WO2010150253A2

WO2010150253A2 - Device, system and method for protection of structural elements against soil forces

Info

Publication number: WO2010150253A2
Application number: PCT/IL2010/000497
Authority: WO
Inventors: Basem Hazzan
Original assignee: Basem Hazzan
Priority date: 2009-06-24
Filing date: 2010-06-23
Publication date: 2010-12-29
Also published as: WO2010150253A3

Abstract

A device, system and method for protection of concrete elements against soil forces. The system comprises two slabs made of a compressible material. The slabs are vertically standing and facing inner sides of each other. Each of the inner sides comprises a wedge having a bearing surface in an upper portion thereof. A horizontal slab is mounted on the bearing surfaces. When the concrete is poured, it is bounded by an upper face of the horizontal slab and by the inner sides of the vertical standing slabs. Thus, a large void is formed between the concrete and the ground and swelling soil may fill this void without affecting the concrete element of above.

Description

DEVICE, SYSTEM AND METHOD FOR PROTECTION OF STRUCTURAL ELEMENTS AGAINST SOIL FORCES

FIELD OF THE INVENTION The present invention relates to the field of devices, systems and methods for the lowering or elimination of forces caused by soil swelling or movement, regardless of their direction, acting on structural elements like concrete beams, walls, plates and the like that are in contact with swelling or moving soils such as clay or the like.

BACKGROUND OF THE INVENTION

Certain types of soils, such as clay and marl, swell and shrink when they absorb or exude water. Water is usually absorbed by soils during the rainy season, by irrigation, by accidental or intentional water spillage and the like, and is typically exuded by seepage or evaporation during the dry season.

In soil engineering, movement of water in soils is often a critical problem in building foundations. Seepage depends on several factors, including permeability of the soil and the pressure gradient, essentially the combination of forces acting on water through gravity and other factors. Permeability can vary over a wide range, depending on soil structure and composition.

The soil shrinkage and swelling lead to substantial horizontal and vertical soil movements which cause significant forces to act on structural elements which are in contact with such soils, as is known. The heave forces caused by the swelling of the soil, as well as other forces caused by movement of the soil will be called hereinbelow "soil forces". Typically, the majority of the soil forces are related to heave forces.

The soil forces may bend, shear and tilt the structural elements acted upon, thus often damaging them and any structures or elements connected to them. Swelling movements and the forces caused by them are, according to the present state of the art, difficult to estimate or to avoid. As a result, there is often a requirement to create and maintain a gap or a void between such structural elements and the soil, to prevent these forces from acting on and reaching said elements. At some cases, a gap between the structural elements and the soil is formed by placing a relatively easily compressible material inbetween. Such a material may be, for example, foamed polystyrene (Styrofoam ®). However, soil movements, especially vertical movements of the soil as a result of heave forces, may raise the compressible material, that, even if somewhat compressed, may induce vertical forces upon the structural elements, and, eventually, leads to their displacement and damaging.

Furthermore, typical blocks of foamed polystyrene found in the market are produced with a void at their lower portion. Such voids usually have a height of 20 cm. In a case of swelling soil, the soil may fill the entire void of each block thereby rendering useless its design to keep the soil away from the structural elements.

At other cases, the structural elements are constructed over filled soil and not clay. However, if a clay layer is found under the filled soil, swelling of the clay may lead to upward displacement of the filled soil and damaging of the structural elements

Typically, the problems caused by soil movement relate to vertical movements of the soil. However, horizontal movements of the soil may negatively affect structural elements as well.

Another problem that often occurs during construction works is the collapse of trench walls and its negative effect on the beams and other structural elements. Such a collapse may occur with various types of soils before, during and after the casting of the concrete elements. Thus, such a collapse may partly of fully fill with collapsed soil any gaps and voids required by the designer, and therefore may cause unplanned soil forces to act on elements or beams and the like that are in contact with the collapsed soil.

Known methods of using polystyrene for casting of concrete elements comprise using a polystyrene block having a "U" shape which is divided into several U-shape voids. The block is placed on the ground with its open side facing downward and its closed side facing upward. The width of the block is typically limited to 20 cm. The thickness of its upper portion is typically 1.5 cm. The sides of the "U" are converging downwardly such that their upper portion, adjacent the block upper portion, has a width of 2.5 cm and their lower tipped portion that stands on the ground has a width of 0.8 cm. Flat polystyrene slabs are placed vertically at each side of the upper portion of the U-shaped block. A reinforcement construction is built on each side of the block in order to support the polystyrene slabs. Then, a reinforcement steel construction is placed on the block and concrete is poured between the block and the vertical standing slabs.

