Snow Anchor Testing

1. Snow Anchor Testing

2. Snow anchor testing was done on February 21st, 2009 at Tombstone Pass, Oregon. • The weather was in the high 30s to low 40s, mostly sunny, and no wind. • The anchors were all placed in an east facing, 15 to 20 degree, slope. • Testing was conducted using a 7/16in static rope, a 4:1 pulley system, and a steady increase in force with no bouncing

3. Testing area and equipment

4. The top 14in of snow could not be work hardened very well in the morning since there was little water content • By the afternoon, the top 14in of snow was wetter and work hardening was fairly effective • Surface work hardening did not extend below about 16in due to the hard layers at 14in and 20in

5. “T” picket was MSR Coyote • “V” picket was Yates Expedition • 8mm sling was Mammut Contact Dyneema • 8mm cord was Liberty Mountain accessory • Dynamometer was a Dillon with a 2,500 pound capacity and a maximum force recording needle • Dynamometer was last verified in 1989 to be within 50 pounds of true force

6. Snow Profile • 0 – 13.8in = fist • 13.8 – 14.6in = 1 finger • 14.6 – 18.5in = 3 finger • 18.5 – 19.7in = pencil • 19.7 – 21.7in = 2 finger • 21.7 – 25.6in = pencil • 25.6 – 27.6in = 4 finger • 27.6 – 28.3in = pencil • 28.3 – 30.3in = 4 finger • 30.3 – 35.4in = 3 finger • 35.4 – 43.3in = 1 finger

7. Anchor 1 • 36in single vertical “T” picket • No hardening • Placed to top of snow pack • Carabiner with 8mm cord • First levers forward at 80 lbs • Total failure at 110 lbs • Failure was levering forward then pulling out

8. Anchor 2 • 20in single vertical “V” picket • No hardening • Placed to top of snow pack • Girth hitch with 8mm sling • First levers forward at 0 lbs • Total failure at 0 lbs • Failure was levering forward then pulling out

9. Anchor 3 • 24in single vertical “T” picket • No hardening • Placed to top of snow pack • Girth hitch with 8mm sling • First levers forward at 0 lbs • Total failure at 0 lbs • Failure was levering forward then pulling out

10. Anchor 4 • 36in single vertical “T” picket • Moderate hardening (45 mins) • Placed to top of snow pack • Carabiner with 8mm cord • First levers forward at 300 lbs • Total failure at 455 lbs • Failure was levering forward then pulling out

11. Anchor 5 • 20in single vertical “V” picket • Moderate hardening (45 mins) • Placed to top of snow pack • Girth hitch with 8mm sling • First levers forward at 225 lbs • Total failure at 270 lbs • Failure was levering forward then pulling out

12. Anchor 6 • 36in double vertical “T” picket • Moderate hardening (45 mins) • Placed to top of snow pack • Girth hitch with 1in webbing and 8mm distributing cord • First levers forward at 450 lbs • Total failure at 640 lbs • Failure was levering forward then pulling out

13. Anchor 7 • 1 fluke • Placed in top soft snow layer • Total force 660 lbs • Never really “failed” but did travel 12ft under the snow on top of a harder layer at 33in

14. Anchor 8 • 1 fluke • Placed in lower harder snow layer • Total failure at 325 lbs • Traveled about 10ft before breaking through the side of a snow bank

15. Anchor 9 • 24in single horizontal “T” picket in front of slot • Moderate to good hardening • Placed 41in down with 26in snow face in front • Girth hitch with 8mm sling • No failure with force of 1,700 lbs (estimate) • Held 3 people on 4:1 system pulling hard downhill

16. Anchor 10 • 36in single horizontal “T” picket in front of slot • Moderate to good hardening • Placed 39in down with 22in snow face in front • Carabiner with 8mm cord • Total failure at 1,375 lbs • Picket broke in half; back web sheared

17. Anchor 11 • 20in single horizontal “V” picket in front of slot • Moderate to good hardening • Placed 33in down with 14in snow face in front • Girth hitch with 8mm sling • Total failure at 755 lbs

18. Anchor 12 • 36in single horizontal “T” picket in back of slot • Good hardening; layers in front and on top of picket • Placed 35in down with 14in snow face in front • Girth hitch with 8mm cord • Total failure at 850 lbs • Picket broke in half; back web sheared

19. Anchor 13 • 24in single horizontal “T” picket in back of slot • Good hardening; layers in front and on top of picket • Placed 35in down with 14in snow face in front • Girth hitch with 8mm sling • Total failure at 1,500 lbs • Picket slid forward about 1 ft before failure

20. Anchor 14 • 36in single horizontal “T” picket in back of slot • Good hardening; layers in front and on top of picket • Placed 35in down with 14in snow face in front • Yolk setup with carabiners 6in in from both ends and equalized with 8mm cord • Moved forward about 6in at 1,825 lbs; no total failure

21. Anchor 15 • 20in single horizontal “V” picket in back of slot • Good hardening; layers in front and on top of picket • Placed 35in down with 14in snow face in front • Girth hitch with 8mm sling • Picket slid forward about 4 ft under the snow at 850 lbs; no total failure

22. Anchor 16 • 20in single horizontal “V” picket in back of slot • Good hardening; layers in front and on top of picket • Placed 35in down with 14in snow face in front • Girth hitch with 8mm sling • Total failure at 1,500 lbs • Picket broke at girth hitch point; sling was frayed for about 1” on one edge

23. Anchor 17 • Work hardened bollard; 4ft by 10ft by 1ft deep • Used 1in webbing around entire bollard • Webbing moved 3ft at 1,150 lbs; no total failure

24. Potential Lessons • Given the snow conditions, some anchors can travel a long distance through the snow and not actually totally fail. • The 36in “T” pickets seem prone to structural failure. It looks like the picket may roll up or down enough to transfer force to the thinner back web which breaks. • The 20in “V” pickets do not seem to perform as well as the 24in “T” pickets. The travel under snow and the structural failure were surprising.

25. Potential Lessons • Given the snow conditions, even three sets of work hardened, backed up, vertical pickets would not have met CMRU’s safety margin. • Given the snow conditions, the most reliable anchor system would be two 24in horizontal “T” pickets with a distributed power point. This would met CMRU’s safety margin. • CMRU needs to explore the use of mid-point clip vertical picket. This has been shown to often be the strongest type of snow anchor.