|Disaster Rescue - Australian Emergency Manual (Natural Disaster Organization, 183 p.)|
|CHAPTER EIGHT - ANCHORS AND HOLDFASTS|
8.3 Picket Holdfasts
In ordinary soil, pickets are suitable as holdfasts for loads up to 2 tonnes. They may be used as single pickets or, when formed into a holdfast, may be arranged as 1 and 1; 2 and 1; 3, 2 and 1 systems, according to need. The following points should be observed:
(a) The pickets should be driven into the ground as close as possible to an angle of 45 degrees away from the line of pull, with two-thirds of their length into the ground. The strongest picket should be nearest the load.
(b) The lashings connecting the pickets should be at 90 degrees to the pickets and should go from the head of the one in front to ground level on the one behind. This determines the distance between the pickets, which should never be less than 1m apart.
(c) Anchor systems should be monitored at all times.
(d) As a rough guide to safe working loads a 1.5m x 25mm mild steel picket properly driven into ground with good holding qualities will safely support a load of 350kg.
As the number of pickets in the holdfast is increased, the load it will support is increased by 350kg for each picket.