The method described above suffers from several disadvantages: a. The width of the U-shaped block is limited to 20 cm. Therefore, if other widths are necessary, a use of polystyrene block with such a method cannot be efficiently implemented. b. The height of the U-shaped block is limited to 25 cm. Therefore, if other heights are necessary, a use of a polystyrene block with such a method cannot be efficiently implemented. c. After the casting stage, when filling with filled soil against the U-shaped blocks, a protection board is usually placed between the soil and the "legs" of the "U" block in order to prevent their breakage due to the soil pressure, since such a breakage will permit entrance of soil under the casted element, in contrary to the design. d. In any case, the "legs" of the "U" block remain in contact with the soil. Thus, in a case of heave forces produced by the ground, even if the "U" block is somewhat compressed, still the soil pressure may reach the concrete element and cause it damage.

It is the object of the present invention to provide a device, system and method that significantly reduces or overcomes the aforementioned disadvantages.

It is a further object of the present invention to provide an effective, inexpensive and easy to implement device, system and method to protect structural elements against soil forces.

It is still a further object of the present invention to provide a device, system and method that reduces passage of moisture from the ground to the structural elements.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided a device for protection of a concrete element against soil forces created due to soil movement, the device comprising: a slab made of a compressible material having a slab inner side and a slab outer side; wherein: the slab inner side faces the concrete element; and the slab outer side faces the soil. Typically, the slab is mounted vertically; and a lower portion of the slab comprises a wedge that is wedge-shaped.

Advantageously, an upper portion of the wedge comprising a bearing surface that is substantially horizontally directed.

In some embodiments, the wedge is double-sided; and the upper portion of the wedge comprising a plurality of bearing surfaces that are located on opposite sides of a symmetry plane of the device. In some embodiments, an upwardly extending protrusion extends between the bearing surfaces.

If desired, a vertical splitting element is located at a lower portion of the device; a lower portion of the vertical splitting element is in contact with the ground; and an upper portion of the vertical splitting device converges upwardly and is in contact with the lower portion of the device.

Advantageously according to the present invention, two slabs having bearing surfaces are facing each other with their inner surfaces; and a horizontal slab rests between the two bearing surfaces. If desired, a lower portion of the device comprises a cutting element. Typically, the cutting element comprises a wire.

In use in some embodiments, the cutting element constitutes a horizontal cutting element.

Further in accordance with the present invention there is provided a system for the protection of a concrete element against soil forces, the system comprising: two slabs made of a compressible material and having a slab inner face and a slab outer face, the slabs are vertically standing and facing each other with their inner faces, each of the inner faces comprises a wedge, an upper portion of the wedge constituting a bearing surface; a substantially horizontal slab mounted on the bearing surfaces of two standing vertical slabs; and the concrete element lies above the horizontally mounted slab. Typically, the concrete element is bounded by the horizontal slab at a lower side of the concrete element, and by the inner faces of the vertical slabs at peripheral sides of the concrete element. Still further in accordance with the present invention there is provided a method for the protection of a concrete element against soil forces, the method comprising the steps of: a - providing two slabs made of a compressible material, each of the slabs has an inner face and an outer face, a lower portion of the inner face comprising a downwardly directed wedge that ends with an horizontal bearing surface at an upper portion of the wedge, b - positioning the slabs vertically with their inner faces facing each other, c - positioning an horizontal slab made of a compressible material on the bearing surfaces of the two vertical slabs, d - placing a structure of steel reinforcement of the concrete element on the horizontal slab, and e - pouring concrete on the horizontal slab so as to cover at least a portion of the steel reinforcement. Generally, the poured concrete is bounded by the vertically standing slabs.

If desired, at least some of the vertical standing slabs are attached one to the other at their outer faces.

In some embodiments, the method further comprising the steps of: f - installing a cutting element at least around some of the vertical slabs; and g - horizontal cutting of at least some of the vertical slabs by the cutting element upon final hardening of the poured concrete.

