A rockery retaining wall is a retaining or protection structure that consists of stacked rocks without mortar, concrete, or steel reinforcement. Although the rocks are stacked in an “interlocking” pattern, there are no mechanical connections made between the individual rocks. Rather, these structures rely on the weight, size, shape, and interface friction of the rock elements to provide overall stability.
Various terms have been used to describe rockeries, including “rock breast walls,” “rockery walls”, “dry-stack walls”, “stone walls”, “big boulders walls” and “rock walls”. The terms used to describe rockeries often reflect the intended use, and, in some cases, preconceptions regarding rockeries. Some researchers have acknowledged that rockeries can serve as retaining structures and have developed equations especially designed to evaluate the stability of rockeries retaining both native soils and fills. Others practitioners have taken the middle ground, conceding that while rockeries are best implemented as decorative architectural features or as slope protection for stable slopes, there is an increasing tendency to use rockeries for stabilization of over steepened cut slopes or for retention of fill slopes. Despite the different definitions and attitudes toward rockeries, they have been successfully designed and constructed to heights up to 7.6 m (25 ft) in the Pacific Northwest and northern California over the last decade.
For the purpose of this study, a rockery is defined as an engineered system of stacked angular rocks placed without mortar in an approximate “running bond” pattern. Rock dimensions are generally greater than 450 mm (18 in) and rock weights generally greater than 90 kg (200 lb).