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This invention relates to a method of forming a swimming pool construction. 
     BACKGROUND OF THE INVENTION 
     Various different designs and construction techniques have been used for manufacture of excavated or in ground pool constructions. One technique uses cast concrete reinforced by reinforcing steel for constructing the base and walls of the pool. The inside surface of the concrete is then suitably coated or lined with tiles. This form of construction has been widely used in commercial pools which tend to be significantly larger and require much stronger construction to accommodate relatively large amounts of people and water involved in such larger pools. However the concrete construction is relatively expensive and in some soil conditions has significant problems of cracking due to soil movement. Relatively large costs can therefore be expected in renovation work after the initial cost of installation. 
     A common technique for constructing pools for backyard or home use involves the installation of walls formed from metal panels which are then reinforced by inclined braces. After installation, the space between the excavated soil and the outside surface of the metal panel is then filled with suitable filling material so that the forces from the water on one side of the metal panel are to some extent balanced by inward forces from the soil and filling material on the outside of the metal panel. A covering layer is then applied to the excavated pool base and a liner of a suitable plastics material is applied over the covering layer and over the metal walls to contain the water. 
     Pools of this type are generally satisfactory for lightweight home use in which the dimensions of the pool are relatively small but it is generally accepted that pools of this construction are not acceptable for large scale commercial size pools due to the instability of the structure. In addition pools of this type generally cannot be emptied due to the necessity to maintain a balance between the outward pressure of the water and the inward pressure from the soil. If the water is removed therefore there is a significant danger of collapse. 
     However it is also well known that the metal fabricated structure is significantly cheaper than the concrete formation and does not suffer from the very heavy costs of renovation or repair which can become necessary with the concrete structure. 
     Canadian Patent application 2,125,748 of the present inventor filed Jun. 13, 1994 and published December 1994 discloses a construction for a swimming pool which has inner and outer metal wall panels defining a space between. This construction has achieved some commercial success but is relatively difficult to assemble and to manufacture requiring considerable labour costs. 
     French patent application 1529616 shows a similar double wall construction fabricated from wood and metal elements but this is not suitable for rapid assembly. 
     U.S. Pat. No. 4,120,126 (West) issued Oct. 17, 1978 discloses a pool wall constructed from metal and wood components having an inner wall and an outer supporting element which is filled with soil between the two elements. 
     U.S. Pat. No. 4,090,266 (Price) issued May 23, 1978 discloses a pool wall construction in which the wall is supported by concrete posts cast around junctions between the wall panels and connected to a horizontal cast base. 
     U.S. Pat. Nos. 3,820,174 (Rozanski) issued Jun. 28, 1974, 4,007,566 (Molitor) issued Feb. 15, 1977, 4,050,104 (Baker) issued Sep. 27, 1977, 3,391,790 (Lerner) issued Jul. 9, 1968, 4,109,324 (Cornelius) issued Aug. 29, 1978, 4,407,102 (Boyack) issued Oct. 4, 1983 and 5,425,145 (Baker) issued Jun. 20, 1995 all show various swimming pool constructions. 
     U.S. Pat. No. 2,741,910 (Thornely) issued Apr. 17, 1956 discloses a building foundation using piles. 
     None of the above constructions however provide a modular assembly which can be rapidly and easily assembled and can be completed by pouring concrete to form the necessary structural elements. 
     SUMMARY OF THE INVENTION 
     It is one object of the present invention, therefore, to provide an improved swimming pool construction which enables the advantages of the metal fabricated structure to be used in the large scale commercial size swimming pool while providing forming structures which can be readily removed and reused after the concrete structure has been cast for metal walls. 
     According to a first aspect of the invention, therefore, there is provided a method of forming a swimming pool construction having a peripheral pool wall of a predetermined pool shape comprising: 
     providing a plurality of ground anchor members arranged at longitudinally spaced positions around the predetermined pool shape and at a common levelled height; 
     the ground anchor members including an inner row and an outer row spaced at a common distance outwardly relative to the pool shape from the inner row; 
     providing on each of the inner row of the ground anchor members an inwardly extending inner support member; 
     providing on each of the outer row of the ground anchor members an outwardly extending outer support member; 
     providing a plurality of inner rail members and a plurality of outer rail members each having a bottom support surface and a vertical abutment surface; 
     arranging the inner rail members end to end and mounting the inner rail members with the horizontal flange thereof supported on the inner support members to follow the pool shape, the vertical abutment surface of the inner rail members oriented to define an outwardly facing retaining surface; 
     arranging the outer rail members end to end and mounting the outer rail members with the horizontal flange thereof supported on the outer support members to follow the pool shape, the vertical abutment surface of the outer rail members oriented to define an inwardly facing retaining surface; 
     providing a plurality of inner pool wall panels; 
     locating a bottom edge of the inner pool wall panels on the inner rail members at the outwardly facing retaining surface of the inner rail members so as to stand upwardly therefrom and connecting the inner wall panels end to end to form an inner pool wall; 
     supporting the inner pool wall panels so as to stand vertically upwardly from the inner rail members; 
     casting a concrete base layer between the outwardly facing retaining surface of the inner rail members and the inwardly facing retaining surface of the outer rail members such that the concrete base layer engages the bottom edge of the wall panels; 
     and removing the inner and outer rail members leaving the wall panels supported in place on the concrete base layer. 