If desired, the method further comprising the step of installing a vertical splitting element under at least some of the vertical standing slabs.

According to some embodiments, the slab outer side is connected to an external layer made of one or a combination from a group consisting of: a - a relatively rigid plate, b - a bituminous material, c - a plastic sheet, d - an expanded net. If desired, the external layer covers an entire periphery of the slab. Advantageously, the use of a device according to the present invention may assist in preventing moisture from the ground from getting to the concrete element, for example, a connecting beam, since the beam is covered at its bottom and its sides with the mold made of the slabs that are moisture repellant. Another advantage of the device is that during a casting of concrete elements, including beams and floor, it is possible to raise the external basic elements several centimeters, e.g., 10 cm, above the planned level of the casted floor in order to prevent penetration of moisture between the floor and the first level of blocks that will be built upon. Therefore, the use of the device, system and method according to the present invention is also advantageous in non- swelling soils.

Generally, the separation of structural elements, like beams or floor, from the ground, by means of the device according to the present invention, may prevent moisture from the ground from entering into those elements.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention and to show how the same may be carried out in practice, reference will now be made to the accompanying drawings, in which: Fig. 1 is a sectional view of a basic element according to the present invention;

Fig. 2 is a sectional view of a device according to the present invention using the basic element of Fig. 1;

Fig. 3 is a sectional view of another embodiment of a device according to the present invention using the basic element of Fig. 1 ;

Fig. 4 is a perspective view of a line vertical support element using the basic element of Fig. 1;

Fig. 5 is a perspective view of a point vertical support element using the basic element of Fig. 1; Fig. 6 is a perspective view of a vertical splitting element;

Fig. 7 is a perspective view of a cutting element; Fig. 8 is a perspective view of the cutting element of Fig. 7 shown in a position to cut a line support element; and

Fig. 9 is a cross-sectional view of a slab provided with an external layer

DESCRIPTION OF PREFERRED EMBODIMENTS

Attention is first drawn to Figs. 1 to 5 that show a device 10 for protection of a concrete element against soil forces according to the present invention. As shown, the device 10 comprises a basic element 12 made of a compressible material. A preferred material for the basic element 12 is polystyrene due to its various advantages comparing to other construction materials. Such advantages may be, for example, low price, low weight, high insulation, high permeability, easy to cut, easy to apply, and relatively high strength to weight ratio. Despite the choose of polystyrene as a preferred material for the basic element 12, it is noted that other construction materials, e.g., plastic, may be chosen as well, provided that they may be suitable to the functionality of the device 10.

The basic element 12 is in the form of a slab 14 having a slab inner side 16 and a slab outer side 18. The slab 14 has a slab upper portion 20 and a slab lower portion 22. At the slab outer side 18, the slab upper portion 20 merges with the slab lower portion 22 in the form of an outer flat face 24.

At the slab inner side 16, the slab upper portion 20 is formed as an inner flat face 26. The slab lower portion 22 comprises a wedge 28 that is wedge- shaped toward a slab lower end 30. An upper portion 32 of the wedge 28 comprises a bearing surface 34. In use of the basic element 12, it is typically mounted vertically and the bearing surface 34 is substantially horizontally directed.

It should be noted that directional terms appearing throughout the specification and claims, e.g. "forward", "rear", "upper", "lower" etc., are used as terms of convenience to distinguish the location of various surfaces relative to each other. These terms are defined with reference to the figures, however, they are used for illustrative purposes only, and are not intended to limit the scope of the appended claims.

In use of the device 10 for casting a concrete beam 36, two basic elements 12 are placed vertically opposite each other at a first distance Dl between their inner flat faces 26. The first distance Dl can be easily amended according to the required width W of the beam 36 that should be casted.

Typically, the width W of a beam 36 is in the range from 20 cm to 40 cm, however, it is an advantage of the present invention that the first distance Dl may be chosen to be any required value, practically, up to 100 cm or even more.

The basic elements 12 are placed such that their slab inner sides 16 face each other, and, hence, also the bearing surfaces 34 face each other. A horizontal slab 40, having a horizontal slab upper face 42 and a horizontal slab lower face 44, is placed on the two oppositely facing bearing surfaces 34.

