A cantilevered retaining wall can be constructed in a variety of ways. it may be a gravity cantilevered wall or a nongravity cantilevered wall. The difference is that the gravity cantilevered wall is roughly shaped in cross-section like an upside-down 'T' (sometimes called a semigravity wall). The other type is shaped like an 'I' in cross-section.
Gravity walls (including semigravity walls) are generally cast-in-place concrete.
Nongravity walls may be comprised of continuous or interlocking elements such as sheet piles or secant piles, or they may have discrete vertical elements, such as H-piles, with horizontal panels or planks (lagging) spanning the distance between adjacent vertical elements.
In Sheeting, a cantilvered wall is a wall with no external supports. It is driven into the ground and the soil is excavated. The wall is suported by cantilevering above the excavation line. This is typically limited to excavation depths of 15 feet or less. As the excvation proceeds deeper the sheeting must be braced at certian depths. The support may be braces in front of the excvation, or anchors installed through the sheeting and founded in the retained soil.
Lagging refers to the type of wall design. Sheeting can be steel sheet piles which are Z shapes when locked together form a couragated wall, or soldier pile and lagging. This consists of piles driven at some distance apart, typically 8 feet, along a wall line. As the excavation progresses, wood boards,2- 3 " thick 8" wide are inserted betweeen the flanges of the piles, forming a solid wall. Either wall system can be cantilevered anchored or braced.