WO2009150227A1

WO2009150227A1 - Method and apparatus for forming watertight panels in building foundations, special foundations, cutoff walls and similar constructions

Info

Publication number: WO2009150227A1
Application number: PCT/EP2009/057290
Authority: WO
Inventors: Alberto Perencin
Original assignee: Otium & Business S.R.L.
Priority date: 2008-06-13
Filing date: 2009-06-12
Publication date: 2009-12-17
Also published as: EP2319989A2; ITPN20080047A1

Abstract

The present invention relates to a method and an apparatus (5) for forming watertight panels in building foundations, special foundations, cutoff walls and similar constructions, comprising the steps of : -forming a cavity (3) in the soil (2) having a substantially parallelepipedal shape by means of excavating means (1); -concurrently with the removal of the soil material, progressively pouring a stabilization and temporary-filling material (4) into the cavity (3); -upon completing the excavation step, introducing in correspondence of at least a wall of the cavity (3) an expandable apparatus (5) delimiting the wall and removably provided with watertight coupling means (8), the apparatus (5) being brought to an expanded condition outside or inside the cavity (3); -casting concrete (10) into the cavity (3) while concurrently removing the stabilization and temporary-filling material (4) therefrom, so as to form a first foundation panel (11); -bringing the expandable apparatus (5) to a retracted condition and removing the apparatus (5) from the cavity (3) so as to obtain a hollow space (12) between a flank of the first panel (11) and the wall of the cavity (3).

Description

METHOD AND APPARATUS FOR FORMING WATERTIGHT PANELS IN BUILDING FOUNDATIONS, SPECIAL FOUNDATIONS, CUTOFF WALLS AND

SIMILAR CONSTRUCTIONS

DESCRIPTION

The present invention relates to a method and an apparatus for forming watertight panels in building foundations, special foundations, cutoff walls and similar constructions.

A method that is largely used and widely known in the art nowadays for forming panels of the above-noted kind consists in using suitable excavating means, such as excavating buckets or punctual ground borers depending on the characteristics of the ground to be dug through, to excavate a first sequence of cavities in the shape of substantially a parallelepiped, the cross-section of which substantially corresponds to the nominal size of the excavating tool or a multiple of such size; these cavities are arranged duly spaced from each other all along the project perimeter to be encircled with the foundations at a distance that is approximately equal to the width thereof as measured along the above-mentioned perimeter. Concurrently with the removal of the excavation material, a stabilization and temporary-filling material, such as bentonite or bentonite slurry, is progressively introduced into the cavity being dug to stabilize and temporarily filling the same. When the due project depth of the cavity is eventually reached, the process goes on by first fitting in the iron rods forming the metal reinforcement work in each thus obtained cavity, duly filled with bentonite, and then casting concrete thereinto until the bentonite is fully removed out of the cavity. These cavities thus provided in a mutually spaced arrangement all along the foundation perimeter, and reinforced with cast concrete, form the so-called "primary" panels.

Once the perimeter to be encircled with the foundations has been defined by laying down said "primary" panels, the process is continued by forming the so- called "secondary" panels which connect pairs of adjacent "primary" panels with each other, through the removal of material - again with the use of excavating buckets or special ground borers/drillers - in the portion of soil between a "primary" panel and the next one so as to dig out a cavity having a size and a shape that are substantially similar to those of the adjacent cavities; during excavation, also these cavities are filled with bentonite, reinforced with iron rods and eventually cast with concrete, in the same manner as described above in connection with the working steps followed in forming the "primary" panels, to the purpose of providing a continuous sequence of primary and secondary panels duly joined with each other and closing in this way the foundation perimeter.