Thus, a mold 46 for casting concrete 48 is formed between the horizontal slab upper face 42 and the two inner flat faces 26 of the basic elements 12. At this stage, wooden support structure (not shown) may be temporarily built at the sides of the mold for supporting the basic elements 12 during the casting and the drying of the concrete 48.

In case of a varying level of the ground G, or, if it is desired to provide a different height of the position of the horizontal slab 40, the wedge 28 of any basic element 12 may be cut by a knife to the desired height.

When several basic elements 12 had to be attached in line, in order to form a long mold 46, an end face 38 of one basic element 12 is connected to the end face 38 of the consecutive basic element 12 simply by applying silicone between the end faces 38, or any other appropriate glue or connecting substance.

Before casting, a steel reinforcement 50 of the beam 36 is placed in the mold 46. Typically, the steel reinforcement 50 is spaced from the horizontal slab upper face 42 and from the two inner flat faces 26 of the basic elements 12 by spacing means as known in the art. The spacing means (not shown in the drawings) may be, for example, plastic spacers that are attached to the steel reinforcement 50 and assure that during the casting the steel reinforcement 50 will not reach the periphery of the beam 36, i.e., neither the horizontal slab upper face 42 nor the two inner flat faces 26 of the basic elements 12.

Hence, the device 12 enables to perform a fast, efficient and economical casting of a concrete element, for example, a beam 36. Due to the construction of the device 10, neither of the basic elements 12 nor the horizontal slab 40 has to be dismantled after the drying and curing of the concrete 48. After the casting had ended, fill soil 52 is filled, if necessary, at a side of the beam 36. The filling of the fill soil 52 may take place without the necessity of further steps to be taken. Thus, the beam 36 remains protected from the fill soil 52 by the protection of a basic element 12. Furthermore, the beam 36 remains protected from soil forces by the fact that it is well spaced from the soil below due to a large void 54 created between the horizontal slab 40 and the ground G, and, in a case of swelling of the soil below, it may enter the large void 54 without reaching or affecting the beam 36.

In a case where it is necessary to cast a wide and flat concrete element, for example, a floor 56 between two beams 36, typically further vertical support elements 58 should be provided between the two beams 36. In that case, the vertical support elements 58 may be made by using the same basic element 12 as used for casting the beam 36. In order to provide a vertical support element 58, as shown in Fig. 3, a fast and simple process involves the step of providing two basic elements 12 and connecting them, one to the other, at their outer flat faces 24. The connection may take place by any appropriate manner as known in the art. According to some embodiments, the basic elements 12 are connected to each other by means of silicone.

At the next step, any surplus height above the wedge 28 may be cut away in a simple manner, for example, by a knife. Thus, eventually, a vertical support element 58 has a shape as shown in the figures, and having a wedge- shape from both sides, i.e., a double wedge shape with respect to a vertical symmetry plane P, and horizontal support surfaces 60 at both sides of the symmetry plane P. Typically the vertical support element 58 is further provided with an upwardly extending protrusion 62 between the two horizontal support surfaces 60. The vertical support element 58 may be constructed at two main options, depending on the vertical support required for each case. Thus, the vertical support element 58 may be made as a line vertical support element 64 or as a point vertical support element 66. The point vertical support element 66 may be produced from a line vertical support element 64 that is cut into thin slices. In use, any combination of line vertical support elements 64 or point vertical support elements 66 may be used.

In the case of the casting described above, i.e., casting a floor 56 together with a beam 36, it may be advantageous to first cast partially the beam 36 up to a lower level 67 of the floor 56 and then, at a second stage, cast the remaining portion of the beam 36 together with the floor 56. This method enables the steel reinforcement 50 of the beam 36 to be casted integrally with the steel reinforcement 50 of the floor, thus providing an homogenous and strong casting of the beam 36 together with the floor 56.

In a case where it is desired to prevent any possibility that heave forces

68 acting upwardly will raise the vertical support element 58, or the basic element 12, and, thus, negatively affect the concrete element, even if a contact area 70 of the vertical support element 58 with the ground G is relatively small, typically, at a width of 3 to 5 cm, a vertical splitting element 72 is located at a support bottom 74. According to some embodiments, the vertical splitting element 72 comprises a base 76 and an upwardly converging body 78 ending with a sharp edge 80 at a body upper portion 82 (see Fig. 6).

