WO2015130165A9

WO2015130165A9 - Piping screen

Info

Publication number: WO2015130165A9
Application number: PCT/NL2015/050082
Authority: WO
Inventors: Johannes Kasper Van Eijk; Dries Cornelis Maria STORK; Jeroen Willem DIJKSTRA
Original assignee: Baggermaatschappij Boskalis B.V.
Priority date: 2014-02-25
Filing date: 2015-02-09
Publication date: 2016-03-10
Also published as: EP3111014A1; NL2012325C2; WO2015130165A1

Abstract

The invention relates to an assembly of a screen panel and a screen driving device for driving the screen panel into the ground, wherein the screen panel comprises parallel coupling edges and a geotextile extending between the coupling edges, wherein multiple screen panels are coupled in series at the coupling edges to form a piping screen, wherein the screen driving device comprises a front plate and a back plate that extend parallel and opposite to each other to form an intermediate space between the facing main surfaces of these plates, and a supply of pressurized water or air to insert water or air into the intermediate space, wherein the screen panel is inserted between the front plate and the back plate with the geotextile in the intermediate space.

Description

PIPING SCREEN

BACKGROUND

The invention relates to provisions to control the phenomenon of piping.

The phenomenon of piping occurs for example in dyke constructions having a bottom sand layer that is water permeable and a top clay layer with a dyke that is water impermeable. Seepage water passes through the sand layer at a level just below the clay layer, whereby initial small channels are formed by transport of the sand particles along with the ground water stream. These channels may grow over many years to such extend that the dyke locally shifts sideways, or locally lowers into the sand layer due to collapse of the channels.

Some provisions have already been developed to control the phenomenon of piping, such as installing a geotextile in the ground at the land side of the dyke. The geotextile allows passage of the seepage water and blocks the sand particles contained therein. The geotextile is installed by digging a long, wide and deep trench along the dyke, inserting of the geotextile and filling up the trench again. This method disturbs the initial ground structure to such extend that the dyke may already be weakened. The displacement of the ground while keeping the clay and sand separated requires complex logistics during digging. When the clay is dumped back into the trench at the level of the sand layer it immediately clogs the geotextile, whereby it loses the intended filtering capabilities. It is an object of the present invention to provide provisions to effectively control the phenomenon of piping .

SUMMARY OF THE INVENTION

According to a first aspect, the invention provides an assembly of a screen panel and a screen driving device for driving the screen panel into the ground, wherein the screen panel comprises parallel coupling edges and a geotextile extending between the coupling edges, wherein multiple screen panels are coupled in series at the coupling edges to form a piping screen, wherein the screen driving device comprises a front plate and a back plate that extend parallel and opposite to each other to form an intermediate space between the facing main surfaces of these plates, and a supply of pressurized water, fluid mixture, air or any mixture thereof to insert this into the intermediate space, wherein the screen panel is inserted between the front plate and the back plate with the geotextile in the intermediate space .

In the assembly according to the invention the screen panel to be vertically installed in the ground is inserted between the front plate and the back plate with the geotextile enclosed in the intermediate space. When the screen driving device is driven into the ground, the ground particles are kept outside the intermediate space by continuous insertion of pressurized water, fluid mixture, air or any mixture thereof. In this manner the geotextile can pass a cover layer, such as a clay layer, in order to be partially inserted in a lower sand layer without being clogged prematurely. The screen driving device can be driven into the ground whereby digging of a wide trench is not necessary.

In an embodiment the screen driving device comprises a frame having multiple box girders that are connected to the front plate or the back plate, wherein the box girders are provided with an inlet for the pressurized water, fluid mixture, air or any mixture thereof, and an outlet that debouches into the intermediate space. The box girders then have both the function of stiffening the front plate and the back plate and distribution of the supplied water, fluid mixture, air or any mixture thereof over the intermediate space.

In an embodiment the screen panel comprises a water permeable framework or gauze that is connected to the coupling edges, wherein a geotextile is applied to one or both sides of the framework or gauze. The framework or gauze provides strength to the screen panel and ensures that the geotextile stretches out evenly and smoothly between the coupling edges and does not deform when a pipe occurs next to the geotextile.