     Preferably each of the inner and outer rail members comprises an angle member defining a vertical flange forming the vertical abutment surface and a horizontal flange forming the bottom support surface and wherein the flange is located underneath the bottom edge of the inner pool wall panels so as to provide support therefor. 
     Preferably the bottom edge of the inner wall panels includes an outwardly turned edge flange member. 
     Preferably a horizontal flange of the rail member rests upon the inner support member and is temporarily attached thereto. 
     Preferably a substantially horizontal floor panel extends across and rests upon the horizontal flange members for supporting the concrete layer when cast. 
     Preferably the inner pool wall panels have a bottom flange resting upon an edge of the horizontal floor panel at the vertical abutment surface. 
     Preferably the ground anchor members are formed of cast concrete having a flat supporting top surface; wherein the inner and outer support member have an upper support surface of the support member flush with the respective flat top surface; wherein there is provided a plurality of floor panels which are located so as to span between the vertical abutment surfaces of the inner and outer rail members and so as to rest upon the inner and outer rail members and closely adjacent the flat top surfaces of the cast concrete ground anchor members; wherein holes are cut in the floor panels at the flat top surfaces of the ground anchor members and wherein the concrete base layer is cast on the floor panels between the outwardly facing retaining surface of the inner rail members and the inwardly facing retaining surface of the outer rail members and through the holes such that the concrete base layer rests upon and receives support from the flat top of the cast concrete ground anchor members. 
     Preferably the inner and outer support members are each defined by a U-shaped channel member with legs thereof facing upwardly so that the horizontal flanges rest thereon. 
     Preferably the method includes: 
     providing a plurality of outer pool wall panels; 
     locating a bottom edge of the outer pool wall panels on the outer rail members at the inwardly facing retaining surface of the outer rail members so as to stand upwardly therefrom and connecting the outer wall panels end to end to form an outer pool wall; 
     supporting the outer pool wall panels so as to stand vertically upwardly from the outer rail members; 
     the inner and outer wall panels being supported by: 
     forming a plurality of arch members each having a first leg at a respective one of the inner wall panels, a second leg at a respective one of the outer wall panels and a cross piece; 
     the legs of the arch member comprising a channel shaped structure having a pair of side walls spaced along the panel and a web wall spanning the side walls and spaced from the respective panel; 
     the cross piece of the arch member comprising a channel shaped structure having a pair of side walls spaced along the inner and outer panels and a web wall spanning the side walls and spaced downwardly from a top edge of the side walls; 
     casting a concrete arch into the arch member such that one leg of the arch is connected to the inner panel and the other leg of the arch is connected to the outer panel; 
     and removing the arch members such that the inner and outer wall panels are supported by the cast concrete arches. 
     Preferably the method includes forming the arch member in two parts each defined by one side wall of the cross piece and one side wall of each of the legs and one portion of the web of the cross piece and each of the legs such that the two parts are connected together along a seam across the webs of the legs and the crosspiece, the arch member so formed being rigid so that the legs are retained at right angles to the cross piece to hold the inner and outer panels parallel and at a required spacing; 
     Preferably the method includes casting the arches and the base layer substantially simultaneously such that setting occurs simultaneously to form an integral structure. 
     Preferably the method includes providing the arch members at the bottom of the legs thereof with an open mouth and forming the base layer to a level substantially equal to the bottom of the legs so as to be integral with the cast arch and allowing the arch member to be removed from the arch and from the base layer. 
     Preferably the method includes forming for each leg of each arch member on the respective one of the inner and outer wall panels a pair of parallel vertical flanges and bolting the sides of the leg to the flanges for casting of the arch and for subsequent removal of the arch member. 
     Preferably the method includes providing a plurality of top supporting panels and supporting each support panel on the arches across the inner and outer wall panels and between the arches and casting a concrete cover layer over the support panels. 