A major drawback that is generally encountered in the above-described method lies in the fact that the excavation work for forming the secondary panels unavoidably involves removing a portion of the flanks of the concrete casting of the pre-existing primary panels, due to the irregular shape of said flanks mainly caused by soil particles included therein as such panels were being formed. Such undesired removal can be most readily appreciated to entail an economically significant loss due to the wastage of concrete material incurred, further to impairing the qualitative integrity of the bentonite slurries in a way that is likely to prove prejudicial to the recovery of such slurries for further use. In fact, the concrete particles that get mixed in the bentonite slurries cause the specific density and weight of these slurries to be increased, so that they tend to precipitate onto the bottom of the cavity, instead of remaining in a suspension therein. Owing to this, they will therefore no longer be able to be driven out of the cavity by the sole pushing effect of the concrete being cast thereinto. Rather, the need will arise for them to be mechanically removed from the cavity with the use of appropriate material removing equipment and machinery, which again entails a further increase in both production costs and time requirements. A further major drawback derives from the serious and - unfortunately - not uncommon possibility that, as the excavation work for forming the cavity for the secondary panel is being performed, the metal reinforcement of the adjacent primary panels previously formed is accidentally intercepted, thereby damaging the excavating means and tools and/or the same metal reinforcement of the panels; as it can be most readily appreciated, a panel having a damaged metal reinforcement is quite likely to prove detrimental not only to the actual strength of such panels in terms of adequately withstanding the dynamic and static stresses acting upon the foundation, but also to the water-tightness of the joints between the same panels. Still another drawback that is encountered with the afore-described method, notwithstanding the sophisticated sensing and control means and systems that are currently adopted, may derive from a possible misalignment of the excavation means relative to the primary panels, in particular when use is made of a ground borer or driller; in this way it may for instance quite easily occur that, as it moves down towards the bottom of the cavity to be formed, the borer removes increasingly larger portions of the flanks of a primary panel, while on the other hand leaving portions of soil, which should on the contrary be removed, in correspondence to the other primary panel on the opposite side. The economic damage and the loss of time incurred for restoring and plugging up the construction are most readily appreciable.

Another prior-art method consists in making the primary panels with the same method as described above, and then applying sheets of a metal material, commonly referred to as "sheet piles" in the art, to the flanks of the cavity being excavated, wherein these sheet piles are plunged into the bentonite prior to the concrete being cast into the cavity. Then, when the process is completed, the sheet piles are removed therefrom with the aid of special tools involving considerably high handling and operating costs, entailing an overall increase in the costs as well as delays in the building construction work. It is therefore an object of the present invention to do away with such drawbacks of prior-art methods and equipment, as they have been set forth hereinbefore, by providing a method and an apparatus for forming watertight panels in building foundations, special foundations, cutoff walls and similar constructions, which enable to obtain such panels in a more effective and quicker manner.

Within this general object, it is a purpose of the present invention to provide a method and an apparatus of the above-noted kind that are effective in enabling the panels to be laid down and set up in a precise, correct and accurate manner. A further purpose of the present invention is to provide a method and an apparatus of the above-noted kind, which are effective in doing totally away with or at least drastically reducing both the undesired removal of concrete from the flanks of the primary panels during the excavation of the soil for forming the secondary panels, and the serious risk to accidentally damage the strength-ensuring parts of the panels, such as the metal reinforcement. Yet another purpose of the present invention is to provide a method and an apparatus of the above-noted kind, which are effective in ensuring full and optimum water-tightness of the panels to effectively prevent water from seeping through the foundations in a long-term reliable manner. A further, equally important purpose of the present invention is to provide a method and an apparatus for forming watertight panels, which are economically competitive as compared with existing methods and equipment.

According to the present invention, the aims, purposes ad advantages set forth above, along with further ones that will become apparent from the following disclosure, are achieved by a method for forming watertight panels in building foundations, special foundations, cutoff walls and similar constructions, as defined in the appended claim 1 , as well as in an apparatus for carrying out such method as defined in the appended claim 8.

Further features and characteristics of the method and the apparatus for forming watertight panels according to the present invention are set forth and defined in the sub-claims.

Features and advantages of the present invention will anyway be more readily understood from the description of a particular, although not sole embodiment thereof that is given below by way of non-limiting example with reference to the accompanying drawings, in which:

- Figure 1 is a schematic view of a first working step for providing, with the aid of excavating means, such as a soil borer or driller, a cavity needed to set up foundations;

- Figure 2 is a schematic view of a second working step, in which the cavity shown in Figure 1 is filled with a material for stabilizing and temporarily filling the excavated cavity, such as bentonite or bentonite slurry;

- Figure 3 is a schematic view of a third working step, in which in the cavity shown in Figure 2 there are introduced a possible central reinforcement member immersed in the bentonite, and an apparatus for forming panels according to the present invention;

- Figure 4 is a schematic view of a fourth working step, in which the bentonite has been removed from the cavity and concrete has been cast thereinto;