In an embodiment the screen panel comprises a flat bottom sheet that is connected to the coupling edges at the bottom sides thereof. The flat bottom sheet provides additional strength to the screen panel so that pushing forces can be transferred from the screen driving device onto the screen panel via the bottom sheet.

In an embodiment thereof the water permeable framework or gauze extends over the flat bottom sheet, preferably with its extremity projecting freely from the flat bottom sheet. The framework or gauze, and the flat bottom sheet can together be folded backwards towards one of the front plate or back plate to push the screen panel into the ground.

In an embodiment the screen driving device comprises a retainer that is movable with respect to the front plate between a retracted position, in which the retainer extends aside the front plate, and an extended position, in which the retainer extends at a distance of the front plate in the direction of the main plane of the front plate. The geotextile and the water permeable framework or gauze, and the flat bottom sheet when present, can project from the distal end of the screen driving device to be folded backwards over the retainer. When the retainer is moved to its extended position after the screen driving device is driven into the ground, the screen panel is slid outside the front plate and back plate while the front plate and the back plate are retracted. The released geotextile is thereby exposed to the ground and anchored.

In an embodiment the retainer is wedge shaped having a pushing tip at front that merges into a wedge face aside, wherein the side face faces away from the front plate .

In an embodiment the water permeable framework or gauze is folded backwards over the frontal pushing edge and against the side face.

In an embodiment thereof the screen driving device is provided with pins projecting from the front plate that penetrate the water permeable framework or gauze. The pins keep the gauze with the geotextile in place during driving the screen driving device into the ground.

In an embodiment the pins are provided with nozzles that are connected to the supply of pressurized water, fluid mixture, air or any mixture thereof. The nozzles can be activated to bring the screen driving device into the ground, or to provide the initial anchoring of the screen panel.

In an embodiment the retainer extends over the entire width of the front plate, whereby the geotextile is evenly retained.

In an embodiment the front plate and the back plate have a width in their main plane that is at least 10 times the width of the intermediate space perpendicular to said main plane.

According to a second aspect, the invention provides a screen panel for forming a piping screen, wherein the screen panel comprises parallel coupling edges and a geotextile extending between the coupling edges, wherein multiple screen panels are coupled in series at the coupling edges to form the piping screen, wherein the screen panel comprises a water permeable framework or gauze that is connected to the coupling edges, wherein the geotextile is applied to one or both sides of the framework or gauze. The coupling edges ensure that the subsequent geotextiles are connected to each other over the entire height, whereby passage of sand particles is effectively blocked. The framework or gauze ensures that the geotextile is kept straight over the years and prevents deformation when a pipe occurs next to the screen panel.

In an embodiment the screen panel comprises a flat bottom sheet that is connected to the coupling edges at the bottom sides thereof. The flat bottom sheet provides additional strength to the screen panel so that pushing forces can be transferred from a screen driving device onto the screen panel via the bottom sheet.

In an embodiment the water permeable framework or gauze extends over the flat bottom sheet, preferably with its extremity projecting freely from the flat bottom sheet in the direction of the main plane of the plat bottom sheet. The water permeable framework or gauze, and the flat bottom sheet can together be folded backwards towards a screen driving device to push the screen panel into the ground.

According to a third aspect, the invention provides a method for forming a piping screen in the ground by means of a screen driving device, wherein the piping screen comprises multiple screen panels having parallel coupling edges and a geotextile extending between the coupling edges, wherein the screen panels are coupled in series at the coupling edges, wherein the screen driving device comprises a front plate and a back plate that extend parallel and opposite to each other to form an intermediate space between the facing main surfaces of these plates, and a supply of pressurized water, fluid mixture, air or any mixture thereof into the intermediate space, wherein the method comprises the steps of insertion of a screen panel between the front plate and the back plate with the geotextile in the intermediate space, insertion of pressurized water, fluid mixture, air or any mixture thereof into the intermediate space while driving the screen driving device into the ground, and retraction of the screen driving device out of the ground, wherein the screen panel remains into the ground and the geotextile is released from the intermediate space to be exposed to the ground.

