CA2091938C - Method of manufacturing a hollow self-supporting concrete structure, means for performing said method and structures obtained by means of the method - Google Patents

Abstract

The invention relates to a method and means for manufacturing freely supported dome or tunnel-shaped structures by means of spraying a particular mortar with micro silica onto an inflated bladder (2) or sheet with or without a primarily applied layer (15) of foam and with or without reinforcing means (23, 24, 28) in particular for manufacturing a tunnel-shaped span (21) for a highway or railway portion.

Description

Method of manufacturing a hollow self supporting concrete structure, means for p~lrul~ g said method and structures obtained by means of the method.
The present invention relates to a method of m~ml~turing a three ~limen~ional hollaw self-~uppo~ lg concrete structure of subst~nti~lly tunnel-shaped configuration by 5 infl~tin~ an airtight space formed by an airtight ~exible sheet having its edges secured to a foundation or base and comprising a tunnel wall portion and end walls, which sheet, after having obtained its proper inflated shape is stiffened by ~ ying onto it a hardening m~t~ori~l, such as mortar or concrete whilst the tunnel-shape under the plt;S~ure of the inflation is stabilized by sheet supporting ribs or trusses at spaced apart locations in planes 10 which subst~nti~lly extend in a direction transverse to the longit,udin~l axis of the tunnel which spraying of the hardening m~t~,ri~l primarily is performed at the location of the ribs or trusses after which the spaces in between said ribs or trusses are filled by spraying the hardening m~t~,ri~l upon the l~ inillg sheet portions between the ribs or trusses.
Such a method is known from US-A-3 139 464. According to said known method a 15 tunnel-shaped structure can be manufactured by primarily erecting upon the base a plurality of spaced apart prefabricated metal trusses in the shape of arches which give support to the afterwards inflated sheet which by the overpressure inside the sheet is pressed against the inner side of said trusses and bulges uul~drdly in the space between said trusses. According to said prior art it also is possible to provide the trusses at the inner side of the sheet in 20 which case however additional measures are necessary to connect the sheet with the trusses and to ensure the outwardly curved shape between the trusses. After the erection of the trusses and the inflation of the sheet mortar is applied by pouring or spraying, primarily at the location of the said trusses which then are embedded within the mortar and after hardening of said mortar, mortar is applied over the Oul~d~dly bulging or lmdlll~ting shape 25 of the sheet between the respective trusses. This spraying or pouring takes place from the outer side upon the outer side of the trusses and sheet.
Said trusses are necessary to obtain sufficient stability because if mortar would be applied locally upon the inflated sheet a der.,lllla~ion would t~ke place under the influence of gravity forces which would prevent obtaining of the proper tunnel shape. The outwardly 30 bulging parts provide for a bending moment of resi~t~nce and in some cases the shape of said outwardly bulging parts is not only a result of the pressure inside the sheet but is also under control of longit~l(lin~lly extending tie cables 64 to obtain re,si~t~nce against the spreading loads during the application of the mortar over said uu~ dly bulging or arching parts between the trusses.