In use of the vertical splitting element 72, its base 76 is placed on the ground G under the vertical support element 58 and its sharp edge 80 is slightly inserted into the contact area 70 of the vertical support element 58 with the ground G. In a case that the vertical support element 58 is subjected to heave forces or the like acting vertically upon, the swelling of the ground G will push upwardly the base 76 of the vertical splitting element 72, and the sharp edge 80 will further penetrate into the vertical support element 58. Eventually, if the penetration will be large enough, the vertical support element 58 will no longer be able to withstand its widening by the body 78 of the vertical splitting element 72 and it will open apart into two sections and collapse, thus losing any contact with the ground G. In this case, further swelling of the soil will not be able to push vertically the collapsed vertical support element 58, thus, the concrete element located above the vertical support element 58 will remain without any contact with the swelling soil.

In a further case where it is desired to prevent any possibility that heave forces 68 acting upwardly will raise the b asic elements 12 or the vertical support elements 58, and, thus, negatively affect the concrete element, according to some embodiments the present invention is provided with a cutting element 84, as shown in Fig. 7, for cutting the vertical support elements 58, and, if desired, also for cutting the inner basic elements 12 that are remote from the fill soil 52, thus completely separating between the concrete elements and the ground G.

Typically, as shown in Fig. 8, the cutting element 84 is horizontally installed and it comprises a wire 86 that is put around any desired basic element 12 or vertical support element 58 prior to the casting, with one or two ends 88 of the wire 86 within a reach of hand. After the casting, and upon the curing of the concrete, when it is desired to completely separate a specific concrete element from the ground G, the associated wire 86 is pulled in a cutting direction 98 that is suitable for the given element, thus tearing apart the lower portions of either the basic elements 12 or the vertical support elements 58. The cutting direction 98 does not have to be directed as shown in Fig. 8 with respect to the vertical support element 64, i.e., along a longitudinal direction of the vertical support element 64, and other cutting directions may be chosen as well, for example, perpendicular to the cutting direction 98 as shown, or any combination of directions inbetween.

In some embodiments of the cutting element 84, when it is desired to completely destroy the wedge 28 of the basic element 12 or of the vertical support element 58, a farthest portion of the wire 86 that is found innermost under the cast elements and farthest from the free ends 88 of the wire 86, is provided with a tearing element 90 or the like. The tearing element 90 may be in the form of any volumetric body that is suitable for tearing apart the associated elements upon being forcibly pulled by the wire 86. If the associated elements are torn apart, it is guaranteed that no part of an element may rest on another part of an element, and therefore, there will not be a continuous contact between the ground G to the concrete element through an inner basic element 12 or a vertical support element 58.

Thus, in a very simple and economical manner, the concrete elements may be produced completely separated from the ground G, thus eliminating any possibility of negatively affecting concrete elements by soil forces.

In some cases, it is desired to provide the compressible slabs with an extra protection to its outer side. The extra protection may provide the slabs with the following improvements; increased toughness, increased hardness, increased abrasive resistance, increased tearing resistance, increased permeability. Thus, an outer side 92 of a slab 94, as shown in Fig. 9, may be further provided with an external layer 96 made of one or a combination from a group consisting of; a relatively rigid plate, a bituminous material, a plastic sheet, and an expanded net.

The external layer 96 of any slab 94 may be form according to specific needs of the slab 94. Thus, for example, the external layer 96 may be formed at one side only of the slab 94, as shown in Fig. 9, at two sides of the slab 94, or it may even cover the entire envelope of the slab 94. Thus, according to the described above, the device, system and method according to the present invention embodies the following advantages: a. The time required for the installation of the present device is considerable shorter than the time required at present for the installation of similar systems as known in the art, since wooden moldings and their reinforcement structure do not have to be built. b. A lot of material is saved due to the fact that wooden moldings and their reinforcement structure are no longer necessary. c. No material is getting lost like in present systems where the wooden molding is left under the castings since it cannot be taken away. d. The void under the casted element can be made at any desired height and is not limited to the height of present standard polystyrene blocks which is 20 or 25 cm. e. The casting may be done at any desired width. f. No sealing of the concrete elements is necessary since the polystyrene slabs protect the concrete elements up to above the final ground G level that is obtained after development of the ground G.