     Preferably the method includes supplying the rail members in a pre-curved shape to match said predetermined pool shape and supplying the panels in a flat shape for curving to match the rail members. 
     According to a second aspect of the invention, therefore, there is provided a method of forming a swimming pool construction having a peripheral pool wall of a predetermined pool shape comprising: 
     providing a plurality of cast concrete ground anchor members arranged at longitudinally spaced positions around the predetermined pool shape and at a common levelled height; 
     the cast concrete ground anchor members including an inner row and an outer row spaced at a common distance outwardly relative to the pool shape from the inner row; 
     the cast concrete ground anchor members having a supporting top surface; 
     providing on each of the inner row of the ground anchor members an inwardly extending inner support member having an upper support surface of the support member flush with the top surface; 
     providing on each of the outer row of the ground anchor members an outwardly extending outer support member having an upper support surface of the support member flush with the top surface; 
     providing a plurality of inner rail members and a plurality of outer rail members; 
     arranging the inner rail members end to end and mounting the inner rail members supported on the inner support members to follow the pool shape; 
     arranging the outer rail members end to end and mounting the outer rail members supported on the outer support members to follow the pool shape; 
     providing a plurality of floor panels and locating the floor panels so as to span between the inner and outer rail members and so as to rest upon the inner and outer rail members; 
     providing a plurality of inner pool wall panels; 
     locating a bottom edge flange of the inner pool wall panels on an outer edge of the floor panels at the inner rail members so as to stand upwardly therefrom and connecting the inner wall panels end to end to form an inner pool wall; 
     supporting the inner pool wall panels so as to stand vertically upwardly from the inner rail members; 
     cutting holes in the floor panels at the ground anchor members; 
     casting a concrete base layer on the floor panels between the inner rail members and the outer rail members and through the holes such that the concrete base layer rests upon and receives support from the flat top of the cast concrete ground anchor members; 
     and removing the inner and outer rail members leaving the wall panels supported in place on the concrete base layer. 
     Preferably the inner and outer support members are each defined by a U-shaped channel member with legs thereof facing upwardly so that the horizontal flanges rest thereon. 
     According to a third aspect of the invention, therefore, there is provided a method of forming a swimming pool construction having a peripheral pool wall of a predetermined pool shape comprising: 
     providing a plurality of inner pool wall panels; 
     locating and supporting the inner pool wall panels so as to stand generally vertically upwardly and to follow the predetermined pool shape; 
     and supporting the inner wall panels by: 
     forming a plurality of arch members at spaced positions around the pool each having a first leg at a respective one of the inner wall panels, a second leg spaced outwardly from the inner wall panels and a cross piece; 
     the legs of the arch member comprising a channel shaped structure having a pair of side walls spaced along the respective panel and a web wall spanning the side walls and spaced from the respective panel; 
     the cross piece of the arch member comprising a channel shaped structure having a pair of side walls spaced along the inner and outer panels and a web wall spanning the side walls and spaced downwardly from a top edge of the side walls; 
     temporarily attaching edges of one of the legs to the inner panels; 
     casting a concrete arch into the arch member such that one leg of the arch is connected to the inner panel; 
     casting a concrete floor connected with the concrete arch; 
     and removing the arch members such that the inner wall panels are supported by the cast concrete arches and the concrete floor. 
     Preferably the method includes forming the arch member in two parts each defined by one side wall of the cross piece and one side wall of each of the legs and one portion of the web of the cross piece and each of the legs such that the two parts are connected together along a seam across the webs of the legs and the crosspiece; the arch member so formed being rigid so that the legs are retained at right angles to the crosspiece to hold the inner and outer panels parallel and at a required spacing. 
     According to a fourth aspect of the invention, therefore, there is provided a method of forming a swimming pool construction having a peripheral pool wall of a predetermined pool shape comprising: 
     providing a plurality of inner pool wall panels; 
     providing a plurality of outer pool wall panels; 
     locating and supporting the inner pool wall panels so as to stand generally vertically upwardly and to follow the predetermined pool shape; 
     locating and supporting the outer pool wall panels so as to stand generally vertically upwardly and to follow the inner wall panels at a position spaced outwardly therefrom; 
     and supporting the inner and outer wall panels by: 
     forming a plurality of arch members at spaced positions around the pool each having a first leg at a respective one of the inner wall panels, a second leg at a respective one of the outer wall panels and a cross piece; 
     the legs of the arch member comprising a channel shaped structure having a pair of side walls spaced along the respective panel and a web wall spanning the side walls and spaced from the respective panel; 
     the cross piece of the arch member comprising a channel shaped structure having a pair of side walls spaced along the inner and outer panels and a web wall spanning the side walls and spaced downwardly from a top edge of the side walls; 
     temporarily attaching edges of the legs to the inner and outer panels respectively; 
     casting a concrete arch into the arch member such that one leg of the arch is connected to the inner panel and the other leg of the arch is connected to the outer panel; 
     casting a concrete floor connected with the concrete arch; 
     and removing the arch members such that the inner and outer wall panels are supported by the cast concrete arches and the concrete floor. 