- Figure 5 is a view of two contiguous primary panels provided according to the working steps shown in the preceding Figures, as viewed in a condition in which the apparatus according to the present invention has been removed therefrom;

- Figure 6 is a top plan view of a fifth working step, in which there are schematically illustrated the excavation means that are digging out a cavity being provided in a site located between the contiguous primary panels to accommodate a secondary panel therein;

- Figure 7 is a perspective view of the fifth working step represented in Figure 6;

- Figure 8 is a view similar to the one of Figure 6 of a sixth working step, in which in the cavity between the contiguous primary panels there has been introduced a stabilization and temporary-filling material, such as bentonite or bentonite slurry;

- Figure 9 is a perspective view of the sixth working step represented in Figure 8; - Figure 10 is a view of a possibly contemplated seventh working step of the method according to the present invention, in which in the cavity shown in the preceding Figures 8 and 9 there is fitted a possible reinforcement member immersed in the bentonite;

- Figure 11 is an enlarged view of a detail of Figure 10; - Figures 12, 13 and 14 are side, front and plan views, respectively, of an apparatus for forming watertight foundation panels according to the present invention;

- Figures 15 and 16 are views according to sectional plane l-l of Figure 14 and sectional plane M-Il of Figure 13, respectively; - Figures 17, 18 and 19 show, again according to the sectional plane M-Il of Figure 13, the apparatus of Figure 16 as broken down into modular elements;

- Figure 20 is a perspective view illustrating a portion of the apparatus shown in Figures 12 through to 19; - Figure 21 is a view of a sealing member associable to the apparatus shown in Figure 20;

- Figure 22 is a plan view of the apparatus shown in Figures 12 through to 20 in a first working condition thereof, as set up against the wall of a cavity intended for forming a primary panel; - Figures 23 and 24 are a same view as the one of Figure 22 and a perspective view, respectively, of the apparatus in a second working condition thereof;

- Figure 25 is a detail view of an inner portion of the apparatus shown in the preceding Figures;

- Figure 26 refers to a second embodiment of an apparatus for forming watertight foundation panels according to the present invention, shown in a perspective view;

- Figure 27 illustrates the apparatus of the preceding Figure from which the outer cover has been removed;

- Figures 28 and 29 show a detail of the apparatus of Figure 26 from which the upper cap has been removed and a sealing element is applicable thereto;

- Figure 30 is a section taken along sectional plane XXX-XXX of Figure 28; - Figures 31 and 32 show different operating configurations of the apparatus of Figure 26 according to a view similar to that of Figure 30;

- Figure 33 is a section taken along a medial longitudinal plane of a further embodiment of the apparatus according the present invention.

With reference to the above-listed Figures, schematically illustrated in Figures 1 to 5 there are the steps included in the method for forming watertight foundation panels according to the present invention. Specifically, as shown in Figure 1 , appropriate excavation means 1 remove the soil material 2 from the soil being excavated, thereby forming a cavity 3 having a substantially parallelepipedal shape; the excavation means 1 may be comprised of a special ground borer 1 or an excavating bucket, depending on the characteristics and the size of the cavity to be excavated, as well as on the nature of the soil material 2 to be removed.

There are of course provided the so-called sacrificial stringpieces, also referred to as horizontal stiffeners in the art, aimed at facilitating the formation of the cavity, although not shown in the Figures as they being widely and commonly known to all those skilled in the art.

Concurrently with the removal of the soil material 2 from the cavity 3, a material 4 aimed at stabilizing and temporarily filling the excavated portion is progressively poured into the same cavity 3 in order to prevent soil material 2 from possibly sliding down or coming off inside the cavity 3 as the latter is being excavated, since such occurrences would clearly prove prejudicial to the possibility for the excavation to be correctly carried out and completed; such stabilization and temporary-filling material 4 may be constituted by an inert material having a certain density, such as bentonite or a bentonite slurry. Schematically illustrated in Figure 2 is the cavity 3 as completed and filled with stabilization material 4.

Thereupon, as shown in Figure 3, one or more expandable apparatuses 5 for forming the so-called primary panels are introduced in the cavity 3 filled with stabilization material 3, along with the possibly provided metal members forming the reinforcement work 6. The metal members forming the reinforcement work 6, where provided, are generally fitted in the central region of the cavity 3, whereas the expandable apparatuses 5 for forming the panels are preferably placed against one or more walls of the same cavity 3 so as to delimitate such walls as concrete is cast into the cavity in a following step.

