with ready-made poured concrete, controlled hoisting of the slip form unit in correspondence with the hardening speed of the concrete, simultaneously as suitable quantities of ready-made poured concrete are supplied to the casting site through the casting tubes. 2. A method in accordance with claim 1, c h a r a c t e r i z e d therein that the slip form as well as the casting tubes are being raised in correspondence with the supply and the hardening of the concrete, simultaneously as suitable poured concrete continuously is supplied to the casting site by means of the casting tubes. 3. A method in accordance with claims 1 and/or 2, c h a r a c t e r i z e d therein that the slip form is suspended in a number of suspension stays which are indivi¬ dually suspended in hoisting means on the support structure in order to control and possibly adjust the position of the slip form during the casting. 4. A method in accordance with any of preceding claims, c h a r a c t e r i z e d therein that the supply conveyors for concrete, such as casting tubes, during the casting work are being maintained full of ready-made poured concrete from a storage thereof on the support structure and in that the concrete is discharged on the casting site in the slip form by upwardly hoisting of the casting tubes in a suitable fashion in order to effect the discharge of the concrete mass in the slip form, the discharge speed of the concrete from O PI Λ. WIPO . * the mouth openings of the tubes taking place in dependence on the degree of submersal of the pipe opening in the concrete mass in the form. 5. An apparatus for carrying out the method in accordance with one or more of the preceding claims, c h a r a c t e r i z e d therein that the support structure for the slip form and the casting unit comprise a platform¬ like frame construction devised with three or more individuall jackable adjustable downwardly pointing support legs designed to rest onto the sea bottom circumferentially around the casting site, such that said frame construction can be raised on the casting site up to position above the water level. 6. An apparatus in accordance with- claim 5, c h a r a c t e r i z e d therein that said frame constructio includes buoyant bodies such as a number of hollow box beams such that the entire support structure including all equipment can be floated out to the casting site. 7. An apparatus in accordance with claim 6, c h a r a c t e r i z e d therein that the frame construction is designed with an open and free center area for reception of the slip form unit in suspended position and that above this free area is positioned transverse overhead beams for positioning the hoisting means for the suspension stays, the casting equipment, the casting tubes, etc. 8. An apparatus in accordance with claims 5-7, c h a r a c t e r i z e d therein that the casting tubes uppermost are connected to supply hoppers which further are hoistably supported onto the transverse beams. 9. An apparatus in accordance with any of claims 6-8, c h a r a c t e r i z e d therein that said support- and suspension stays for the slip form unit consist of rigid elements, preferably interthreadable sections of rods or pipes 10. An apparatus in order to carry out the method in accordance with any of preceding claims, 1 - 4, c h a r a c t e r i z e d in that the support structure comprises a cantilevered structure with an inside part designe to be supported on an existing foundation or the like, and an outside cantilevered part which supports the casting equipment O PI including suspension means for th slip form unit positioned straight above the casting site. . 11. An apparatus for carrying out the method in accordance with any of claims 1-4, c h a r a c t e r i z e d in that the support structure consists of a semi-submersible floating vessel or platform. 12. An apparatus in accordance with any of preceding claims 5-11, for the casting with a slip form for unitary or one¬ sided concrete pressure, c h a r a c t e r i z e d therein that the slip form unit consists of a rigid open frame to the inside of which are attached the slip form boards, and a unit of overhead transverse support beams provided with fixing points for the suspension stays. 13. An apparatus for carrying out the method in accordance with claims 1-4, for casting utilizing slip forms for bilateral concrete pressure, c h a r a c t e r i z e d therein that the slip form unit consists of two box-shaped open frames provided with the slip form boards on opposed sides in the lower part of the frame, which frames are fixed to the superimposed overhead transverse beams in suitable position relative to the anchoring points for the suspension stays. 14. An apparatus in accordance with claims 12 and/or 13, c h a r a c t e r i z e d therein that along the bottom edge of the slip form board are arranged downwardly pointing plates or skirts for protecting newly poured concrete against washing and erosion. 15. An apparatus in accordance with claim 14, c h a r a c t e r i z e d therein that said protection skirts are flexible and for instance consist of plastic sheeting.. 16. An apparatus in accordance with claim 15, c h a r a c t e r i z e d therein that said curtain initially, when the casting shall be initiated, is available as a roll in wound up fashion and positioned outside the bottom edge of the slip form and is arranged to wind off from the roll during the raising of the slip form and in position against the newly cast concrete surface. 17. An apparatus in accordance with claims 15 and/or 16, c h a r a c t e r i z e d by a circumferential yoke or the like to be engaged with the lowermost part of the curtain when said is completely wound out. "

Inventors: OPEDAL T
Applicants: OPEDAL T, SELMER AS ING F, INGENIOR SELMER AS F
Application year: 1980
Main classification: E04G11
IPC codes: E02D15