     Preferably the method includes forming the arch member in two parts each defined by one side wall of the cross piece and one side wall of each of the legs and one portion of the web of the cross piece and each of the legs such that the two parts are connected together along a seam across the webs of the legs and the crosspiece; the arch member so formed being rigid so that the legs are retained at right angles to the cross piece to hold the inner and outer panels parallel and at a required spacing. 
     According to a fifth aspect of the invention, therefore, there is provided a method of forming a swimming pool construction having a peripheral pool wall of a predetermined pool shape comprising: 
     providing a plurality of inner pool wall panels; 
     providing a plurality of outer pool wall panels; 
     locating and supporting the inner pool wall panels so as to stand generally vertically upwardly and to follow the predetermined pool shape; 
     locating and supporting the outer pool wall panels so as to stand generally vertically upwardly and to follow the inner wall panels at a position spaced outwardly therefrom; 
     and supporting the inner and outer wall panels by: 
     providing a plurality of rigid arch members at spaced positions around the pool shape each having a first leg at a respective one of the inner wall panels, a second leg at a respective one of the outer wall panels and a cross piece; 
     providing a rigid horizontal floor; 
     and providing a top cover member; 
     such that the rigid arch members support the walls and form with the top cover and the floor a crawl space surrounding the pool. 
     According to a sixth aspect of the invention, therefore, there is provided a method of forming a swimming pool construction having a peripheral pool wall of a predetermined pool shape comprising: 
     providing a plurality of inner pool wall panels; 
     supporting the inner pool wall panels so as to stand vertically upwardly and to follow the predetermined pool shape; 
     providing at a top edge and a bottom edge respectively of the inner wall panels an edge flange member turned at an angle to the inner wall panel so as to project outwardly therefrom to an outermost edge of the edge flange member; 
     providing in the edge flange member a plurality of slots therein extending from the outermost edge to the panel; 
     and bending of the panel about vertical lines in the panel with the slots allowing said bending. 
     Preferably the inner wall panels are attached to bottom supporting rail members and including supplying the rail members in a pre-curved shape to match said predetermined pool shape and supplying the panels in a flat shape for curving to match the rail members. 
     Preferably the method includes embedding the flange member at the bottom edge in the concrete base layer and embedding the flange member at the top edge in a concrete cover layer. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     One embodiment of the invention will now be described in conjunction with the accompanying drawings in which: 
     One embodiment of the invention will now be described in conjunction with the accompanying drawings in which: 
     FIG. 1 is a vertical cross sectional view transversely of a swimming pool construction according to the present invention. 
     FIG. 2 is a cross sectional view similar to that of FIG. 1 but taken at a location spaced around the periphery of the pool. 
     FIG. 3 is a cross-sectional view along the lines  3 — 3  of FIG.  2 . 
     FIG. 4 is a cross sectional view taken along the lines  4 — 4  of FIG.  3 . 
     FIG. 5 is a cross sectional view taken along the lines  5 — 5  of FIG.  3 . 
     FIG. 6 is a cross sectional view taken along the lines  6 — 6  of FIG.  3 . 
     FIG. 7 is an isometric view of the flange member on the top or bottom edge of the wall panels showing the bending effect. 
     FIG. 8 is a cross sectional view along the lines  8 — 8  of FIG.  7 . 
     FIG. 9 is the same cross sectional view as FIG. 1 with the concrete cast in place and the rails and arch members removed. 
     FIG. 10 is the same cross sectional view as FIG. 2 with the concrete cast in place and the rails and arch members removed. 
     FIG. 11 is a cross sectional view similar to that of FIG. 1 showing a simplified construction for use with smaller pools where the double wall construction is not required. 
     FIG. 12 is a cross sectional view similar to that of FIG. 11 with the concrete added and the supports removed. 
     FIGS. 13 to  17  each show an isometric view of a respective one of the various stages of a second embodiment of the construction method according to the present invention. 
     FIG. 18 is a cross sectional view of the construction of FIGS. 13 to  17 . 
