Test Update
At a recent anchor installers installation seminars, the discussion got around to anchors and metal fatigue. So out of interest, we decided to examine specific diameters of the twelve anchors that had been loaded to the ultimate failure load and pulled from the rock.
It is quite apparent that certain parts of the Eco anchor undergo local extrusion at specific points. The degree of reduction of the diameter, is consistent with the amount of loading and the direction of loading. I should add at this point that all these anchors we loaded in an axial pull.
The diagrams and tables below should give you an insight into the stresses that result in reduction of specific diameters during loading.
Each Eco anchor from the test bed dated 17 August 1995 has had specific diameters measured. The areas from where the measurements were taken are indicated below on the diagram of the Eco anchor.
The reduction in the measurements at the point diameter D, we believe is caused by the manufacturing process and although a reduction means a reduced maximum load, significant work-hardening will make up for any loss. But it may become more brittle in this area.
Anchor |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
New |
Ave |
|
Egress (KN) |
36 |
46.8 |
25.2 |
36 |
45 |
36 |
23.4 |
45 |
54 |
34.2 |
18 |
34.4 |
36.17 |
||
Max Load (KN) |
46.8 |
54 |
29 |
54 |
52.2 |
48.6 |
36.8 |
50.4 |
54 |
44 |
40 |
37.8 |
45.63 |
||
Diameter A |
7.62 |
7.67 |
7.75 |
7.62 |
7.67 |
7.64 |
7.75 |
7.72 |
7.69 |
7.77 |
7.71 |
7.77 |
7.92 |
7.72 |
|
Diameter Reduction
(mm) |
0.3 |
0.25 |
0.17 |
0.3 |
0.25 |
0.28 |
0.17 |
0.2 |
0.23 |
0.15 |
0.21 |
0.15 |
0 |
0.2 |
|
Diameter Reduction
(%) |
3.788 |
3.157 |
2.146 |
3.788 |
3.157 |
3.535 |
2.146 |
2.525 |
2.904 |
1.894 |
2.652 |
1.894 |
0 |
2.584 |
|
Diameter B |
7.92 |
7.9 |
7.95 |
7.92 |
7.92 |
7.92 |
7.95 |
7.95 |
7.84 |
7.92 |
7.92 |
7.92 |
7.92 |
7.94 |
|
Diameter Reduction
(mm) |
0 |
0.02 |
-0 |
0 |
0 |
0 |
-0 |
-0 |
0.08 |
0 |
0 |
0 |
0 |
0 |
|
Diameter Reduction
(%) |
0 |
0.253 |
-0.38 |
0 |
0 |
0 |
-0.38 |
-0.38 |
1.01 |
0 |
0 |
0 |
0 |
0.01 |
|
Diameter C |
7.9 |
7.91 |
7.92 |
7.9 |
7.9 |
7.92 |
7.92 |
7.92 |
7.9 |
7.9 |
7.91 |
7.89 |
7.92 |
7.908 |
|
Diameter Reduction
(mm) |
0.02 |
0.01 |
0 |
0.02 |
0.02 |
0 |
0 |
0 |
0.02 |
0.02 |
0.01 |
0.03 |
0 |
0.0115 |
|
Diameter Reduction
(%) |
0.25 |
0.13 |
0 |
0.25 |
0.25 |
0 |
0 |
0 |
0.25 |
0.25 |
0.13 |
0.38 |
0 |
0.15 |
|
Diameter D |
7.67 |
7.67 |
7.77 |
7.8 |
7.82 |
7.72 |
7.77 |
7.66 |
7.57 |
7.87 |
7.71 |
7.84 |
7.9 |
7.75 |
|
Diameter Reduction
(mm) |
0.25 |
0.25 |
0.15 |
0.12 |
0.1 |
0.2 |
0.15 |
0.26 |
0.35 |
0.05 |
0.21 |
0.08 |
0.02 |
0.17 |
|
Diameter Reduction
(%) |
3.16 |
3.16 |
1.89 |
1.52 |
1.26 |
2.53 |
1.89 |
3.28 |
4.42 |
0.63 |
2.65 |
1.01 |
0.25 |
2.13 |
|
Diameter E |
7.92 |
7.92 |
7.92 |
7.92 |
7.92 |
7.92 |
7.92 |
7.92 |
7.92 |
7.92 |
7.95 |
7.92 |
7.92 |
7.922 |
|
Diameter Reduction
(mm) |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
-0.03 |
0 |
0 |
-0 |
|
Diameter Reduction
(%) |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
-0.38 |
0 |
0 |
-0.03 |
|
Diameter F |
7.92 |
7.92 |
7.92 |
7.92 |
7.92 |
7.92 |
7.92 |
7.92 |
7.92 |
7.92 |
7.92 |
7.92 |
7.92 |
7.92 |
|
Diameter Reduction
(mm) |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
Diameter Reduction
(%) |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