When the screen driving device is driven into the ground, the ground particles are kept outside the intermediate space by continuous and superfluous insertion of the pressurized water, fluid mixture, air or any mixture thereof. In this manner the geotextile can pass a cover layer, such as a clay layer, to be inserted in a lower sand layer without being clogged prematurely by particles of the cover layer.

In an embodiment thereof the ground comprises a water permeable sand layer and a low water permeable cover layer above the sand layer, wherein the screen driving device is driven into the ground with its distal end into the sand layer, wherein the screen panel remains into the ground with the bottom side of the geotextile into the sand layer and the top side of the geotextile in the cover layer. In this manner the geotextile stretches out over the interface between the sand layer and the clay layer, where the piping phenomenon initiates.

In an embodiment the geotextile remains below the surface of the ground, whereby the surface remains available for other civil purposes.

The various aspects and features described and shown in the specification can be applied, individually, wherever possible. These individual aspects, in particular the aspects and features described in the attached dependent claims, can be made subject of divisional patent applications .

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be elucidated on the basis of an exemplary embodiment shown in the attached drawings, in which :

Figure 1 a civil infrastructure comprising an artificial dyke construction and a screen installation machine for insertion of piping screen panels along the dyke ;

Figure 2 a detail of the screen driving device of figure 1;

Figure 3 the piping screen panels in more detail; and

Figures 4A-4E the subsequent steps during insertion of one of the screen panels into the ground.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 shows an artificial dyke construction 1, which is an exemplary example of a civil construction with a ground configuration in which the piping phenomenon typically might occur. The dyke construction 1 comprises a water permeable lower sand layer 10 and there above a low water permeable or lower water permeable cover layer 20, in this example a clay layer with an elongate dyke 30 that extends along a water body 33 such as an inland canal or river. The dyke 30 has a top face 31 that extends above the water line, a sloping water side 32 that merges into the bottom 35 of the water body, and a sloping land side 34 that in this example merges into a dry land 36. The dry land may extend below the level the bottom 35 of the water body. In this exemplary example the dry land 36 is provided with a drainage canal or trench 37 that extends parallel to the dyke 30. The drainage canal 37 collects water to manage the level of the adjacent ground water. In alternative civil constructions the low water permeable layer cover layer may be formed by peat or silt for example.

In Figure 1 the direction of seepage water from the water body 33 into the dry land is schematically indicated with Arrow A. The seepage water horizontally passes through the water permeable sand layer 10 at a level just below the interface with water impermeable clay layer 20. When the water pressure inside the sand layer 10 becomes higher than the overburden pressure from the clay layer 20, the seepage water can vertically break through to the surface as indicated with arrow B, creating a connection between the sand layer 10 and the surface. This occurs at a location with the lowest pressure, being most of the time below the drainage channel 37 behind the dyke 30. When the pressure difference between the sand layer 10 and the surface water is large, the flow speeds are such that sand particles are transported with the flow of water. This phenomenon is generally known as piping. The pipes thus formed can grow over many years to such extend that the dyke 30 locally shifts sideways, or locally lowers into the sand layer 10 due to collapse of the grown channels. This is prevented with a piping screen 50 according to the invention, which is installed with a screen installation machine 100 according to the invention. The piping screen 50 and the screen installation machine 100 are described in more detail hereafter.