    
    
     In the drawings like characters of reference indicate corresponding parts in the different figures. 
     DETAILED DESCRIPTION 
     The pool construction in FIGS. 1 through 8 comprises a modular construction which can be used as a temporary installation using the construction elements as shown or can be used as a permanent installation in which the modular construction is used as a form for the addition of concrete structural members cast in place. 
     In FIGS. 1 through 10 is shown a double wall construction which is suitable for larger pool construction of the type normally used for public installations such as hotels, recreation complexes and the like. This construction provides a crawl space between the double wall construction through which the pipes can pass to supply the large quantity of water necessary for moving in a large area pool. The construction shown in FIG. 11 uses similar construction techniques to that shown in FIGS. 1 through 10 and as described hereinafter but can be used for smaller size pools where the quantity of water to be moved is insufficient to justify the extra expense of the double wall and crawl space construction. 
     The modular construction comprises a support base generally indicated at  10 , a pair of side rails  11  and  12  carried on the support base, an inner wall structure  13 , an outer wall structure  14  and a plurality of arch members  15 . The wall structures  13  and  14  are carried on the side rails  11  and  12  and the wall structures are supported in vertical square orientation by the arch members  15 . 
     In a temporary installation, the support base  10  can be provided simply a flat surface such as the concrete surface of an arena, a paved parking lot or the like. 
     In a permanent installation, the support base  10  is provided by an inner row  16  of anchor members and an outer row  17  of anchor members. 
     Each anchor member comprises as shown a concrete pile  18  which has cast into it a vertical post  19  with a horizontal support  20  attached to the top of the post. Preferably the post  19  is formed from an angle iron which is welded to a similar angle iron forming the support  20  which is held therefore at right angles to the post and provides a horizontal flange defining one side of the angle iron onto which the respective rails  11 ,  12  can be supported. 
     As an alternative to the angle iron post and support arrangement, the rebar in the pile can be bent at right angles to form a horizontal support. As a yet further alternative other forms of anchor can be used. In mounting the anchors in the ground or providing the other form of base support, careful levelling is applied so that the horizontal support surfaces on which the rails are mounted are at a common height. 
     In the embodiment as shown, the piles  16  and  17  are located at a spacing inwardly of the intended location of the rails with the horizontal support portion turned outwardly and extending outwardly from the piles. Thus the piles are located at a position substantially directly underneath the wall structures  13  and  14  so as to provide effective support of those wall structures and to communicate forces from those wall structures to the ground. 
     The rails  11  and  12  are generally C-shaped in cross section with a top horizontal flange  21 , a bottom horizontal flange  22  and a substantially vertical back wall  23 . The flanges  21  and  22  have downturned inward edges to provide a stiffening effect of the rails. The rails can be further stiffened by vertical webs  24  arranged at the ends of the rail portions and intermediate end. The rails are formed in separate rail portions each forming a part of the periphery of the pool shape. The rails are pre-formed in curved shapes suitable for manufacturing a predetermined pool shape. 
     The pool shape can be complex including compound curvatures or can be a simple shape which is substantially oval or rectangular depending upon requirements. Whatever the predetermined shape of the pool that is required, the individual rail portions are formed to the required shapes so when connected end to end form the complete peripheral shape that is required. 
     Of course the location of the piles or other anchor structure is arranged in the initial layout of the pool structure so that the piles also follow the intended pool shape with the inner rail and the inner row of anchors located at the inner wall of the pool and therefore actually constituting the shape of the pool and the outer anchors and the outer rail following the inner shape but spaced at a constant distance outwardly therefrom. 
     When the pool has reached its intended shape and the rails and piles have been placed in their respective positions the walls  13  and  14  are fixed to the appropriate rail. The walls are attached to the vertical back wall  23  and are supported in place with a first horizontal steel bar  26 . The horizontal steel bar  26  is inserted through the bottom end  28  and  29  of the walls  13  and  14  and is then fixed to the vertical back wall  23  of the rails  11  and  12 . 
     A second horizontal steel bar  26 A is located below first horizontal steel bar  26 . The second bar  26 A is attached to the rails for increased support for the pool structure. The first bar  26  and the second bar  26 A are positioned in a staggered manner wherein a first bar  26  is positioned ahead of the second bar  26 A and so forth. 
     Located below the second bar  26 A is a horizontal floor portion  31  which extends horizontally from either vertical back wall  23  of the rails and runs the length of the pool structure. The floor portion is supported by a first row of tabs  32 . The floor portion  31  is positioned such that it directs the flow of concrete so that the concrete is poured correctly, as described later. 