Each such expandable apparatus 5 comprises an expandable body 7, such as an inflatable air chamber or a similar variable-volume envelope of a floppy or elastically deformable material; this body 7 is furthermore removably provided with watertight coupling means, such as a sealing member 8 associated in correspondence to a seat 9 protruding relative to the surface of the body 7, as schematically illustrated in Figures 15 and 20; further features of the apparatus 5 shall anyway be described in greater detail further on.

The increase in volume of the expandable body 7 of the apparatus 5 is preferably carried out once the latter has been fitted into the cavity 3 duly filled with stabilization material 4, as shown in Figure 3.

Once the apparatuses 5 and, possibly, the reinforcement work 6 have been duly fitted in place, a casting of concrete 10 is done into the cavity 3, such concrete causing the stabilization material 4 to be removed from the same cavity. The thus cast concrete 10 will in this way form the so-called "primary" panel 11 , which is delimited on at least a flank, and preferably along two mutually opposite flanks, by the expandable apparatus 5, or expandable apparatuses 5, as the case may be, in the expanded state thereof, as shown in Figure 4. The cast concrete 10 also incorporates the sealing member 8 provided on each such expandable apparatus 5, which therefore is eventually integrated in the corresponding panel 11 upon conclusion of the concrete setting process, as shown in Figures 10 and 11. The concave shape of the sealing member 8 forms in this way a watertight coupling means between the primary panels 11 and the secondary panels that will subsequently be formed therebetween, further to acting as a guide for the excavation means 1 , as this shall be described in greater detail further on.

Once the concrete casting process is completed, the expandable apparatuses 5 are removed from the cavity 3 by appropriately reducing the volume of the expandable body 7, such as for instance through the deflation of the air chamber or through the retraction of the envelope forming the body 7, whereas the sealing member 8 remains incorporated in the panel 11. The removal of each such expandable apparatus 5 causes a hollow space 12 to be created between a flank of the panel 11 and the corresponding wall of the cavity 3.

The above-described process steps are repeated until the entire perimeter of the foundation is eventually defined with a sequence of "primary" panels having thus been formed in an arrangement in which they are spaced from each other by a distance that is roughly equal to the longitudinal extension thereof as measured along the perimeter of the foundation, as exemplified in Figure 5.

Once the sequence of primary panels has been thus defined, the process goes on with the formation of the secondary panels to be set up between each pair of contiguous primary panels. In this connection, and with reference to Figures 6 to 10, an excavation is performed in the soil 2 in order to form a cavity 3A between two contiguous primary panels 11 with the aid of the excavating means 1 (Figures 6 and 7); these excavating means are guided along the hollow spaces 12, by means of guide means generally known in the art or by the engagement of studs 13 provided on the excavating means 1 with a guide formed by the concavity of the sealing member 8, so as to remove the soil material between the primary panels 11 without having the cutting edges of the excavating means 1 coming into contact with the flanks of the same primary panels 11. In this way, the integrity of the concrete, which the panels 11 are formed of, is fully safeguarded.

In a manner similar to the one described afore in connection with the process of forming the cavities 3, a stabilization and temporary-filling material 4 is progressively filled into the cavity 3A during the excavation step performed to obtain said cavity 3A so as to prevent the soil material 2 from possibly subsiding and collapsing. Once the excavation in the soil 2 is completed, the resulting cavity 3A will therefore turn out as being full of such stabilization material 4, such as bentonite or bentonite slurry, as schematically illustrated in Figures 8 and 9. The process goes then further on with the possibly provided metal members forming the reinforcement work 6 being fitted in as already described hereinbefore and schematically illustrated in Figure 10, as well as with the concrete 10 being cast thereinto, wherein such concrete 10 - by conforming to the contact walls of the primary panels 11 - will form a male-kind joint to the concave contour of the sealing member 8 to thereby enable a watertight coupling of the same joint to be obtained, as clearly shown in Figure 11.

