A strut structure for a construction pit and a method for locking the strut structure

Abstract

A strut structure for a construction pit comprises two upright walls, and a jack and an elongated strut arranged in series therebetween. The jack is extendable from an initial condition to an extended condition and lockable in the extended condition. The strut structure is further provided with a closable reservoir for receiving a substantially incompressible and liquid medium. The reservoir is arranged between one of the walls and the strut. At least in an empty condition of the reservoir the length of the reservoir is variable in longitudinal direction of the strut.

Description

[0001] The present invention is related to a strut structure for a construction pit, comprising two upright walls, and a jack and an elongated strut arranged in series therebetween, wherein the jack is extendable from an initial condition to an extended condition and lockable in the extended condition.

[0002] Such a strut structure is known in the prior art and is applied for creating a construction pit, for example, wherein the two upright walls may be two opposite retaining walls. The strut and the jack may be located between the retaining walls and keep them at fixed mutual positions. During building the strut structure the retaining walls, after inserting them into the ground, are pushed away from each other by moving the jack from the initial condition to the extended condition thereof. Consequently, the whole structure is prestressed, such that soil setting at outer sides of the retaining walls is avoided after removing soil from between the retaining walls. The jack is locked in the extended condition, such that it is not necessary to control it continuously. Subsequently, the soil between the retaining walls can be removed for creating the construction pit. A force which is applied onto the jack and the strut may increase strongly, in practice up to 1500 ton, for example. The prestress upon initially pushing the retaining walls from each other is usually only 10-20% of the final force after creating the construction pit.

[0003] After finishing building work the strut and the jack may be removed by eliminating pressure force on the strut. If the jack is locked through a securing it appears difficult in practice to remove the securing due to the high force. In that case the force is eliminated, for example, by cutting the strut, which is usually made of steel, by means of a cutting torch.

[0004] An object of the invention is to provide a strut structure for simply dismantling the strut and the jack with respect to the upright walls.

[0005] This object is achieved with the strut structure according to the invention, wherein the strut structure is further provided with a closable reservoir for receiving a substantially incompressible and liquid medium, which reservoir is arranged between one of the walls and the strut, wherein at least in an empty condition of the reservoir the length of the reservoir is variable in longitudinal direction of the strut.

[0006] The strut structure according to the invention provides the possibility to fill the reservoir with incompressible and liquid medium, for example dry sand, during building it, and subsequently closing the reservoir and push the upright walls away from each other by means of the jack, such that the walls together with the strut, the jack and the reservoir are prestressed. Subsequently, the jack can be locked in the extended condition, such that the mutual positions of the retaining walls can be maintained. Then, the soil between the retaining walls can be removed which leads to an increased force onto the jack and the strut. For dismantling the strut structure the reservoir can be opened to remove the liquid medium from it, such that the reservoir can be reduced in longitudinal direction of the strut due to the variable length in its empty condition. This means that it is no longer necessary to control the jack in order to eliminate stress on the strut. Therefore, an advantage of the invention is that the strut, the jack and the reservoir can be decoupled in a simple manner.

[0007] The reservoir can be adapted such that the incompressible and liquid medium is discharged automatically upon opening the closable opening. This can be achieved by providing the lower side with a closable seal, for example.

[0008] If the medium is not fully incompressible, the length of the reservoir will be shortened in longitudinal direction of the strut in a limited way during pushing the walls away from each other in order to somewhat compress the medium.

[0009] A further advantage of the variable length of the reservoir is that the stroke of the strut may be relatively short by adapting the length of the reservoir in longitudinal direction of the strut accordingly. This provides the opportunity to apply a relatively simple and low-cost jack.

[0010] The jack and the reservoir may be located in alignment with the strut.

[0011] For example, the jack is located between the reservoir and the strut, but it is also possible that the reservoir is located between the reservoir strut and the jack.

[0012] In a particular embodiment the jack comprises a space which is expandable in longitudinal direction of the strut, wherein the space includes an enclosure, which is provided with a connection for supplying a medium at elevated pressure into the space.

[0013] The enclosure may be provided with two opposite side walls which extend transversely to the longitudinal direction of the strut and are movable relative to each other in longitudinal direction of the strut. Preferably, the side walls are movable with respect to each other such that an angle between them stays the same, for example parallel to each other.

[0014] In order to absorb high loads the side walls may be rigid, for example in the form of steel plates.

[0015] It is also possible that the side walls are flexible. In that case the flexible side walls abut rigid elements, such as steel plates.

[0016] The side walls may be connected to each other by a flexible wall, which together with the side walls, enclose the space, for example a tubular bellow or a rubber ring.