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- 2 ~ 2 0 9 19 38 By means of said known method an excellent and strong tunnel structure can be m~nuf~r,tured but said method is very compli~t~ and accordingly expensive.
The purpose of the invention is to simplify the m~nuf~ctllring of a tunnel-shaped structure and according to the invention this purpose is achieved in that the hardening 5 m~t~,ri~l is a mortar with a micro-silica content such that the freshly sprayed concrete in its still plastic stage has form stability, and that after the inflation of the sheet the ribs or trusses are formed by spraying mortar, in the shape of ribs, against the inner side of the sheet, so that the ribs or trusses support the sheet after hardening of the mortar.
Accordingly the invention uses a sheet or sheet for the tunnel-shaped portion which 10 prior to the ~tt~,hment to the foundation is a flat sheet preferably composed of flat strips welded together at overlapping edges which sheet after ~tt~t~,hm~,nt to the base and closing the outer ends and inflation forms a straight smooth tube which however lacks stability. Said stability is obtained by man~ ,tllring the spaced apart ribs or trusses after the inflation with the aid of a mortar which due to its silica content obtains imm~ t~,ly sufflcient stability to 15 form said ribs against the inner side of the inflated sheet but without exerting load of any ol~lce upon said sheet. After the m~nuf~cturing of said ribs and the hardening thereof the ~ ining areas are covered by spraying said mortar but now the ribs give support to the inflated sheet. A mortar composition conl;1ining a micro-silica is known in many varieties.
Usually said compositions are not suitable for spraying because the strong cohesive character 20 of the ~ ul~ opposes the transportation towards the spray nozzle. From DE-A-39 41 152 a method and apparatus is known however by means of which spraying becomes possible due to the fact that a primarily prepared badge of mortar llli~LtUl~ under air pressure is fed towards an injector together with transporting air supply. The injector is close to the tank in which the mortar mi~lu~ badge is present so that the risk that the llli~lul~ sticks within the 25 conduit due to the strong cohesive plo~?ellies has been avoided. Downstream the injector air flows which air is mixed with the finally divided mortar. By using said known method and device it is possible to spray mortar which due to the immediately obtainable form stability allows the creation of objects of the ribs or trusses mentioned above.
The spraying takes place on the inner side and most preferably after the application of 30 a synthetic foam layer because a foam layer of for instance polyurethane does adhere to the m~teri~l of the sheet and provides for better adherence of the mortar than in case a direct application takes place. Spraying upon the inner side against a synthetic foam layer which has been applied first is for instance known from EP-A-O 357 151 which relates to the manul~tllring of dome-shaped structures which means a structure having a vertical axis of symmetry in which case different measures are necessary to take care of the influence of gravity forces. ~lth a horizontal axis the situation is different.
By making use of simple strips for the inflatable sheet and by using special mortar which can be sprayed and by m~nuf~ctl-r1ng the ribs or trusses after inflation an extremely 5 simple method is obtained.
It is prcl~ed that prior to the m~nuf~cturing of the said ribs a lower wall is formed upon the base and against the lower side wall of the inflated sheet. This illl~lVVtiS the initial stability in particular during the subsequent m~mlf~cturing of the ribs.
The use of reinforcing bars itself is known for instance from US-A-3 139 464 and10 from EP-A-0 357 151. ~lthin the scope of primarily m~mlf~cturing the ribs it is however advantageous to place reinforcing bars for the ribs at the locations where the ribs have to be m~mlf~t tllred and to place said bars between le l.~old,ily mounted side casing plates which allows a proper configuration of the sides of the ribs during the spraying and which are removed prior to the spraying of the final layer or layers of the ribs and of the areas between 15 the ribs which subsequently have to be coated.
The mortar with the micro-silica content covers and adheres in an excellent manner behind and around the reinforcing rods.
Apart from the micro-silica said mortar can have any type of additional m~t~ri~l~
added to the cement such as hardening accelerators, fly ash, synthetic porcelain, quartz, 20 sand, quartzite, tress, bauxite and acceptable synthetic m~t~ri~l~ as well as all kinds of fibre reinforcçm~nt~ made from resins, glass, steel, carbon or aramide.
Said fibre reinforcements are of particular use if spl~yiilg takes place without the use of reinforcing rods as well may be the case with spraying on the outerside of the sheet or in the m~mlf~cturing of structures of relatively small siæ.
~lth the method according to the invention a great variety of structures by means of inflation and spraying can be made.
The areas belwæn the ribs may be completely filled but of course it is possible to leave part of the areas between said ribs uncovered so that openings remain in which the sheet more or less allows the entrance of light or at which the sheet is removed for ventil~tion purposes. A plt;rt;lled application is the manufacturing of a tunnel-shaped structure which spans a highway or railway track portion. This may be of illl~l~lce in densely populated areas where the so called "sound-walls" are in~lfflcient to keep trafflc sound away from the living qua~ of the population.
Said structures may even be covered ~~ uds with earth.