As already noted hereinbefore, the apparatus 5 for forming watertight foundation panels, illustrated in Figures 12 to 25, comprises an expandable body 7, such as an inflatable air chamber or a similar variable-volume envelope of a floppy or elastically deformable material, preferably shaped as a parallelepiped having a rectangular cross-section thereof; the expandable body 7 is further removably provided with watertight coupling means, such as a sealing member 8 associated to a seat 9 protruding relative to the surface of the body 7, as schematically illustrated in Figures 15 and 20; such seat 9 extends axially along one of the widest faces of the expandable body 7, preferably between the top edge and the bottom edge of the same body 7, wherein it protrudes from the latter with a substantially semi-cylindrical portion. The seat 9 comprises - in the central region thereof - retaining means, which may for example formed by a recess or slot 14, adapted to be engaged by corresponding engagement means provided on the sealing member 8 to removably connect the latter to the body 7, as illustrated in Figures 20 and 21.

The sealing member 8 comprises a connecting means 15, which is advantageously formed by a main body 15 shaped as a sector of a circular ring so as to be able to couple with the seat 9 by resting thereagainst. At the top of the arch there extends - perpendicularly to the main body 15 - a gripping or attachment member comprising a rectilinear portion 16 terminating with an enlarged portion 17 preferably having a substantially circular cross-section; this gripping or attachment member remains incorporated in the cast concrete 10 (see Figure 11 ), thereby firmly joining the sealing member 8 to the panel 11 and making it integral therewith.

Inside the body 7 there is fitted a metal pipe 18, from which there extends a plurality of interconnection members 19 between the same metal pipe 18 and the inner walls 20 of the body 7. The interconnection members 19, provided in a radial arrangement about the metal pipe 18 and preferably made in the form of flexible strips or bands, substantially function as tie rods for the body 7 and are fitted into appropriate slits 21 of the metal pipe 18 to be attached - at the ends thereof - to the inner walls 20 of the body 7. The purpose of the metal pipe 18 is to enable the expandable body 7 to achieve the expanded condition and the retracted condition: in the first case air is blown into the metal tube 18 to inflate the air bag or envelope making up the same body 7, while in the second case air is released by removing a plug or opening suitable valves provided in the metal pipe 18. The latter has also the task of facilitating the removal, or "dismantling" as this is often called in the technical jargon, of the apparatus 5 from the cavity 3: as schematically shown in Figures 22 to 25, after completing the deflating operation to bring the body 7 into the retracted state thereof, or concurrently with such operation, the metal pipe 18 is caused to rotate about its axis to thereby cause the interconnection members 19 to wind round the same metal pipe 18. This facilitates detaching the body 7 from the panel 11 and from the sealing member 8, which remains incorporated in the same panel 11 , as well as from the surrounding soil 2.

On the bottom of the expandable body 7 there will advantageously provided a pin 22 joining to the metal pipe 18, which allows for both correct positioning of the apparatus 5 in the cavity 3 and the possibility for the same apparatus 5 to oscillate such that its removal from the cavity 3, once that the panel 11 has been duly formed, is made easier.

Fully apparent from the above description is therefore the ability of the present invention to effectively reach the aims and advantages cited afore, by in fact providing a method and an apparatus for forming watertight panels in building foundations, special foundations, cutoff walls and similar constructions, which are effective in enabling foundation panels to be made in a much quicker and improved manner thanks to the provision of hollow spaces 12 resulting from the utilization of the expandable apparatus 5 inside the cavity 3; such hollow spaces in fact prevent the cutting tools of the excavating means 1 from coming into contact with the cast concrete 10 forming the primary panels 11.

In this way, the construction of the primary panels 11 , along with the excavating work done for forming the secondary panels, is much more accurate while the risk for concrete to be accidentally removed from the flanks of a primary panel 11 is practically avoided or, anyway, considerably reduced, under fully apparent advantages in terms of both time required to complete the works and construction costs.

In addition, incorporating the joining and sealing means, such as the afore- described watertight sealing member 8, into the structure of the primary panels 11 surely promotes to a further extent the cost-effectiveness of the method, as well as the easy and convenient manner in which it can be carried out, while at the same time ensuring an optimum, fully reliable and durable sealing effect against possible water seepages therethrough. It shall be appreciated that the method and apparatus for forming foundation panels as described above may be subject to a number of modifications and may be embodied in a number of different manners, or can be used in a number of different applications, without departing from the scope of the present invention as defined in claim 1. For instance, as this is exemplarily shown in Figures 17 to 19, instead of being made as a single-piece, unitary construction, the expandable apparatus 5 may comprise two or more modular elements 5A, 5B, 5C adapted to be appropriately connected operatively with each other, in order to make the transportation, handling and setting up at the building yard of the apparatus more convenient, in particular when significantly deep foundations have to be built.