[0017] In a particular embodiment the flexible wall has an accordion shape.

[0018] In a preferred embodiment the side walls are flexible and connected to each other by a flexible wall, which together with the side walls encloses the space, wherein the side walls and the flexible wall are made in one piece, for example through an injection moulding process.

[0019] The jack can be lockable in the extended condition by introducing a curable material into the expandable space. In this case one may think of grout. If after achieving a desired pressure the material is cured, the jack is locked in the extended condition of the walls. In fact, the cured material forms a securing of the jack.

[0020] Preferably, the reservoir has a housing including a wall which is movable in the longitudinal direction of the strut. This means that the length of the reservoir can be varied in a simple manner.

[0021] When the movable wall is adjacent to or coincides with one of the side walls of the jack, a compact structure is realized.

[0022] In a practical embodiment the housing of the reservoir comprises a tube including the movable wall therein and in which the jack is also located. The tube may have a fixed closure at one side thereof and variable closure at the other side thereof, which variable closure comprises the variable wall.

[0023] The flexible wall of the jack may abut the tube in the extended condition of the jack. In that case, the flexible wall may also form a closure against leakage of the incompressible medium in the reservoir through a possible opening between the tube and one of the sidewalls of the jack which comprises the movable wall of the reservoir.

[0024] Th reservoir and the jack together may form one pressure body which is located between the strut and one of the upright walls.

[0025] The invention is also related to a method for locking the strut structure as described hereinbefore, comprising the following sequential steps: placing the jack in its initial condition, the strut and the reservoir in series behind each other between the upright walls, filling the reservoir with an incompressible and liquid medium, like dry sand, filling the jack with a curable medium, like grout, such that the jack is extended from the initial condition to the extended condition, and curing the curable medium. The reservoir may be filled such that prior to the step of filling the jack, the jack and the reservoir contact each other or almost contact each other, such that the jack needs to make only a short stroke from the initial condition to the extended condition. After the construction pit has been excavated between the upright walls and the work has been finished, the pressing force onto the strut can be removed by emptying the reservoir, after which the strut, the jack and the reservoir can be removed.

[0026] By filling the jack with the curable medium at elevated pressure, the upright walls can be pressed against soil at the outer sides and the entire structure can be prestressed.

[0027] Hereinafter, the invention will be elucidated further by means of drawings, which show embodiments of the invention very schematically. Fig. 1 is a perspective view of a part of an embodiment of a strut structure according to the invention. Fig. 2 is a top view of the strut structure according to Fig. 1. Fig. 3 is a perspective view of a pressure body of the strut structure according to Fig. 1 on a larger scale. Fig. 4 is a top view of the pressure body of the strut structure as shown in Fig. 3. Fig. 5 is a sectional view along the line V-V in Fig. 4. Fig. 6 is a similar view as Fig. 4, but shows a pressure body of the strut structure according to an alternative embodiment. Fig. 7 is a sectional view along the line VII-VII in Fig. 6. Fig. 8 is an enlarged view along the line VIII-VIII in Fig. 7. Fig. 9 is an enlarged view along the line IX-IX in Fig. 7. Fig. 10 is a perspective view of a jack in the pressure body according to Fig. 6 in an extended condition of the jack. Fig. 11 is a sectional view of a jack strut according to Fig. 10. Fig. 12 is a similar view as Fig. 10, but shows the jack in an initial condition thereof. Fig. 13 is a sectional view of the jack according to Fig. 12.

[0028] Figs. 1 and 2 show a part of an embodiment of a strut structure 1 for a construction pit according to the invention. The strut structure 1 comprises retaining walls 2 in the form of a sheet pile wall profile which separate the construction pit from the environment. Along the inner sides of the retaining walls 2 respective waler beams 3 are provided, which are coupled to each other in order to form a waler frame along the inner circumference of the retaining walls 2.

[0029] The strut structure 1 further comprises elongate struts 4, which in this case are arranged as tubes including square flanges at opposite ends thereof. The waler beams 3 are pressed against the retaining walls 2 by the struts 4 by means of jacks 5, which are provided inside respective pressure bodies 6. The pressure bodies 6 are located in alignment of the respective struts 4. Fig. 1 shows that one assembly of one of the struts 4 and one of the pressure bodies 6 is located between opposite retaining walls 2, whereas two of such assemblies are located between two adjacent and angled retaining walls as diagonal braces. One of the pressure bodies 6 is shown in detail in Figs. 3-5.

