Interlocking compressed earth blocks (ICEBs) are machine-pressed soil blocks that stack together like toy bricks, without mortar. They offer a low-cost, low-carbon way to build houses in earthquake-prone regions. Laboratory testing of ICEB walls remains rare because full-size tests need large and costly equipment. Testing small models instead would solve this problem, but only if clear rules exist to make the small model behave like the real wall. Such rules, called similitude rules, do not yet exist for dry-stacked interlocking earthen walls, because these walls act through friction and interlocking between blocks rather than as one solid material. This paper derives the missing rules using dimensional analysis. Three ratios must be matched between model and prototype: the friction between block faces, the ratio of key strength to friction resistance, and the ratio of vertical load to block strength. The paper shows how to correct the reduced self-weight of a small model with added weights, how to correct for size effects, and how to press model blocks in 3D-printed moulds. A quarter-scale worked example based on published test data requires only a 37 kg added weight and one sixteenth of the lateral testing force.

Compressed earth block, Dimensional analysis, Dry-stack masonry, Scale modelling, Similitude.