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The present invention is, however, not limited to this form of application. The tunnel-shaped structures manufactured according to the invention can also be used as inner coating of a tunnel drilled through rock.
The invention now will be further el~ d~tPd with reference to the dl~wings.
Figure 1 is a side view of an inflated sheet to be used in the method according to the invention.
Figure 2 is a cross section according to the line II-II of figure 1.
Figure 3 is a cross section according to the line III-III of figure 1.
Figure 4 shows in a perspective view a section of the structure to be m~m~ tured10 according to the invention.
Figures 5a to 5f incl. disclose a number of subse~uent phrases in the manufacturing of the structure as shown in figure 4 or 8.
Figure 6 is a cross section through a rib at a level ~dj~tPnt to the base, e.g. at the level of the arrow VI in figure 5d.
Figure 7 is a cross section through a rib, e.g. at the level of the arrow VII in figure Se.
Figure 8 discloses sçllem~ti~lly the supply and discharge of m~tPri~l during them~mlf~cturing process.
Figure 9 is a top view of one embodiment of the structure obtained by applying the method according to the invention.
Figure 10 is another top view of the structure obtained by obtaining the method according to the invention.
Figure 11 is a cross section through a finished structure.
Figure 12 is a cross section through another embodiment of the finished structure.
Figures 1 and 4 show a base structure 1 made from concrete either prefabricated or m~nul~rtmed at the site.
A plastic sheet having the general reference 2 is secured to said base in an airtight m~nner Said plastic sheet 2 is composed of a plurality of parallel webs 3, which as shown in 30 figure 3 overlap each other and are welded with their overlapping edges upon WO 93/02264 PCr/NL91/00130 each other by means of high trequency to torm welding seam 4. The ~nnection at said over.,rp.. ,9 edges is a pe",.anent oonnection.
At the outer ends end sheets 6 and 7 respecti~ely are o~nnected in a detachably ",anner to the oul~llllGal edges 8 and 9 respecb~ely of the i-" e,~nnected 5 webs 3 by cl~"plng said outermost edges between strips 10 and 11 respecti~ely which extend in planes parallel to the surfaoe of ~e webs. Said connection by means of bolts and nuts 12 and 13 ,esp~cti~ely is detachable so that said end sheets 6 end 7 respecti.~ely can be removed. This removal is nscessAry when the required length of the tunnel-shaped structure is r,n;shed and/or an extension in one or the other dir~lion is 1 0 desirable.
The end sheets 6 and 7 are also connected to a base part 14 and 15 respectively which are removably oonn6cted with the base 1. r,eferably said parts 6 and 7 have the shape of one quarter of a sphere in the inflated oondition.
After i"na~ion in a well known "~nner the coating of mortar can be applied.
In most cases a foam layer will be applied first.
Figure Sa shows in cross section the inflated sheet.
Figure Sb shows the snuation after the ~rFI e~tion of a foam layer 15.
Figure Sc shows as well as figure 4 that pri",uil~r lower wall F~,lions 16 and 17 respectively are made by spraying or by pouring conclete betw~en the inner side of 20 the sheet wnh or without coating wnh foam and a lo",po,ary casing (not shown).
After the manufacturing of said wall po,tions 16 and 17 ribs 18,19 20 and so one are manufactured as shown in figure 5d.
As next step re;nforcing rods 19 are plaoed b~t~een the ribs as shown in figure 5e and finally monar is sprayed h ~ areas remaining between the ribs so that 25 the final shape shown in figure 5f is obtained in which the self s-,ppo,ling is substantially formed by rT~ar or conc,ete 21.
Figure 4 dis~hses in perspecti~e the bwer wall pGIlionâ 16 and 17 the ribs 18 to 20 etc. and the rcin~orcing netv~ork 22 t~t~e~n said ribs.
The ro;nf~,cing netv~ork betv,een t~e ribs is su~slantially the same as the 30 rein~orcil)g network used in accordanoe with the above cited prior art.
In the manufacturing of the ribs 18-20 which ribs give initial strength to the structure ~ ~v.;ng wide spans it may be desi, ~le to use reinfor..~" ents as weli.
Although the mortar may contain any kind of lo;nforc;ng fibre the traditional rein~orcing rods are preferred to take up the loads in particular bending loads to which 35 the entire structure is and will be suhjected Figure 6 discloses that r~in~,cil)g rods 23 are plaoed parallel to the contour of the rib to be manufactured in a space which is delimited by te",porarily casing plates 22 and 25 re:spe.;li~ely. After the mounting ot said rods 25 and the casing plates 24 and 25 mortar is sprayed in the space limited in a lateral direction by said plates 24 and 25 until the reinforc;ng rods are covered. Thereafter the plates 24 and 25 are removed and 5 a final layer 26 is applied either on the ribs separately or logetl,er with the spraying of ~e areas such as 27 beh~een the ribs.
Figure 7 discloses the same situation but now after the ar)pli~tion of a foam byer 15 upon the outer sheet 2.
Prior to the ~plic~tion of the final layer 26 addilional rein~orcing rods like 28 10 can be applied.
Figure 8 discloses one way of manufacturing the tunnel-shaped structure shown in the preoeding figures by using an inf~ le sheet 2 having air locks 29 and 30 respectively of a size such that a truck 31 can enter it. Said truck can enter at one end deliver its material inside the inflated part and leave it through the other air lock 30.
Sinoe an extension of the structure shown in figure 1 easily can be made as indi~ed with the interrupted lines 4 l large lengths can be manufactured.
Figure 9 discloses an e",bodi",ent which may have the cross section shown in figure 11 or 12 and which in the upper part of the tunnel-shaped structure has uncoated areas 32 between the ribs 18 19 etc. and at which the sheet 2 may have been 20 removed.
As shown in figure 11 a highway sh elded in this way trom its environment can have light and ~,e"tila~ion openings provided by said uncoated areas 32 and it can be or not be incG,~oraled in the landscape by the additional ~plic~ion of earth 33.
Instead of placing the ribs parallel to each other and perpend;cular to the 25 longitudinal axis said ribs can be plaoed at angles as shown in figure 10 in which each pair of ribs 34, 35 intersects at the top at a sharp angle. Also here open spaces 36 and 37 respec~ ely can be created.

