Holding capacity table

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Holding capacities* Flimit in kN
(the figures represent the breaking load)

Disc diameter D (mm) Screw-in depth (m)   Soil with a heavy consistency, fatty, stiff clays, extremely desiccated soil filled with pebbles, boulders and stones Well-graded sand-gravel mixture, evenly grained gravel with few fine components (medium-heavy soil) Gravelly sand, coarse-grained, consolidated Cohesive soils, semi-solid, easily to heavily ductility, clay, marl, loess, loam Backfilled soil that has not been artificially compacted, with little cohesion, fine grained sands
80 0,70 4,9 4,2 3,6 2,3 2,0
100 0,70
1,00		 6,0
9,3		 5,1
7,8		 4,1
6,4		 3,1
4,9		 2,4
3,9
120 0,70
1,00		 7,8
12,2		 6,7
10,4		 5,1
8,2		 4,2
6,3		 3,2
4,9
150 0,70
1,00
1,50
2,00		 10,8
16,7
29,4
54,0		 9,3
14,2
27,5
39,2		 6,7
10,8
23,5
31,4		 5,9
8,6
17,7
24,5		 4,4
7,0
11,8
21,6
200 0,70
1,00
1,50
2,00		 15,7
24,5
44,2
71,1		 14,2
21,6
39,2
58,9		 10,8
16,7
35,3
47,0		 8,8
12,7
26,5
37,3		 6,7
10,8
17,7
29,4
250 0,70
1,00
1,50
2,00		 19,6
29,4
53,0
80,4		 17,7
24,5
47,0
68,7		 13,3
19,6
41,2
54,0		 10,8
14,2
31,4
41,1		 8,3
12,7
20,6
30,4
300 1,00
1,50
2,00		 32,8
56,9
88,3		 27,5
51,0
73,6		 21,6
45,1
56,9		 17,7
34,3
44,1		 13,7
22,5
32,4
350 1,00
1,50
2,00		 41,2
73,6
117,7		 35,3
66,8
98,1		 27,4
58,9
78,5		 21,6
44,1
61,8		 17,8
29,4
55,9

* Please note: Order length = screw-in depth plus approx. 30 cm for eyelet and distance to the disc
* = Holding forces were determined in grown soils

Proceed here as follows:

1. Determine the type of soil
Determine the type of soil based on the classifications given in the holding capacity table.

2. Determine the holding capacity
Determine the maximum holding capacity required. As the holding capacity table deals with breaking loads, it is advisable to build in a corresponding safety factor for the relevant use.

3. Determine the screw-in depth
The screw-in depth can generally be freely selected. In the case of permanent anchors, there should always be a layer of soil between 70-100 cm deep above the anchor disc that is not subject to seasonal influences (humidity, desiccation, frost, thawing periods). In normally cultivated soil, this corresponds to a total screw-in depth for the anchor of around 1.20-1.50 m. Selecting a higher value for the screw-in depth for the anchor will not necessarily result in a higher holding capacity. Rather this will only be the case when more solid layers of soil or at least no softer layers of soil are reached. It is actually possible under certain circumstances that the anchor could penetrate into softer layers of soil when it is screwed in deeper which will even reduce the holding capacity.

4. Determine the disc diameter
Once the type of soil, desired holding capacity and screw-in depth have been determined, the disc diameter can be read off the holding capacity table.

Note on the holding capacity table

The holding capacities within a soil group are still subject to lots of other factors. Alongside the distribution of the grain sizes, the bulk density, soil stratification, water content (in some cases also the groundwater level) and the associated capillary forces can impact the holding capacity in different ways. In addition, these factors can also change as the screw-in depth increases. Therefore, the holding capacity table can only provide guidance.

Although the stated loads represent so-called breaking loads, i.e. the structure of the soil can collapse at this load, significantly higher holding capacities than those stated have also been achieved in numerous tests. The materials used for the anchors themselves can withstand significantly higher loads (depending on the shaft strength and the thread size). As the type of soil, soil structure, water content, bulk density and any possible capillary forces can only be determined with a significant amount of effort, we recommend calculating the required size of the anchor by carrying out a tensile test at the intended installation site. This method will ensure that all factors that could have a possible positive or negative influence on the holding capacity are taken into account, without the need for extensive soil tests and subsequent calculations. The actual holding capacities can then be precisely measured.

Structural calculations:

If you require a corresponding calculation to verify the structural strength of the anchor, our certified structural engineers can carry out a structural calculation (subject to a charge) insofar as a soil survey that includes the required information is made available.