[0030] The pressure body 6 comprises an outer tube 7 and an inner tube 8 which fits extendably telescopically in the outer tube 7. The inner tube 8 has a first end, which protrudes outside the outer tube 7 and is provided with an end plate 9. The end plate 9 is mounted to a flange of the corresponding strut 4. This means that in fact the inner tube 8 becomes part of the strut 4. A second end of the inner tube 8 which is located in the inner tube 7 is also provided with an end plate 10.

[0031] In the outer tube 7 the jack 5 and a reservoir 12 are located next to the end plate 10 of the inner tube 8. The reservoir 12 is provided with a closable fill opening 13 and a closable discharge opening 14. The reservoir 12 may be filled with dry sand, but this may possibly be a different incompressible and liquid medium. The jack 5 is provided with two opposite pressure plates 15a, 15b which are coupled to each other along their circumference by a flexible wall 16. For example, the flexible wall 16 may be made of rubber which is vulcanized against the pressure plates 15a, 15b. The flexible wall 16 provides the opportunity to move the pressure plates 15a, 15b with respect to each other in the longitudinal direction of the strut 4.

[0032] The pressure plates 15a, 15b and the flexible wall 16 form an enclosure of an expandable space 17, which can be filled with a curable material at elevated pressure, for example grout, via a connection 18 in one of the pressure plates 15b. The curable material can be supplied from outside through the inner tube 8 via a channel 19. In the embodiment as shown the jack 5 is located between the reservoir 12 and the strut 4 in alignment with the strut 4. Hence, the strut 4, the jack 5 and the reservoir 12 are arranged in series between the retaining walls 2. One of the pressure plates 15b abuts the end plate 10 of the inner tube 8.

[0033] The reservoir 12 is formed by the outer tube 7, an end plate 20 of the outer tube 7, one of the pressure plates 15a of the jack 5 and the flexible wall 16 of the jack 5. At a side of the reservoir 12 which faces the strut 4 the reservoir 12 is bordered by one of the pressure plates 15a of the jack 5 and the flexible wall 16 which abuts the outer tube 7 when the space 17 of the jack 5 is pressurized. The length of the reservoir 12 in the longitudinal direction of the strut 4 is variable by moving the jack 5 inside the outer tube 7 in longitudinal direction of the jack 4, such that at least the one pressure plate 15a of the jack 5 which borders the reservoir 12 is in a different position. The end plate 20 of the outer tube 7 which is located opposite the one pressure plate 15a is mounted to one of the waler beams 3.

[0034] When the pressurized curable material is inserted into the space 17 between the pressure plates 15a, 15b and the flexible wall 16 of the jack 5, the pressure plates 15a, 15b tend to move away from each other and press the flexible wall 16 against an inner side of the outer tube 7. This means that the sand in the reservoir 12, although substantially incompressible, is slightly compressed and the retaining walls 2 at either side of the strut 4 and the pressure body 6 will be pushed away from each other from a first mutual position to a second mutual position. After reaching the second mutual position the supply of the curable material may be stopped and the material cured, such that the jack 5 is secured in the extended position thereof. This means that the jack 5 is lockable in the second mutual position. It is also possible to fill the space 17 such that the retaining walls 2 are not pushed away from each other, but are only locked in the mutual positions. After locking the construction pit can be excavated and the retaining walls 2 will exert a pressing force onto the strut 4, the jack 5 and the reservoir 12.

[0035] In the embodiment as shown the jack 5 is located between the reservoir 12 and the strut 4, but it is also conceivable that the reservoir 12 is located between the jack 5 and the strut 4 or that the reservoir 12 is located outside the pressure body 6.

[0036] Fig. 5 makes clear that the jack 5 forms a relatively simple part of the strut structure 1. The jack 5 has a relatively short stroke. Since the jack 5 may be located at different positions within the inner tube 7 in longitudinal direction of the jack 4 the volume of the reservoir 12 is very flexible. For example, if a similar strut 4 is applied at a strut structure wherein a larger distance must be bridged the jack 5 according to Fig. 5 may be positioned at a larger distance from the end plate 20 of the outer tube 7 and the space in the reservoir 12 can be filled with a larger amount of sand before inserting the pressurized curable material into the space 17.

[0037] When the strut 4 and the pressure body 6 must be decoupled from the retaining walls 2 the discharge opening 14 of the reservoir 12 can be opened, such that dry sand leaves therefrom and the inner tube 8 can be slid further into the outer tube 7 in order to eliminate the pressing force from the retaining walls 2 on the jack 5, the reservoir 12 and the strut 4.

