Abstract: An erosion protection unit (7), comprising a tetrahedral frame comprising six outer elongate members (9) arranged in the outline of a tetrahedron, and a triaxial central strut arrangement (11) comprising three struts (13, 15, 17) arranged mutually perpendicular to one another and passing through the geometric center of the tetrahedron, such that each outer member is braced by a strut passing from its center to the center of a second opposite outer member.

Abstract: A flexible blanket for protection or stabilization of underwater structures and pipe lines, unstable beds and embankments, comprising a plurality of segments (1) arranged in one or more layers (10) each one segment in height, the segments of the or each layer (10) being disposed substantially contiguously at least at a median zone (2) of their height dimension, each segment (1) tapering substantially regularly from a maximum cross section at said medium zone (2) to a minimum cross section at one or both ends thereof, and each segment being so bonded to each adjacent segment in the region of their respective median zones that the segments are held substantially contiguously but are free to pivot relative one to another about the bond in so far as is permitted by said taper, the arrangement of the tapers being such that each segment is capable of pivoting with more than one degree of freedom.