Figures 26 to 33 disclose a second embodiment of an expandable apparatus 105 for the formation of watertight panels according to the present invention; the expandable apparatus 105 comprises an expandable body 107 formed by an outer envelope 123, preferably made of a floppy or elastically deformable material, which contains a plurality of first inflatable members 124 and second inflatable members 125, preferably having a tubular shape and made of an elastically deformable material such as, for instance, an elastomer. The first inflatable members 124 are advantageously arranged inside the outer envelope 123 so as to form one or more tube bundles, while the second inflatable members 125 are arranged outwardly and at opposite sides in respect to the tube bundles formed by the first inflatable members 124 so as to form a supporting surface for the outer envelope 123.

Further, at least a sealing member 108 is removably associable to the expandable body 107; the sealing member 108 is mountable in a seat 109 protruding in respect to the outer surface of the expandable body 107, as schematically represented in Figs. 28 and 29, respectively showing the condition preceding the mounting and the condition wherein mounting of the sealing member 108 into the seat 109 is completed. The seat 109 extends axially along one of the widest faces of the expandable body 107, preferably between the top edge and the bottom edge of the same body 107; the seat 109 can be made in one piece, or integrally, with the outer envelope 123 or it can be connectable to the same envelope through a process involving a physical and chemical joining such as, for instance, heat-sealing or welding. The seat 109 includes a pair of opposing walls 126, preferably elastically deformable, protruding from the outer envelope 123 with an arched profile; the opposing walls 126 form, at the top region, appropriate retaining means 114, constituted for instance by a recess perpendicularly arranged in respect to the expandable body 107, which are adapted to removably retain the sealing member 108 by means of corresponding connecting means 115, constituted by a first rectilinear portion engageable with the retaining means 114.

The sealing member 108 further includes a gripping member comprising a second rectilinear portion 116, arranged at an opposite side in respect to the first rectilinear portion 115, and an enlarged portion 117, preferably having a substantially circular cross-section, arranged between the first rectilinear portion 115 and the second rectilinear portion 116.

When mounted in the seat 109, the sealing member 108 extends perpendicularly to the expandable body 107; keeping in mind the method for forming the panels described hereinabove, when the apparatus 105 is removed from the cavity, the gripping member 116, 117 remains embedded in the panel formed by the concrete casting, thus rendering the sealing member 108 integral with the respective panel along a direction oriented parallel to the longitudinal extension of the same panel, that is transversely to the joint between two adjacent panels; in such a way the watertight seal of the joint so obtained is considerably enhanced.

A metal pipe 118 is arranged inside the expandable body 107; an interconnection member 119, preferably made as a flexible strap or band, is connected to the metal pipe 118. The interconnection member 119 at least partially surrounds the metal pipe 118, the first inflatable members 124 and the second inflatable members 125.

The purpose of the metal pipe 118 is to enable the expandable body 107 to achieve the expanded condition, when it is introduced inside the cavity, and the retracted condition, when the apparatus 105 has to be removed from the cavity after the concrete casting to form the primary panels has been completed. The first and the second inflatable members 124, 125 are inflated by flowing air in the pipe 118, thus expanding the expandable body 107, while the removal of a plug or opening suitable valves provided in the metal pipe 118 enables air to be released thus bringing the expandable body 107 in the retracted condition. The metal pipe 118, cooperating with the interconnection member 119, has also the task of facilitating the removal, or "dismantling" as this is often called in the technical jargon, of the apparatus 105 from the cavity. In fact, after completing the deflating operation to bring the expandable body 107 into the retracted condition, or concurrently with such operation, a rotational motion imposed to the metal pipe 118 about its axis causes the interconnection member 119 to wind around the same metal pipe 118, and therefore the retraction of the first and second inflatable members 124, 125 as a consequence of the compression applied on said inflatable members 124, 125 caused by the reduction in length of the interconnection member 119. This facilitates detaching the body 107 from the panel and from the sealing member 108 embedded in the panel.