[0038] Figs. 6-13 show parts of an alternative embodiment of the strut structure 1. This embodiment has a lot of similarities to the embodiment as described hereinbefore; similar elements are indicated with the same reference numbers. Figs. 10-13 show the jack 5 as a separate part, in Figs. 12 and 13 in an initial condition and in Figs. 10 and 11 in an extended condition. In this embodiment the jack 5 is made from a flexible material. The pressure plates 15a, 15b are also flexible and abut the end plate 20 of the outer tube 7 and an opposite rigid plate 21, respectively, in the outer tube 7 of the pressure body 6. The plate 21 is displaceable in longitudinal direction of the outer tube 7 with respect to the outer tube 7 and forms a wall of the reservoir 12. An opposite wall of the reservoir 12 is formed by the end plate 10 of the inner tube 8. The flexible wall 16 of the jack 5 has an accordion shape, such that the pressure plates 15a, 15b are parallel to each other in both the initial condition and the extended condition. The jack 5 has two connections 18 which protrude radially outwardly through the outer tube 7 for filling the space 17 with a curable material and deaerating the space 17 during filling, respectively. Fig. 7 shows that the reservoir 12 in this embodiment is located between the jack 5 and the strut 4.

[0039] The invention is not limited to the embodiments as shown in the drawings and described hereinbefore which can be varied in different manners within the scope of the invention.

Claims

1. A strut structure (1) for a construction pit, comprising two upright walls (2), and a jack (5) and an elongated strut (4) arranged in series therebetween, wherein the jack (5) is extendable from an initial condition to an extended condition and lockable in the extended condition, characterized in that the strut structure (1) is further provided with a closable reservoir (12) for receiving a substantially incompressible and liquid medium, which reservoir (12) is arranged between one of the walls (2) and the strut, wherein at least in an empty condition of the reservoir (12) the length of the reservoir (12) is variable in longitudinal direction of the strut (4).

2. A strut structure (1) according to claim 1, wherein the strut (4), the jack (5) and the reservoir (12) are arranged in series, wherein optionally the jack (5) and the reservoir (12) are located in alignment with the strut (4), and / or wherein the jack (5) is located between the reservoir (12) and the strut (4).

3. A strut structure (1) according to claim 1 or 2, wherein the jack (5) comprises a space (17) which is expandable in longitudinal direction of the strut (4), wherein the space (17) includes an enclosure (15a, 15b, 16), which is provided with a connection (18) for supplying a medium at elevated pressure into the space (17).

4. A strut structure (1) according to claim 3, wherein the enclosure is provided with two opposite side walls (15a, 15b) which extend transversely to the longitudinal direction of the strut (4) and are movable relative to each other in longitudinal direction of the strut (4).

5. A strut structure (1) according to claim 4, wherein the side walls (15a, 15b) are rigid or wherein the side walls (15a, 15b) are flexible.

6. A strut structure (1) according to claim 4 or 5, wherein the side walls (15a, 15b) are connected to each other by a flexible wall (16), which together with the side walls (15a, 15b), enclose the space (17).

7. A strut structure (1) according to claim 6, wherein the flexible wall (16) has an accordion shape.

8. A strut structure (1) according to claim 4, wherein the side walls (15a, 15b) are flexible and connected to each other by a flexible wall (16), which together with the side walls (15a, 15b) encloses the space (17), wherein the side walls (15a, 15b) and the flexible wall (16) are made in one piece.

9. A strut structure (1) according to any one of the claims 3-8, wherein the jack (5) can be locked in the extended condition by introducing a curable material into the expandable space (17).

10. A strut structure (1) according to any one of the preceding claims, wherein the reservoir (12) has a housing (7, 10, 20, 21, 15a, 16) including a wall (15a, 21) which is movable in the longitudinal direction of the strut (4), which wall extends transversely to the longitudinal direction of the strut (4).

11. A strut structure (1) according to claim 10 and any one of the claims 4-9, wherein the movable wall is adjacent to or coincides with one of the side walls (15a) of the jack (5).

12. A strut structure (1) according to claims 10 and 11, wherein the housing of the reservoir (12) comprises a tube (7) with the movable wall (15a, 21) therein and in which the jack (5) is also located.

13. A strut structure (1) according to any one of the claims 6-8 and claim 12, wherein the flexible wall (16) of the jack (5) abuts the tube (7) in the extended condition of the jack (5).

14. A method for locking the strut structure according to any one of the preceding claims, comprising the following sequential steps: placing the jack (5) in its initial condition, the strut (4) and the reservoir (12) in series behind each other between the upright walls (2), filling the reservoir (12) with an incompressible and liquid medium, like dry sand, filling the jack (5) with a curable medium, like grout, such that the jack (5) is extended from the initial condition to the extended condition, and curing the curable medium.

15. A method according to claim 14, wherein the jack (5) is filled with the curable medium at elevated pressure.

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