As shown in figure 1, the piping screen 50 comprises a series of interlocked piping screen panels 51 which are shown in more detail in figures 3 and 4B. Each piping screen panel 51 comprises a male slide coupling profile 53 and a shorter female slide coupling profile 54 that extend parallel to each other. The slide coupling profiles 53, 54 are at the bottom side interconnected by a flat bottom sheet or liner 55. The piping screen panel 51 is furthermore provided with a flat gauze sheet 52 that extends between the slide coupling profiles 53, 54 along the length of the female slide coupling 54. The gauze sheet 52 extends downwards at least partly over the flat bottom sheet 55, and may even project freely therefrom. The slide coupling profiles 53, 54 and the flat bottom sheet 55 are made of a flexible plastic, such as polyethylene (PE) . The flat gauze sheet 52 is made of plastic, such as polyethylene, or metal, such as steel, or a felt like material. The piping screen panel 51 is furthermore provided with two sheets of geotextile 56 that are applied to both sides of the gauze sheet 52 to cover the gauze sheet 52 at least between the slide coupling profiles 53, 54. In this example the geotextiles 56 are applied to both sides. Alternatively only one geotextile 56 is applied to cover one side only. The sheets of geotextile 56 are made of plastic, they are water permeable but it blocks sand particles. The geotextile used is adjusted to the local grain size distribution of the sand layer 10. The mesh size is between 60 micrometer and 300 micrometer .

As shown in figure 1, the screen installation machine 100 comprises a crawler crane body 101 having a hoisting mast 102 and a hoisting cable 103. The hoisting cable 103 is connected with a screen driving device 110 pending vertically downwards therefrom. The screen driving device 110 is shown in more detail in figures 2 and 4B.

The screen driving device 110 comprises a flat front plate 111 and an flat back plate 112 made of metal and having the same elongate outer contour. The front plate 111 and the back plate 112 are kept parallel and spaced apart above each other at a constant distance by a rigid metal frame 113 having multiple parallel box girders 114 that extend from a central bridge part 115. Multiple hollow pins 127 with nozzles 128 at the pointed end project downwards from the bottom edge 126 of the front plate 111. At the bottom side the screen driving device 110 is provided with a metal retainer 120 that is wedge shaped. At the back side the retainer 120 is connected with a metal push rod 121 that is slidably guided between two of the box girders 114. The push rod 121 is connected to a hydraulic cylinder 122 that is mounted to the front plate 111. The hydraulic cylinder 122 and the push rod 121 are dimensioned to fall within the vertical projection of the retainer 120 and are protected by the adjacent box girders 114. At the back side the retainer 120 is furthermore connected with two parallel rods 123 that are slidably guided between the box girders 114. In the retracted position of the hydraulic cylinder 122 as shown in figure 3 the tip 125 of the retainer extends along the bottom edge 126 of the flat front plate 111. In the extended position of the hydraulic cylinder 122 as shown in figure 4D the entire retainer 120 extends far below said bottom edge 126.

The screen driving device 110 furthermore comprises inlet pipes 130 that debouches into the hollow box girders 114. The front plate 111 and the box girders 114 are provided with holes that debouches into the intermediate space between the flat front plate 111 and the flat back plate 112, and the nozzles 128 are also connected to the hollow box girders 114. The inlet pipes 130 are connected to a supply of water, a fluid mixture, air or any mixture thereof to inject this between the flat front plate 111 and the flat back plate 112 at a pressure that is much higher than the local ground water pressure at the level of the sand layer 10. The screen driving device 110 is furthermore provided with vibrators to drive the device 110 into the ground.

The installation of the piping screen 50 by means of the screen installation machine 100 is described hereafter under reference to figures 4A-4E.

The screen installation machine 100 is in this exemplary example positioned at the site where the piping screen 50 needs to be installed in the ground. In this example the piping screen 50 is installed vertically and parallel to the dyke 30. At an earlier stage a vertical slot 40 may be formed by insertion of a dedicated tool such as a vibrating plate hanging on the same hoisting cable 103. The screen driving device 110 is hoisted to pend vertically downwards above the ground. A piping screen panel 51 is supplied and laid down on the ground in the proximity of the screen driving device 110. The hydraulic cylinder 122 is retracted.

