Mrs P and I want to know what Vulcan Earth Anchors are.
Don't know that one in particular, but I've designed earth (and rock) anchors to tension structures against the ground, like a pile wall to support the sides of a deep excavation - you can tie the wall back by installing an anchor behind and pulling the wall back with a steel cable to the anchor.
Ooh, we may have bumped into each other in Real Life. Mrs. P*, they're lumps of metal (cast iron, stainless steel or aluminium alloy) with a hole in one end and a point on the other. As andytheflyer says a wire rope or steel bar tendon is attached to the m iddle of the anchor. Put a drive bar into the hole in the end and wallop them into the ground. Pull out drive bar, pull on tendon and the anchor flips in the ground so you can tie, eg, sheet pile walls in place. Like a toggle bolt for he ground. Vulcan is the brand my employer makes, so named because the big ones have a (slight) resemblance to a Vulcan bomber.
* "Mrs P" puts me in mind of Walter Gabriel, me old pal, me old beauty, who would address Mrs. Perkins in such a way.