     The inner wall structure  13  has a second top flange  33 A located at the further most top end  28 A. The top flange  33 A is located on the top end  28 A of the inner wall structure  13  and extends horizontally inward. A second bottom flange  35 A and  35 B is located at the furthermost bottom end  28  and  29  of the wall structures. The second bottom flange  35 A is located at the bottom end  28  of the inner wall structure  13  and extends horizontally inward. The second bottom flange  35 B is located on the bottom end  29  of the outer wall structure  14  and extends horizontally inward. 
     Located on the second top flange  33 A is coping  37 A. The coping  37 A is mounted on the top edge  39 A if the flange  33 A. The coping is fixed to the flange by an L-shaped member  41 A. The first L-shaped member  41 A is located on the top edge  39 A of the flange  33 A and is positioned so that the back side  43 A is facing inward. 
     The coping  37 A on the flange  33 A consists of a first recess  45 A in which the back side  43 A is inserted and tightened with a bolt  47 A. The coping  37 A has a second recess  49  which is positioned and appropriately sized so that the liner for the pool can be inserted and held. The coping has a top ledge  51 A. 
     Located slightly below the flange  33 A is a plurality of second tabs  77  which extends horizontally inward from the inner wall structure  13 . The tabs  77  are positioned such that the top floor portion  79  can be mounted. The top floor portion  79  extends horizontally inward and to the outer wall structure  14  and rests on the top end  29 A of the outer wall  14 . The outer wall structure  14  is of a shorter length than the inner wall structure such that the second tabs  77  are higher than the outer wall  14  to allow the top floor portion  79  to be positioned at a slight angle downward and in a direction away from the inner wall  13  to allow water and the like to flow away from the pool water. As best shown in FIG.  2 . 
     When the concrete generally indicated at  53  is applied to the structure it is poured into the top opening  55  of the arch member  15 . The concrete  53  is directed downwardly until it reaches the top shelf  57  which extends horizontally across the arch member  15 . A first wall  59  extends vertically downwardly from one end of the top shelf  57  to the bottom end  63  of the arch member  15  and is parallel to the inner wall structure  13 . The second wall  61  extends vertically downwardly from one end of the top shelf to the bottom end  63  of the arch member  15  and is parallel to the outer wall structure  14 . The walls  59  and  61  are parallel to each other and are of equal size. 
     Outside arch walls  65 A and  65 B surround the arch member  15 . The outside wall  65 A is located on the front side  67  of the arch member  15 . The outside wall  65 B is located on the back side  69  of the arch member  15 . The outside wall  65 A and  65 B are parallel and are of equal size. 
     The arch member has a top opening  55  and two bottom openings  71 A and  71 B. The bottom opening  71 A and  71 B are on opposing sides of the structure being located at the furthermost bottom end of the arch member  15 . The bottom openings allow the concrete to flow through to the floor portion filling the structure with concrete. The concrete is directed to flow into the arch member  15  and to be level with the bottom of the arch member leaving the center open portion  73  to act as a crawl space for hoses and the like to be ran through the pool structure. 
     The floor portion  31  has a plurality of holes  75  which is shaped accordingly to allow the concrete to flow correctly into the assigned position designed to support the structure. When the concrete is set the side rails  11  and  12  are removed and the horizontal support  20  on the inner row anchor  16  and outer row anchor  17  is cut so that the horizontal support  20  is flush with the extended anchor  16 B. 
     The arch member  15  is removed when the concrete is set. 
     In order to enable the pool structure to be built to the desired shape the inner wall structure  13  and the outer wall structure  14  must be able to bend and form to the desired shape. The flange  33 A and the bottom flanges  35 A and  35 B consist of slotted portions  81 . The slots  81  allow the walls  13  and  14  to be formed and bent. To bend and form the walls  13  and  14  the flange slots  81  can be manipulated such that the slots separate, as best shown in FIGS. 7 and 8. In FIG. 7 the slots are separated so that the inner or outer wall structure can bend putting the flange on the convex side. In FIG. 8 the individual slots are bent upward and downward such that the inner and outer wall can bend putting the flange on the concave side. 
     A similar arrangement to the slots  81  is found on the rails  11  and  12 . The rails  11  and  12  have a second arrangement of slots  83  found on the top horizontal flange  21  and on the bottom horizontal flange  22 . The slots  83  allow the rails to be manipulated to form the desired shape or form. The slots  83  separate when the rail is formed such that the slots  83  are found on the convex side. The individual slots  83  are bend upward and downward such that the rails can be forms putting the slots  83  on the concave side. 
