EP2955275A1 - Geotextile sand container and method for lowering same - Google Patents

Abstract

Geotextile sand container (1) for underwater protection of buildings, in particular as Kolkschutz with a geotextile sheath (10) and a sand filling (2), wherein in installation position lying below section (11) of the sand container (1) with a water-saturated filling and / or Addition of compared to the remaining sand filling (2) of the sand container (1) heavier material (21) has a higher density. Further, a method for lowering geotextile sand container is disclosed, wherein the sand container (1) positioned on the water surface and is released so that it sinks to the seabed, the sand container (1) with its in-mounting position down, ballastierten section (11) the water surface is set, immersed and released in this orientation.

Description

The invention relates to a geotextile sand container for underwater protection of buildings, in particular as Kolkschutz with a geotextile shell and a sand filling. Furthermore, the invention relates to a method for lowering geotextile sand containers, wherein the sand container is positioned on the water surface and released, so that it sinks to the seabed.

Such geotextile sand containers are known in coastal protection in a variety of arrangement and application and different sizes. Exemplary is a publication at HCU Symposium Geoinformationen for the coastal zone of 07. October 2010 "Geotextile Sand Containers in Coastal Protection" by Matthias Bleck, Uwe Momsen and Michael Schöner The KED engineers Knabe Enders Dührkop Engineers GmbH referenced. From this, the use of geotextile sand containers as Kolkschutz to foundation structures, such as monopiles known.

Basically, any submerged underwater structure interferes with the dynamic balance between the body of water and the mobile seabed. Interactions between the foundation structure, the hydrodynamic stresses and the seabed, which consists, for example, of more or less dense sands, result in erosion and sedimentation processes in the vicinity of the structure as well as loosening up of the seabed in a larger environment. In particular, bottom changes in the vicinity, the so-called pitting, endanger the stability of the foundation structure or structure. It is therefore necessary to provide suitable Kolkschutzmaßnahmen. For this there are investigations and publications, which are concerned in particular with the Kolkschutz for the establishment of offshore wind energy plants, as in the magazine Geotechnik 34 (2011), pages 51 to 58 "Anti-collapse protection for offshore wind turbines in the North Sea", by Georg Heerten and Karsten Peters such as " Kolkschutz on monopile supporting structures from OWEA "by Grüne et al. FZK, Hanover. In particular, it also reports on the use of geotextile sand containers for scour protection in the vicinity of monopile supporting structures.

The US 2009/0 208 288 A1 describes a flexible, water-permeable tube made of a geotextile for receiving a filling material, wherein the tube spans at its two opposite ends after receiving the filler flat plane end faces, so that in the longitudinal direction joined together such sand tubes result in a seamless transition. It is thus avoided that ocean currents can attack at adjacent ends of the sand tubes.

In the publication in the proceedings of the 8th FZK Colloquium " Maritime Hydraulic Engineering and Coastal Engineering ", Hanover, dated 10 March 2011, Dassanayake et al. in "sinking behavior and deformation of geotextile sand containers during installation of scour protection for marine and offshore structures", the sinking behavior and any deformations on geotextile sand containers when freely sinking to the seabed are investigated. In particular, the poor predictability of the trajectory of the sand container was recognized as a problem when descending. In this scientific development it was determined that with pillow-shaped sand containers a lower dispersion of the determined trajectories can be achieved if the pillow-shaped sand container is laid flat with its largest cross-section on the water surface and thus a drop is orthogonal to the largest cross-sectional area of the sand container.

Based on this prior art, it is an object of the invention to form a geotextile sand container so that it largely as possible performs uniform Absinkbewegung by the body of water and reaches the seabed in a predeterminable orientation.

This object is achieved with a geotextile sand container having the features of patent claim 1 and a method according to claim 8.

The fact that a lying in installation position below section of the sand container with a water-saturated filling and / or by adding compared to the remaining sand filling of the sand container heavier material has a higher density, the lower portion of the sand container is ballasted, bringing a more stable position in the Sinking in the water body takes and rotation and lateral movements are prevented or reduced. Consequently, a sand container can be positioned by a ship by free sinking through the body of water much more accurately on the seabed. The trajectory of the sand container through the body of water is determined by the ballast clearly targeted and not by random tumbling movements, rotations and lateral sliding.