In order to adjust the size of the apparatus 105 to the width of the cavity there are further provided adjusting members 127 transversely arranged inside the expandable body 107 by passing through respective guide channels 128 arranged between two adjacent first inflatable members 124 and communicating with the outside of the outer envelope 123. The use of such adjusting members 127, preferably made as a flexible strap, band or cable, is as follows: in the case when the width of the cavity to be formed is lower than the width of the apparatus 105, the adjusting members 127 are caused to pass through the respective guide channels 128 and around the second inflatable members 125, such that the second inflatable members are enclosed and tightened by the adjusting members 127 in the fully retracted position, as schematically shown in Figs. 31 and 32. In such a way, the air introduced inside the pipe 118 expands only the first inflatable members 124 and no one of the second inflatable members 125, or only the second inflatable members 125 located at one side of the first inflatable members 124, depending upon the width to be achieved in respect of the cavity.

Fig. 33 shows a further embodiment of an apparatus 205 according to the present invention, which comprises one or more expandable bodies 207A, 207B,

207C of the kind described hereinabove; the one or more expandable bodies 207A, 207B, 207C are adapted to be mutually interconnected in a modular manner, in order to make the transportation, handling and setting up at the building yard of the apparatus more convenient, in particular when significantly deep foundations have to be built.

It shall further be appreciated that the materials used, as well as the shape and the sizing of the various parts of the inventive tub assembly may each time be selected so as to more appropriately meet the particular requirements or suit the particular application.

Claims

1. Method for forming watertight panels in building foundations, special foundations, cutoff walls and similar constructions, comprising the steps of: a. forming a cavity (3) in the soil (2) having a substantially parallelepipedal shape by means of excavating means (1 ); b. concurrently with the removal of the soil material, progressively pouring a stabilization and temporary-filling material (4) into said cavity (3), characterized in that it further comprises the steps of: c. upon completing the excavation step, introducing in correspondence of at least a wall of said cavity (3) an expandable apparatus (5; 105; 205) delimiting said wall, said apparatus being brought to an expanded condition outside or inside said cavity (3); d. casting concrete (10) into the cavity (3) while concurrently removing said stabilization and temporary-filling material (4) therefrom, so as to form a first foundation panel (11 ); e. bringing said expandable apparatus (5; 105; 205) to a retracted condition and removing said apparatus (5; 105; 205) from said cavity (3) so as to obtain a hollow space (12) between a flank of said first panel (11 ) and said wall of said cavity (3).

2. Method according to claim 1 , wherein said expandable apparatus (5; 105; 205) is removably provided with watertight coupling means (8; 108).

3. Method according to claim 2, wherein said concrete (10) being cast in said cavity during said step (d) incorporates said watertight coupling means (8; 108).

4. Method according to claim 3, wherein in said step (e) said watertight coupling means (8; 108) remain incorporated in said first panel (11 ) when said apparatus (5; 105; 205) is removed from said cavity (3).

5. Method according to claim 1 , wherein said step (c) further provides for fitting a plurality of metal members constituting a metal reinforcement work (6) into a central region of said cavity (3).

6. Method according to any of the preceding claims, further comprising the steps of: f. forming a cavity (3A) in said soil (2) in a position contiguous to said first panel (11 ) by means of excavating means (1 ) duly guided along said hollow space (12); g. concurrently with the removal of the soil material, progressively pouring a stabilization and temporary-filling material (4) into said cavity (3A); h. casting concrete (10) into said cavity (3A) while concurrently removing said stabilization and temporary-filling material (4) therefrom, so as to form a second foundation panel coupled to said first panel (11 ) along said watertight coupling means (8; 108).

7. Method according to claim 6, wherein following said step (g) there is provided a step (g¹) in which a plurality of metal members constituting a metal reinforcement work (6) are fitted into a central region of said cavity (3A).

8. Apparatus for forming watertight panels in building foundations, special foundations, cutoff walls and similar constructions, characterized in that it comprises an expandable body (7; 107; 207A, 207B, 207C) adapted to be brought to an expanded condition to delimit at least a wall of a cavity (3) in the soil (2) for forming one of said panels (11 ), and a retracted condition so as to be removed from said cavity (3).

9. Apparatus according to claim 8, wherein watertight coupling means (8; 108) are removably associated to said expandable body (7; 107; 207A, 207B, 207C).

