The on-site quality control of armourstone during construction of a rock revetment in south Devon, UK

Abstract

A programme of on-site quality control of the as-produced properties of rock armour used for the construction of a beach revetment for coastal protection in south Devon is described. The programme was based on guidelines set out in the recently published CIRIA/CUR Manual,The Use of Rock in Coastal and Shoreline Engineering (1991). The results of the study indicate that the quality control of heavy armourstone block weight, grading and shape would be greatly facilitated by the introduction of standard specifications as recommended in the CIRIA/CUR Manual. A completely satisfactory test for the quality control of block integrity has yet to be devised and accepted, although the drop test breakage index described in the Manual provides a starting point. An improved method of heavy armour block weight estimation by ‘cubing-up’, based on the volume of an imaginary enclosing rectanguloid multiplied by the rock density and a fractional weight shape factor, has been developed. Using shape factors computed from weighed sample blocks of known density, the accuracy of these block weight estimates is shown to be in the order of ±5% for mean or median values. These fractional shape factors also allow some control of possible undesirable block shapes, such as the rectanguloid or wedge shape.