Revetment

In permanent fortification, is a retaining wall of masonry built for the purpose of holding back the earth of which works are composed. The most ordinary position of revetments is for the escarp and counterscarp of the ditch. The most important of these two is the escarp, which has to hold back the great ma of earth represented by the rampart, parapet, banquette, etc. It is usually of solid brick-work or stone, 5 feet thick at the top, and sloping outwards as it descends (on the ditch side only) to the extent of 1 in 6. Prior to Vauban’s time, the escarp revetment was commonly raised to the top of the parapet; but as in this case the artillery of a besieger played on the top of the wall, and ruined it soon after the siege commenced, that engineer adopted the principle—thenceforth followed—of raising it no higher than the crest of the glacis, or about 7 feet above the natural ground, leaving the parapet above of sloped earth only. When the main ditch is 24 feet deep, the scarp revetment will be about 30 feet high. Additional strength is imparted to the revetment wall by ma ive buttre es at every 15 feet, called counter-forts , and these again are sometimes connected and strengthened by masonry arches outside the revetment. The revetment forms a terrible barrier to an a aulting party. In field-works temporary revetments may be made of timber, turf, hurdles, or any other materials on hand.