According to the sand container is placed with its in installation position down, ballastierten section on the water surface, immersed and released in this orientation, in the sinking the container holds by the ballast its relative orientation in the water body and decreases according to its relative weight in the water and its flow resistance in Essentially straightforward to the seabed.

The flow around the sand container when sinking can be optimized by the fact that the geotextile shell has formed in its in-mounting position below section a tip, convex protrusion or three-sided prism. This flow optimization further stabilizes the sinking behavior and increases the sinking rate.

Alternatively, the known cushion shape of the geotextile sand container can be maintained, the installation position with its largest cross-section flat oriented on the seabed. Experiments have shown that in a pillow-shaped sand container a sinking with its largest cross-section oriented normal to Absinkrichtung represents a stable position in the water, which is a substantially straight-line sinking. However, in the known pillow shape, the sinking process is relatively slow, since the flow resistance around the pillow is relatively high. Accordingly, there is a higher risk of dripping with larger water depths and / or stronger ocean currents.

In addition, hydrodynamic guide vanes are formed on the longitudinal sides of the sand container oriented in the installation position. This guide wings stabilize the sinking of the ballasted sand container, especially at a faster sinking speed, which is made possible by a hydrodynamically optimized shaping of the sand container, for example in the manner of a torpedo armature. Preferably, the guide vanes are formed from the geotextile of the shell, as there are thus no further different materials to be provided on the sand container and damage to adjacent and / or passing sand containers are avoided.

If the sand container is designed to be elongated in the sinking direction, the flow resistance in the water body in the sinking direction decreases significantly, preferably together with the features of subclaim 2, so that the sinking rate increases.

When the sand container tapers towards the upper end in Absinkrichtung, the flow resistance is further reduced, so that the sand container in the manner of a torpedo armature with a relatively high rate of descent and thus in a very straightforward and by other influences, such as the ocean currents, hardly affected kind to Seabed will sink.

According to the method, it is important that the sand container to be lowered is released spontaneously without transmitting motion impulses to the sand container. Thus it can be avoided that the sand container at the moment of letting go in the body of water still receives a change in orientation and thus does not meet its actual destination on the seabed with sufficient accuracy.

If ocean currents in the water body are measured and / or estimated in the target area for accurately positioning the sand container on the water surface, the storage target on the seabed for the sand container can be precisely reached by providing calculated hold even with relatively slowly sinking sand containers (pillow containers) or with very strong ocean currents ,

Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying schematic diagrams.

Fig. 1

einen ballastierten Sandcontainer in einer ersten Ausführungsform,

Fig. 2

eine alternative Ausführungsform zur Figur 1,

Fig. 3

einen zylindrischen Sandcontainer mit kegelförmiger Spitze,

Fig. 4

einen zylinderförmigen Sandcontainer mit Flügeln und

Fig. 5

eine alternative Form für einen Sandcontainer.

It shows:

Fig. 1

a ballasted sand container in a first embodiment,

Fig. 2

an alternative embodiment to FIG. 1 .

Fig. 3

a cylindrical sand container with a conical tip,

Fig. 4

a cylindrical sand container with wings and

Fig. 5

an alternative form for a sand container.

Fig. 1 shows a sand container 1 with a possible elongated shape with a geotextile sheath 10 and a sand filling 2 received therein. A lying in installation position portion 11 of the sand container 1 is ballasted by that therein heavier material 21, for example with water saturated sand or gravel is filled. In the remaining area 12 of the shell 10 of the sand container 1 dry sand 22 is filled. This can be achieved, for example, with a sand container completely filled with dry sand, which is in a proper orientation in a water bath prior to installation, which leads to ballast (water saturation) of the lower, standing in the water part of the sand container.

Alternatively to in FIG. 1 shown vertically elongated shape of the sand container 1 is in FIG. 2 a similarly shaped sand container 1 shown, the lying in the installed position section 11, however, along a long side of the sand container 1 is arranged.

