Placement and Compaction Techniques
Thin lifts, full compaction
Placement and compaction determine density, and density drives strength, stiffness, and erosion resistance. Place loose earth in thin lifts, typically 100–150 mm before compaction, and reduce each to roughly 60–100 mm. Compact the whole area systematically, including edges and corners, where form friction and poor access cause loose zones. Use a rammer or mechanical tamper suited to the lift thickness. Keep the surface slightly rough between lifts so the next layer keys in.
Traps: thick lifts that leave loose material at the base, compacting only the middle of the wall, and adding water during compaction. Over-compaction is less common than under-compaction, but excessive tamping can shear a stiff mix or damage forms. Do not compact after the mix has begun to set.
Worked example: for a 300 mm wall, place a 125 mm loose lift, compact until the rammer leaves a firm, even surface and the layer is about 80 mm thick, then scarify lightly and place the next lift. Rule of thumb: loose lift thickness should not exceed the length of the rammer head. Test density on trial panels and compare it with the specified maximum dry density.