Although the present invention has been described to a certain degree of particularity, it should be understood that various alterations and modifications could be made without departing from the spirit or scope of the invention as hereinafter claimed.

Claims

CLAIMS:

1. A device (10) for protection of a concrete element against soil forces created due to soil movement, the device comprising: a slab (12, 14) made of a compressible material having a slab inner side (16) and a slab outer side ( 18); wherein: the slab inner side (16) faces the concrete element; and the slab outer side (18) faces the soil.

2. The device (10) according to claim 1, wherein: the slab (12) is mounted vertically; and a lower portion (22) of the slab comprises a wedge (28) that is wedge- shaped.

3. The device (10) according to claim 2, wherein: an upper portion (32) of the wedge (28) comprising a bearing surface

(34) that is substantially horizontally directed.

4. The device (10) according to claim 3, wherein: the wedge (28) is double-sided; and the upper portion (32) of the wedge comprising a plurality of support surfaces (60) that are located on opposite sides of a symmetry plane (P) of the device.

5. The device (10) according to claim 4, wherein: an upwardly extending protrusion (62) extends between the bearing surfaces.

6. The device (10) according to claim 4, wherein: a vertical splitting element (72) is located at a lower portion of the device; a lower portion of the vertical splitting element is in contact with the ground (G); and an upper portion (82) of the vertical splitting element converges upwardly and is in contact with the lower portion of the device.

7. The device (10) according to claim 3, wherein: two slabs (12) having bearing surfaces (34) are facing each other with their inner sides (16); and a horizontal slab (40) rests between the two bearing surfaces.

8. The device (10) according to claim 2, wherein: a lower portion of the device comprises a cutting element (84).

9. The device (10) according to claim 8, wherein: the cutting element (84) comprises a wire (86).

10. The device (10) according to claim 8, wherein: the cutting element (84) constitutes a horizontal cutting element.

11. A s ystem for the protection of a concrete element against soil forces, the system comprising: two slabs (12) made of a compressible material and having a slab inner side (16) and a slab outer side (18), the slabs are vertically standing and facing each other with their inner sides (16), each of the inner sides comprises a wedge (28), an upper portion of the wedge constituting a bearing surface (34); a substantially horizontal slab (40) mounted on the bearing surfaces of two standing vertical slabs; and the concrete element lies above the horizontally mounted slab.

12. The s ystem according to claim 11, wherein: the concrete element is bounded by the horizontal slab (40) at a lower side of the concrete element, and by the inner sides (16) of the vertical slabs (12) at peripheral sides of the concrete element.

13. A method for the protection of a concrete element against soil forces, the method comprising the steps of: a - providing two slabs (12) made of a compressible material, each of the slabs has an inner side (16) and an outer side (18), a lower portion of the inner side comprising a downwardly directed wedge (28) that ends with an horizontal bearing surface (34) at an upper portion (32) of the wedge, b - positioning the slabs (12) vertically with their inner sides (16) facing each other, c - positioning an horizontal slab (40) made of a compressible material on the bearing surfaces of the two vertical slabs, d - placing a structure of steel reinforcement (50) of the concrete element on the horizontal slab, and e - pouring concrete (48) on the horizontal slab so as to cover at least a portion of the steel reinforcement.

14. The method according to claim 13, wherein: the poured concrete (48) is bounded by the vertically standing slabs (12).

15. The method according to claim 13, wherein: at least some of the vertical standing slabs (12) are attached one to the other at their outer sides (18) thus forming vertical support elements (58).

16. The method according to claim 15, further comprising the steps of: f - installing a cutting element (84) at least around some of the vertical slabs (12, 58); and g - horizontal cutting of at least some of the vertical slabs by the cutting element upon final hardening of the poured concrete.

17. The method according to claim 15, further comprising the step of installing a vertical splitting element (72) under at least some of the vertical standing slabs (12, 58).

18. The device ac cording to claim 1, wherein; the slab (14) is connected to an external layer (96) made of one or a combination from a group consisting of: a - a relatively rigid plate, b - a bituminous material, c - a plastic sheet, d - an expanded net.

19. The device ac cording to claim 18, wherein: the external layer (96) covers an entire periphery of the slab.