In a further embodiment is in FIG. 3 a cylindrical sand container 1 is shown, which has a downwardly tapered conical shape in its lower position in the mounting position 11 in the shell 10, so that this sand container 1 sinks during the sinking process through the ballast and the flow-technically meaningful cone shape to the cylinder axis of the sand container.

In a further embodiment is in FIG. 4 a sand container 1 shown, which in turn has a cylindrical basic shape, but in addition to the ballasting of a lying in position below section 11 by heavy material 21, for example water saturated sand and / or gravel four wings 15 on its formed in Zylindermantelform longitudinal side. When descending to the seabed in the body of water, the wings 15 stabilize the trajectory of the sand container 1. The wings 15 are the stronger, the higher the relative speed (descent) of the sand container 1 in the water body.

In a further alternative design according to FIG. 5 For example, a sand container 1 has a substantially cylindrical shell 10, but in which the underlying section 11 has a conical tip 13 which is ballasted. Further points this embodiment, the attached on the cylinder jacket-shaped longitudinal side wings 15. In a sinking movement in the direction of the cylinder axis 14, the water is displaced centering in the Absinkbewegung and stabilized by the relative movement in the body of water along the wings 15, the Absinkbewegung.

In a non-illustrated embodiment, the upper end of the sand container tapers, so that a further reduction of the hydraulic resistance is achieved in the sinking of the sand container. Accordingly, the sand container thus formed reaches a relatively high sinking speed, similar to torpedo anchors known.

Overall, it is found that by the ballasting of the sand container in its in-mounting position below section 11 and, if necessary, by hydrodynamically suitable training of the descending motion flowed surface and the opposite surface and formation of wings 15 along the longitudinal sides of the sand container a significant stabilization of the trajectory of the Sand container is reached in the sinking process. Furthermore, an increase in the rate of descent is achieved, so that any lateral flows acting in the body of water have only a small influence on the accuracy of the sand container to be lowered. Furthermore, the sea current can be measured by suitable measuring means and the positioning of the sand container on the water surface can be selected so that the sand container reaches its destination precisely despite the ocean current.

LIST OF REFERENCE NUMBERS

1

sand containers

10

Shell (geotextile)

11

in the installation position below lying section

12

remaining area

13

top

14

Cylinder axis, longitudinal axis

15

wing

2

sand filling

21

heavier material

22

dry sand

Claims (10)

Geotextile sand container (1) for underwater protection of buildings, in particular as Kolkschutz, with a geotextile sheath (10) and a sand filling (2), characterized in that a lower installation position lying portion (11) of the sand container (1) with a water-saturated filling and / or by adding heavier material (21) to heavier material (21) as compared to the remaining sand filling (2) of the sand container (1). Geotextile sand container (1) according to claim 1, characterized in that the geotextile sheath (10) has formed in its mounting position in the bottom portion (11) has a tip (13), convex protrusion or three-sided prism. Geotextile sand container (1) according to claim 1, characterized in that the geotextile sheath (10) has a pillow shape, wherein the mounting position is oriented with its largest cross-section lying flat on the seabed. Geotextile sand container (1) according to claim 1 or 2, characterized in that hydrodynamic guide vanes are formed on the longitudinal sides of the sand container (1) oriented in the installation position. Geotextile sand container (1) according to claim 4, characterized in that the guide vanes are formed from the geotextile of the envelope (10). Geotextile sand container (1) according to claim 1, 2, 4 or 5, characterized in that it is made elongated in Absinkrichtung. Geoxtextiler sand container (1) according to claim 6, characterized in that the sand container (1) tapers to the upper end in Absinkrichtung. Method for lowering geotextile sand containers according to one of claims 1 to 7, wherein the sand container (1) is positioned on the water surface and released so that it sinks to the seabed, characterized in that the sand container (1) with its lying in installation position below, ballasted portion (11) placed on the water surface, immersed and released in this orientation. A method according to claim 8, characterized in that the sand container (1) to be lowered is released spontaneously, without transmitting movement impulses to the sand container (1). A method according to claim 8 or 9, characterized in that ocean currents are measured in the body of water in the target area for accurate positioning of the sand container (1) on the water surface and / or estimated.

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