Claims (6)

WE CLAIM:

1. Method of manufacturing a three dimensional hollow self-supporting concrete structure (20) of substantially tunnel-shaped configuration by inflating an airtight space formed by an airtight flexible sheet (2) having its edges secured to a foundation or base (1) and comprising a tunnel wall portion and end walls (6, 7) which sheet (2), after having obtained its proper inflated shape is stiffened by spraying onto it a hardening material, such as mortar or concrete whilst the tunnel-shape under the pressure of the inflation is stabilized by sheet supporting ribs or trusses (18, 19, 20) at spaced apart locations in planes which substantially extend in a direction transverse to the longitudinal axis of the tunnel which spraying of the hardening material primarily is performed at the location of the ribs or trusses (18, 19, 20) after which the spaces (22) in between said ribs or trusses (18, 19, 20) are filled by spraying the hardening material upon the remaining sheet portions (22) between the ribs or trusses (18, 19, 20), characterized in that the hardening material is a mortar with a micro-silica content such that the freshly sprayed concrete in its still plastic stage has form stability, and in that after the inflation of the sheet the ribs or trusses (18, 19, 20) are formed by spraying mortar, in the shape of ribs (18, 19, 20), against the inner side of the sheet, so that the ribs or trusses (18, 19, 20) support the sheet (2) after hardening of the mortar.

2. Method as claimed in claim 1, characterized in that first a lower wall (16, 17) is formed upon the base (1) and against the lower side wall of the inflated sheet (2) before the said ribs (18, 19, 20) are made.

3. Method as claimed in claim 1 or 2, wherein the ribs (18, 19, 20) are made in parallel vertical planes which extend perpendicular to the axis of the tunnel.

4. Method as claimed in claim 1 or 2, wherein the ribs (34, 35) are made in vertical planes of which at least two planes intersect each other at a sharp angle.

5. Method as claimed in claim 1 or 2, in which reinforcing bars are arranged prior to the spraying of the mortar, characterized in that prior to the spraying of the ribs (18, 19, 20) the reinforcing bars (23) for the ribs are placed between temporarily mounted side casing plates (24, 25) to properly define the sides of the ribs, which plates (24, 25) are removed prior to the spraying of the final layer or layers (26) of the ribs (18, 19, 20) and prior to the spraying of the areas in between the ribs.

6. Method according to claim 1 or 2 in which at least the mortar layer is reinforced by means of reinforcing bars, characterized in that prior to spraying of the ribs (18, 19, 20) reinforcing bars (23) for the ribs (18, 19 20) are placed between temporarily mounted side casing plates (24, 25), which plates (24, 25) are removed prior to the spraying of the final layer or layers (26) of the ribs (18, 19, 20).