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PLAY AROUND WITH THE PARAMETERS FOR YOUR OWN MOORING LINE SHAPE |
Anchors are that devices which hold an object in place. In this case, the anchors hold the mooring lines in place and therefore help in the station keeping of any floating vessel or structure. the most commonly used type of anchors for mooring lines is a suction pile anchor and therefore it's design procedure and calculations are illustrated above.
In the design of a suction pile anchor, soil properties play a major role in determining the various parameters such as the Axial bearing capacity and the length of the pile in the sand. Usually every region has it's own unique soil properties and therefore there cannot be a unique design which satisfies them all. For the North sea, usually two layers of soil are present under the sea bed; clay and sand,with clay layer at the top. the typical thickness of the clay layer in the north sea is around 12-16 meters. But again this is a generalisation which may vary along the sea bed.
For the aforementioned calculations, we consider a layer of sand below a layer of clay and all the calculations are consequently based on this assumption. The diagram of the soil structure is shown below.
In the design of a suction pile anchor, soil properties play a major role in determining the various parameters such as the Axial bearing capacity and the length of the pile in the sand. Usually every region has it's own unique soil properties and therefore there cannot be a unique design which satisfies them all. For the North sea, usually two layers of soil are present under the sea bed; clay and sand,with clay layer at the top. the typical thickness of the clay layer in the north sea is around 12-16 meters. But again this is a generalisation which may vary along the sea bed.
For the aforementioned calculations, we consider a layer of sand below a layer of clay and all the calculations are consequently based on this assumption. The diagram of the soil structure is shown below.
For the suction pile anchor in consideration, the design parameters that need to be calculated are the total Bearing capacity of the pile in soil Q, the total length of pile required Ltotal, and for our case, the minimum length of pile required in the sand layer Lsand.
Let us first start with the calculation of the bearing capacity. In geotechnical engineering, bearing capacity is the capacity of soil to support the loads applied to the ground. The bearing capacity of soil is the maximum average contact pressure between the foundation and the soil which should not produce shear failure in the soil. therefore, the total bearing bearing capacity of the suction pile in soil is a summation of three components as shown below;
Let us first start with the calculation of the bearing capacity. In geotechnical engineering, bearing capacity is the capacity of soil to support the loads applied to the ground. The bearing capacity of soil is the maximum average contact pressure between the foundation and the soil which should not produce shear failure in the soil. therefore, the total bearing bearing capacity of the suction pile in soil is a summation of three components as shown below;
Where,
The axial bearing capacity of clay layer:
The axial bearing capacity of clay layer:
The axial bearing capacity of the sand layer:
The end bearing capacity of the unplugged pile:
This total bearing capacity of the suction pile should be greater than or equal to the axial load on the pile in order for the suction pile anchor not to fail. Therefore, by assuming that the total bearing capacity of the suction pile anchor is equal to the axial load; we can determine the minimum length of the pile required in the sand layer.
Sometimes, when the axial load is small for a given clay layer thickness, the required length of the pile in sand is zero. This is because the clay layer is enough to withhold the axial load applied on it and therefore, the presence of the sand layer can be neglected in the design.
To determine what each symbol means can be checked in the table given.
The anchor capacity depends also on the shape of the catenary line from which the tensile force can be determined. Note that this gives a basic calculation of the anchor capacity. To have more engineering approaches of your situation don’t hesitate to contact us.
Sometimes, when the axial load is small for a given clay layer thickness, the required length of the pile in sand is zero. This is because the clay layer is enough to withhold the axial load applied on it and therefore, the presence of the sand layer can be neglected in the design.
To determine what each symbol means can be checked in the table given.
The anchor capacity depends also on the shape of the catenary line from which the tensile force can be determined. Note that this gives a basic calculation of the anchor capacity. To have more engineering approaches of your situation don’t hesitate to contact us.