     When the slots are on the same side the first arrangement of slots  81  are separated and on the convex side the second arrangement of slots  83  are positioned in the up and down position and on the concave side. When the first arrangement of slots  81  are in the up and down position and on the concave side the second arrangement of slots  83  are separated and on the convex side. 
     The embodiment in FIG.  1  and FIG. 9 show the pool structures construction which is formed to be an island or the like for the pool. The outer wall structure  14  is the same as the inner wall structure and the concrete reaches an equal height as the coping. 
     The embodiment in FIG.  11  and FIG. 12 shows the pool structure which the outer wall structure  14  is removed. The outer wall is not necessary is construction of smaller pools. The arch member  15  is removed and replace with a single sided construction  85 . A support arm  87  holds the structure stable while in the first stages and is removed when the concrete is added, as best shown in FIG.  12 . 
     Turning now to the embodiment shown in FIGS. 13 through 18, this shows a yet further improved arrangement modified relative to the above described embodiment to provide a series of important advantages which allow a significant reduction in labour costs and material costs in manufacturing the construction. 
     Various stages of the construction as shown in FIGS. 13 through 17 and the completed assembly prior to removal of the forming elements is shown in FIG.  18 . 
     Turning firstly to FIG. 13, an initial stage of the construction involves the excavation of the ground to provide the recessed area  100  within which the pool is to be constructed. Within this area is formed a plurality of concrete piles  101  which are engaged into the ground below the new excavated level  102  and project upwardly from level  102  to provide a cylindrical pile body with a top surface  104 . The piles are arranged to form an inner row  105  and an outer row  106 . In the area shown in FIG. 13 where the is a curved section of the pool, the piles are arranged so that each is paired with another in the outer row. However in places where the pool wall is straight, the piles can be alternated so that there is a pile in the inner and the next pile on the outer row is in between the two piles on the inner row. 
     Each pile when cast includes conventional reinforcing bars  108  which project outwardly beyond the top of the pile and in addition there is provided a channel member  109  which is embedded in the top surface  104  so that the channel member has a flat web within the concrete and two upstanding side walls which stand up to the same height as the top flat surface  104  upper pile. The channels  109  of the inner row  105  project inwardly relative to the pool construction and the channels  109  of the outer row of piles project outwardly relative to the pool construction. 
     A plurality of inner rails  110  are located on the channel supports  109  at a position for defining the location of the inner pool wall. These inner rails are temporarily attached to the channel supports  109  and arranged end to end to form a complete rail track extending around the periphery of the pool. The temporary attachment can be carried out by tack welding or by other suitable coupling devices. 
     Similarly corresponding outer rails  111  are located on the outer channel support members and follow the path of the pool periphery at a constant spacing around the pool periphery so as to define a constant spacing between the intended position of the inner wall and the intended position of the outer walls. 
     Each of the rails is formed by a right angle member defining a simple vertical flange  112  and a simple horizontal flange  113  so that the rails are of simple inexpensive construction. The horizontal flange sits directly on top of the channel support member and the vertical flange stands upwardly therefrom. The vertical flange is arranged facing inward for the inner rails and facing outward for the outer rails so as to define an area therebetween defined by the two upstanding vertical flanges. 
     In the next phase shown in FIG. 14 a series of floor panels  114  are applied over the piles with each floor panel spanning the distance between the vertical flanges  112  so that edges of the floor panels sit on the horizontal flanges  113 . 
     With the floor panels in place, the inner and outer wall panels  115  and  116  respectively are applied onto the edges of the floor panels at the horizontal flanges  113  of the inner and outer rails respectively. Each wall panel has a bottom flange  117  and a top flange  118  turned at right angles to the surface of the wall panel. Similarly each wall panel has side flanges  120  also turned inwardly at right angles. The top and bottom flanges as previously described are notched so as to allow the panels to be bent to follow the shape of the rails without the necessity for pre-forming the wall panels into the required shape. Thus the wall panels can be supplied in flat form and matched on site to the required curvature to follow the rail to which it is to be attached. 
     The flanges  117  sit on top of the floor and a series of fasteners are applied through the bottom flange  117  into the floor so as to fasten the bottom flange and therefore the wall panel to the floor so as to stand upwardly therefrom. The outside surface of the wall panel butts against the vertical flange  112 . 
