Abstract: A vertical drain for draining fluid from ground soil, which drain comprises an elongate core having one or more channels extending along the length of the core to receive fluid; electrically conductive means extending substantially along the length of the core; and a filter surrounding the core, wherein fluid from ground being consolidated passes through the filter into the one or more channels in the core.

Abstract: An interlocking joint for linking sheets attached to or incorporating the joint together in a sealed manner to form a screen, the joint comprising a hook portion extending substantially along the length of a free edge of the joint, a rib portion extending substantially along the length of the joint adjacent the hooked portion and a hook receiving portion, the hooked portion and the ribbed portion defining a first space therebetween and the hook receiving portion and the rib portion defining a second space therebetween, wherein the shape of the first space substantially corresponds to the shape of the ribbed portion and the shape of the second space substantially corresponds to the shape of the hooked portion such that the interlocking joint can slidably receive a substantially identical interlocking joint.