|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.
8.4 Picket Lashings (Figure 8:2)
The lashing should be started by a Clove Hitch with 12mm rope about 180mm from the head of the front picket. Four turns should be taken around the base of the back picket and the head of the front picket, placing these above the Clove Hitch. Frapping turns should be applied around the lashing, finishing off with a Clove Hitch around the lashing, thus using up whatever spare rope is left. The lashing must be tightened before commencing the frapping turns.
8.5 Buried Holdfasts (Figure 8:3)
With this holdfast, a stout piece of timber, a length of steel girder, a large diameter water pipe or a vehicle spare wheel is required. A trench is dug to accommodate the material used and a small outlet made at right angles to the trench to allow the rope or wire to come to the surface. The greater the load to be applied the deeper the trench should be. It must be appreciated that the buried holdfast is only satisfactory where the angle between ground level and the rope is small. This being the case, the trench need not be filled in, but a rescuer should be detailed to check the holdfast when the initial load is applied.
8.6 Log and Picket Holdfast (Figure 8:4)
As in Figure 8:4, drive in four pickets about 400-500mm apart. Drive in a second row of four pickets 1m behind the first row. Lay a log of sufficient size for the job at hand, behind the first row of pickets. Lash each pair of pickets together.
This method is of particular use in wet or soft earth since the log acts as a beam and bears evenly against the front row of pickets.