     As previously described, the walls panels after bending to the required shape are arranged edge to edge so that the side flanges  120  are engaged each with the next panel and the side flanges are connected by suitable screw fasteners to hold the structure temporarily upright. In order to maintain the wall panels vertical, a plurality of arch form members  125  at spaced positions along the length of the pool periphery. Each arch form member is formed in two separate pieces defining a left half and a right half respectively joined along a seam line  126 . Each half forms a rigid structure defining one half of the vertical leg at the inner wall and one half of the vertical leg at the outer wall together with one half of the truss piece. Thus each half comprises a web section for each of the legs on the cross piece together with a vertical flange for each of the legs in the cross piece. At the seam  126  is provided a flange  127  which projects from the channel member at right angles so that the two flanges  127  side by side can be bolted together to form the channel form member into the complete rigid structure. The wall panels include attached angle members  128  adjacent the edge flanges  120  and these provide a flange at right angles to the wall panel so that the edges of the vertical flanges of the channel form members can be fastened temporarily to the angle members  128  by a plurality of fasteners along the height of the arch form member. The bottom edge of the arch form member  129  is spaced upwardly from the floor panel  114  by a distance equal to and intended thickness of the floor pad. 
     In view of the fact that the arch form members are rigid in structure defined by the two halves each of which forms integrally to legs and the cross piece ensures that the arch form member when bolted together and when bolted to the side walls is rigid and holds side walls rigid and parallel. 
     With the side walls now held secure, holes are cut in the floor panels at locations immediately on top of the piles  101  so that the top  104  of the pile is exposed through the floor. This also leaves reinforcing bars  108  exposed at the top and exposed into or through the floor. 
     Through the floor is applied a tubular forming member  130  which includes a top portion  131  sitting on top of the floor and a cylindrical portion extending downwardly around the pile so as to provide a connection between the pile and the top of the floor. With the arch form members in place, reinforcing bars  135  are laid on top of the floor  114  at a height spaced from the floor so as to provide reinforcing bars in the center area of the intended layer of concrete. Further reinforcing bars  136  are applied through the arch members in a loop surrounding the arch members so as to provide the bottom part of the reinforcing bars within the floor and an arch portion of the reinforcing bar through the arch member. Further reinforcing bars  137  are applied in the cross piece of the arch member and stand upwardly from the top of the arch member in a C shaped loop to form a section in a top cap to be subsequently cast. 
     With the reinforcing bars in place, it is poured into the floor section between the arch members and is poured down each leg of each arch member and onto the cross piece of each arch member to form an integral concrete structure defined by the floor and the plurality of arches. 
     With the concrete cast and set, the arch form members can be removed by disconnecting the fastenings from the angles  120  on the side walls and disconnecting the flanges  127  thus releasing the two halves which can be broken away from the concrete and pulled out from the interior for reuse. 
     In addition the angle members  110  and  111  defining the rails can simply be pulled out after breaking the temporary attachment to the channel support members  109 . Again therefore the rails are readily available for re use. 
     The casting of the floor onto the piles ensures that the floor is integrally connected with the piles so that the whole structure including the floor and the arches form the rigid structure holding the inner and outer wall panels rigid. 
     A top cover is formed by applying a plurality of cover panels  140  onto the top of the arches after they are cast. The panels  140  extend from the top flange  118  at the top of the rear panel to an intermediate support flange  142  on the front panel spaced downwardly from the top flange  118  of that panel. The cover sheets  140  thus bridge the areas between the arches and allow a concrete pad  144  to be cast on top of the arches and on top of the cover panels. The cast concrete pad includes reinforcing bars  146  of a conventional nature and engages into the upper part of the bars  137  which thus integrate the arches with the cast concrete cap. 
     The remaining structure thus after removal of the forming elements defined by the arch members and the rails is of a simplified structure with much of the structure being reusable. In fact the floor panels and the cover panels can also be removed in many cases simply by pulling them from underneath the concrete when cast. 
     Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without departing from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.

Summary:
A swimming pool construction is of the type using metal fabricated walls and a plastics liner covering the walls and a rigid excavated pool base. The metal fabricated walls include spaced inner and outer panels defining therebetween a crawl space. The inner panels define the inner surface of the pool. The outer panels engage the surrounding soil. The panels are mounted on support members and rails supported on pairs of piles at spaced positions around the periphery of the pool. The panels are supported initially on bottom rails which are used as forms to cast a concrete layer therebetween. The panels are supported in spaced positions temporarily by a rigid arch form into which is cast a cast concrete arch allowing the rails and the arch form to be removed for re-use. The arch is cast integrally with a concrete floor which sits on supporting panels bridging the rails and resting on flat top supporting surfaces of the concrete piles. A top concrete cover is cast onto bridging panels spanning between the inner and outer walls and carried on the top of the arches.