How many layers of rock and what size are required when designing overhead cover to defeat delay fuses against MM mortar fire?

To effectively defeat delay fuses against medium mortar (MM) fire, at least three layers of rock are typically recommended, with each layer needing to be at least 12 inches thick. The total thickness of the overhead cover should ideally be around 36 inches of compacted rock or similar materials. This design helps absorb the impact and mitigate the effects of shrapnel from mortar explosions. Additionally, the quality and density of the materials used play a crucial role in enhancing the protective capability.