Subsequently, the longer male slide coupling profile 53 is firstly inserted in direction C between the elongate side edges 116, 117 of the front plate 111 and the flat back plate 112, followed by the female slide coupling profile 54 at the opposite side edge 116, 117. The gauze sheet 52 and the sheet or sheets of geotextile 56 thereby come narrow enclosed between the front plate 111 and the back plate 112. As shown in figure 4B, the piping screen panel 51 is inserted over such length that the flat bottom sheet 55 projects only partly downwards from the bottom edge 126 of the front plate 111. Subsequently, the projecting flat bottom sheet 52 and the flat gauze sheet 52 are folded backwards and upwards in direction D against the retainer 120 to be locally penetrated by the sharp pins 127. The coupling edges of the male slide coupling profile 53 and the female slide coupling profile 54 project freely sideways from the elongate side edges 117, 118 of the flat front plate 111 and the flat back plate 112 while the facing back sides close off the gap between these side edges 117, 118. Finally in this example the supply of water via the inlet pipes 130 is activated, whereby the intermediate space between the front plate 111 and the back plate 112 is fully filled with water and the nozzles 128 of the pins 127 jet downwards. The superfluously injected water continuously escapes along the entire length of the elongate side edges 117, 118 and the bottom edges 126 to prevent that clay or sand enters the intermediate space. The screen driving device 110 is now ready to be vertically inserted into the ground, preferably in the vertical slot 40 that was prepared earlier .

As shown in figure 4C, the screen driving device 110 is driven into the ground in vertical direction E by gravity and with the help of the activated vibrators and the jetting nozzles 128. The screen driving device 110 is inserted to a depth wherein the bottom edge 126 has passed the entire clay layer 20 and is inserted some meters into the sand layer 10. As per design the upper edges of the gauze sheet 52 and the sheet of geotextile 56 are at this depth still located in the clay layer 20, and the upper end of the male slide coupling profile 53 remains above the ground.

As shown in figure 4D, the hydraulic cylinder 122 is subsequently extended, whereby the entire screen driving device 110 except for the retainer 120 is pushed upwards again in direction F. The gauze sheet 52 and the sheet of geotextile 56 are thereby released from the space between the front plate 111 and back plate 112 and are initially exposed to the clay and sand that are locally present at that depth. This anchors the lower side of the piping screen panel 51 whereby the screen driving device 110 can be hoisted further out of the ground in direction F as shown in figure 5E, leaving the piping screen panel 51 behind with only the male slide coupling profile 53 extending above the ground. Finally the hydraulic cylinder 122 is retracted to withdraw the retainer 120 in direction G so as to prepare the screen driving device 110 for installation of the subsequent piping screen panel 51.

The subsequent piping screen panel 51 is inserted into the screen driving device 110 in the same manner as described here before. Before the screen driving device 110 is inserted into the ground, the female slide coupling profile 54 is slid over the part of the male slide coupling profile 53 that extends above the ground. The slide coupling profiles 53, 54 remains interlocked when the screen driving device 110 is driven into the ground. In this manner the piping screen panels 51 are continuously interlocked at the level wherein the sand layer 10 merges into the clay layer 20.

The piping screen 50 thus installed allows passage of seepage water in direction A through the sand layer 10 as shown in figure 1, which is at a level just below the water impermeable clay layer 20. Transport of sand in that direction is effectively blocked by the geotextiles 56. In this manner the structural integrity of the sand layer 10 is ensured. During installation the geotextiles 56 are initially exposed to the ground water when the piping screen panels 51 are released from the water filled screen driving device 110, whereby the clay layer 20 is not able to prematurely clog the geotextiles 56. The interlocked slide coupling profiles 53, 54 and the gauze sheets 52 form a framework that keeps the geotextiles 56 in place during many years. The gauze sheets 52 and the geotextiles 56 provide a stable sandwich construction.

It is to be understood that the above description is included to illustrate the operation of the preferred embodiments and is not meant to limit the scope of the invention. From the above discussion, many variations will be apparent to one skilled in the art that would yet be encompassed by the spirit and scope of the present invention .

Claims

C L A I M S

1. Assembly of a screen panel and a screen driving device for driving the screen panel into the ground, wherein the screen panel comprises parallel coupling edges and a geotextile extending between the coupling edges, wherein multiple screen panels are coupled in series at the coupling edges to form a piping screen, wherein the screen driving device comprises a front plate and a back plate that extend parallel and opposite to each other to form an intermediate space between the facing main surfaces of these plates, and a supply of pressurized water, fluid mixture, air or any mixture thereof to insert this into the intermediate space, wherein the screen panel is inserted between the front plate and the back plate with the geotextile in the intermediate space.