10. Apparatus according to claim 9, wherein said watertight coupling means (8; 108) are axially associable to a face of said expandable body (7; 107; 207A, 207B, 207C) in correspondence of a seat (9; 109) protruding from said expandable body (7; 107; 207A, 207B, 207C) and extending axially relative thereto.

11. Apparatus according to claim 10, wherein said seat (9; 109) comprises retaining means (14; 114) adapted to be removably engaged by corresponding connecting means (15; 115) provided on said watertight coupling means (8; 108).

12. Apparatus according to any of the claims 8 to 11 , wherein said watertight coupling means (8) comprise a sealing member including a main body (15) having a shape complementary to said seat (9), an attachment member (16, 17) adapted to be incorporated into said first panel (11 ) extending perpendicularly from said main body (15).

13. Apparatus according to claim 8, wherein said expandable body (7) comprises an inflatable air chamber.

14. Apparatus according to claim 8, wherein said expandable body (7) comprises a variable-volume envelope.

15. Apparatus according to any of the claims 8 to 14, wherein a metal pipe (18) is fitted inside said expandable body (7), a plurality of interconnection members

(19) extending between said metal pipe (18) and the inner walls (20) of said expandable body (7).

16. Apparatus according to claim 15, wherein said interconnection members (19) are provided in a radial arrangement about said metal pipe (18) and are attached to said inner walls (20) of said expandable body (7).

17. Apparatus according to claim 16, wherein said interconnection members (19) are constituted by flexible members such as strips, bands, or the like.

18. Apparatus according to claims 1 and 15, wherein said expanded condition of said expandable body (7) is obtained by blowing air into said metal tube (18), and said retracted condition of said expandable body (7) is obtained by releasing said air from said expandable body (7) via said metal pipe (18).

19. Apparatus according to claims 17 and 18, wherein a rotation of said metal pipe (18) about its axis causes said flexible interconnection members (19) to wind round said metal pipe (18) when said expandable body moves from said expanded condition to said retracted condition, or when the retracting operation is completed.

20. Apparatus according to any of the claims 8 to 19, characterized in that it comprises two or more modular elements (5A, 5B, 5C) adapted to be mutually interconnected.

21. Apparatus according to any of the preceding claims, characterized in that it comprises and expandable body (107; 207A, 207B, 207C) formed by an outer envelope (123) containing a plurality of first inflatable members (124) and second inflatable members (125).

22. Apparatus according to claim 21 , wherein said first inflatable members (124) and said second inflatable members (125) have a tubular shape, said first inflatable members (124) being arranged inside said outer envelope (123) so as to form one or more tube bundles, said second inflatable members (125) being arranged outwardly and at opposite sides in respect to said tube bundles so as to form a supporting surface for said outer envelope (123).

23. Apparatus according to claims 21 or 22, wherein at least a sealing member (108) is removably associable to said expandable body (107), said sealing member (108) being mountable in a seat (109) protruding and axially extending in respect to an outer surface of said expandable body (107).

24. Apparatus according to claim 23, wherein said seat (109) includes a pair of opposing walls (126) provided with retaining means (114) adapted to removably retain said sealing member (108).

25. Apparatus according to claim 24, wherein said sealing member (108) is provided with connecting means (115) engageable with said retaining means (114).

26. Apparatus according to claim 25, wherein said sealing member (108) extends perpendicularly to said expandable body (107) when mounted in said seat (109).

27. Apparatus according to any of claims 21 to 26, comprising a metal pipe (118) arranged inside said expandable body (107), at least an interconnection member (119) at least partially surrounding said metal pipe (118), said first inflatable members (124) and said second inflatable members (125) being connected to said metal pipe (118).

28. Apparatus according to claim 27, wherein a rotational motion imposed to said metal pipe (118) about its axis causes said interconnection member (119) to wind around said metal pipe (118) and, as a consequence, the retraction of said first inflatable members (124) and said second inflatable members (125).

29. Apparatus according to any of claims 21 to 28, comprising adjusting members (127) to adjust the width of said apparatus (105), said adjusting members (127) being transversely arranged inside said expandable body (107) by passing through respective guide channels (128) arranged between two adjacent first inflatable members (124), said guide channels (128) being in communication with the outside of said outer envelope (123).

30. Apparatus according to claim 29, wherein said adjusting elements (127) are adapted to enclose and tighten in a fully retracted position said second inflatable members (125).