ARRANGING AN ANCHOR PILE IN UNCONSOLIDATED MATERIALS

The present invention relates to an unconsolidated material anchor device which is designed to achieve high anchor capacity in deeper lying unconsolidated materials. The anchor device is preferably designed to be pushed down into the seabed with conventional piling frame equipment.

Nowadays various types of anchors are known within the area of the present invention and examples of some of these are discussed below.

Conventional plate anchors or ship anchors, for example type "Vryhof". These are designed so that vessels with high towing power pull the anchors so that they dig themselves down into the seabed. These types of anchors are widespread, but also have some disadvantages. In some cases, the unconsolidated materials are of such a nature that the anchors cannot be pulled down to a sufficiently large depth to achieve the necessary holding force.

Anchor piles normally designed as steel pipe piles. These are installed using pile hammers. These anchors normally have a small diameter and may give too low holding resistance. Furthermore, they have a constant cross-section which entails a relatively large material consumption in upper soil layers with little holding resistance. Suction anchor. These are installed by mechanical pumps attached to the pile and are sucked into the ground. These anchors have a constant cross-section which results in relatively large material consumption in the upper soil layer with little holding resistance. Furthermore, they require a lid on top to establish suction. They also require a special mechanical system to enable installation into the

unconsolidated materials by means of suction.

SEPLA-anchors. These are designed as a plate anchor and pressed into the unconsolidated materials by means of a suction anchor. This normally results in a complicated operation.

An object of the present invention is therefore to provide an unconsolidated material anchor device which solves the disadvantages and problems of the known anchor types as discussed above.

Another object is that the anchor device should be manufacturable and transportable in a cost-effective manner.

A further object is that the anchor device should be installable in an exact, predetermined position by means of standard frame equipment for piles.

A further object is that the unconsolidated material anchor device should achieve high anchor capacity in deeper lying unconsolidated materials.

The objects of the present invention are achieved by an unconsolidated material anchor device, characterized in that it consists of an elongate continuous open box construction with a triangle-shaped cross-section comprising a first wall surface, second wall surface and third wall surface where the first wall surface in its lower end region which is introduced into unconsolidated materials is extended beyond connecting areas with the two adjacent second and third wall surfaces whereby two cantilevered wall surfaces are formed and that in an lower area of connection area between the second and third wall surface an anchor pile is arranged.

Preferred embodiments of the unconsolidated material anchor device are elaborated in claims 2 to 5.

The objects of the present invention are also achieved by a method for arranging an anchorage in unconsolidated materials, characterized in that it comprises:

providing an unconsolidated material anchor device consisting of an elongate continuous open box construction with a triangle-shaped cross-section comprising a first wall surface, second wall surface and third wall surface where the first wall surface in its lower end region which is introduced into unconsolidated materials is extended beyond connecting areas with the two adjacent second and third wall surfaces whereby two cantilevered wall surfaces are formed and in that in an lower area of the connecting area between the second and third wall surface an anchor pile is arranged, and

that the unconsolidated material anchor device with an attached anchor line is arranged with its lower end area against the unconsolidated materials and pressed into the unconsolidated materials with conventional frame equipment for piling.

Preferred embodiments of the method are further elaborated in claims 7 to 9.

In the following, an embodiment of the unconsolidated material anchor device according to the invention will be explained with reference to the appended figures, in which fig. 1 shows an embodiment of an unconsolidated material anchor device according to the invention.

Referring to figure 1 , there is shown a unconsolidated material anchor device 1 which is arranged in a vertical position. The unconsolidated material anchor device 1 consists of an elongate continuous open box construction with a triangular cross- section comprising a first wall surface 5, second wall surface 10 and third wall surface 15. The first wall surface 5 is in its lower end area which is inserted into unconsolidated materials extended beyond connecting areas 5a, 5b with the two adjacent second and third wall surfaces 10, 15. Two cantilevered wall surfaces 8a, 8b are thus formed. In a lower area of connecting area 5c between the second and third wall surfaces 10, 15 an anchor pile 20 is arranged.

The triangle-shaped cross-section of the elongate box construction in this

embodiment is an equilateral triangle. The triangular cross-section of the elongate box construction can also be a non-equilateral triangle.

Anchor piles 20 are arranged in the lower area of the unconsolidated material anchor device where the total, resulting holding resistance from the adjacent soil masses appears to be selected based on the ground resistance distribution of the height of the anchor device.

The unconsolidated material device 1 will preferably be made of steel, but other materials can also be used.

In the shown embodiment the unconsolidated material anchor device 1 is a triangular through-going open steel box. The first wall surface 5 is protruded from the cassette cross section at the lower part of the box to increase the holding capacity of the anchor device 1 in deeper lying ground layers with higher ground resistance. Anchor pile 20 for an anchor line is shown attached in the lower part of the anchor device 1 on level with the total resulting holding resistance from the adjacent soil masses. In this way, the unconsolidated material anchor device 1 will be able to utilize the horizontal ground resistance.

Depending on the required holding force and the local ground conditions, the anchor device 1 can be designed by varying its geometry such as for example:

i) the length of the elongate continuous open box construction can be varied, ii) the cross-sectional shape of the continuous open box construction can be either an equilateral or a non-equilateral triangle,

iii) length and width of the cantilevered wall surfaces 8a, 8b can be varied, iv) anchor pile 20 can be selected based on the distribution of the ground resistance over the height of the anchor device.

The unconsolidated material anchor device 1 is, as shown in figure 1 , designed from straight plates which offer a simple and cost-effective manufacturing method. The anchor device can be manufactured and transported lying on the first wall surface 5. The unconsolidated material anchor device 1 with an elongated box construction and triangle-shaped cross-section implies that the forces from the anchor line are distributed over the total height of the anchor device 1 to the surrounding

unconsolidated materials by the inherent properties of the open box construction as a continuous beam.

As previously mentioned, the unconsolidated material anchor device 1 is designed with a view to being pressed down into the seabed by means of conventional frame equipment for piling. The frame equipment can, for example, be conventional pile hammers (drop weights or hydraulic hammers) or vibro-hammers. The piling equipment can advantageously be mounted on the anchor device 1 on board of a suitable installation vessel and lowered as a unit down to the seabed. Further driving of the anchor device 1 down into the unconsolidated materials takes place as for framing of free-standing piles.

After use, it will be possible to pull up the anchor device 1 for reuse or use of a vibro- hammer combined with an upward tensile force.

The unconsolidated material anchor device 1 is designed so that its installation does not have any limitations with regards to soil profile. Different soil profiles will therefore not limit the use of the unconsolidated material anchor device 1. The soil profiles often show an increasing strength with depth. The present unconsolidated material anchor device 1 is designed so that it uses as little structural material as possible in upper soil layers but uses more structural material in deeper and firmer soil layers. There is no need to use specially made auxiliary equipment beyond standard pile hammers for installation. The anchor device 1 can be installed in an exact, predetermined position.

Finally, it should be mentioned that the previously known anchor solutions each have one or more of the properties and advantages that the anchor device 1 according to the invention has, but the present unconsolidated material anchor device 1 enables all these properties to be integrated in a new anchor concept.