2. Assembly according to claim 1, wherein the screen driving device comprises a frame having multiple box girders that are connected to the front plate or the back plate, wherein the box girders are provided with an inlet for the pressurized water, fluid mixture, air or any mixture thereof, and an outlet that debouches into the intermediate space .

3. Assembly according to claim 1 or 2, wherein the screen panel comprises a water permeable framework or gauze that is connected to the coupling edges, wherein a geotextile is applied to one or both sides of the framework or gauze.

4. Assembly according to any one of the preceding claims, wherein the screen panel comprises a flat bottom sheet that is connected to the coupling edges at the bottom sides thereof.

5. Assembly according to claims 3 and 4, wherein the water permeable framework or gauze extends over the flat bottom sheet, preferably with its extremity projecting freely from the flat bottom sheet.

6. Assembly according to any one of the preceding claims, wherein the screen driving device comprises a retainer that is movable with respect to the front plate between a retracted position, in which the retainer extends aside the front plate, and an extended position, in which the retainer extends at a distance of the front plate in the direction of the main plane of the front plate.

7. Assembly according to claim 6, wherein the retainer is wedge shaped having a pushing tip at front that merges into a wedge face aside, wherein the side face faces away from the front plate.

8. Assembly according to claims 3 and 7, wherein the water permeable framework or gauze is folded backwards over the frontal pushing edge and against the side face.

9. Assembly according to claim 8, wherein the screen driving device is provided with pins projecting from the front plate that penetrate the water permeable framework or gauze.

10. Assembly according to claim 9, wherein the pins are provided with nozzles that are connected to the supply of pressurized water, fluid mixture, air or any mixture thereof.

11. Assembly according to any one of the claims 6- 10, wherein the retainer extends over the entire width of the front plate.

12. Assembly according to any one of the preceding claims, wherein the front plate and the back plate have a width in their main plane that is at least 10 times the width of the intermediate space perpendicular to said main plane .

13. Screen panel for forming a piping screen, wherein the screen panel comprises parallel coupling edges and a geotextile extending between the coupling edges, wherein multiple screen panels are coupled in series at the coupling edges to form the piping screen, wherein the screen panel comprises a water permeable framework or gauze that is connected to the coupling edges, wherein the geotextile is applied to one or both sides of the framework or gauze.

14. Assembly according to claim 13, wherein the screen panel comprises a flat bottom sheet that is connected to the coupling edges at the bottom sides thereof.

15. Assembly according to claims 13 and 14, wherein the water permeable framework or gauze extends over the flat bottom sheet, preferably with its extremity projecting freely from the flat bottom sheet in the direction of the main plane of the plat bottom sheet.

16. Method for forming a piping screen in the ground by means of a screen driving device, wherein the piping screen comprises multiple screen panels having parallel coupling edges and a geotextile extending between the coupling edges, wherein the screen panels are coupled in series at the coupling edges, wherein the screen driving device comprises a front plate and a back plate that extend parallel and opposite to each other to form an intermediate space between the facing main surfaces of these plates, and a supply of pressurized water, fluid mixture, air or any mixture thereof into the intermediate space, wherein the method comprises the steps of insertion of a screen panel between the front plate and the back plate with the geotextile in the intermediate space, insertion of pressurized water, fluid mixture, air or any mixture thereof into the intermediate space while driving the screen driving device into the ground, and retraction of the screen driving device out of the ground, wherein the screen panel remains into the ground and the geotextile is released from the intermediate space to be exposed to the ground.

17. Method according to claim 16, wherein the ground comprises a water permeable sand layer and a low water permeable cover layer above the sand layer, wherein the screen driving device is driven into the ground with its distal end into the sand layer, wherein the screen panel remains into the ground with the bottom side of the geotextile into the sand layer and the top side of the geotextile in the cover layer.

18. Method according to claims 16 and 17, wherein the geotextile remains below the surface of the ground.

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FG/HZ