Re: Grand Slam
Yup. 'Camouflet'. Rearrange the ground under the target, creating a void which then collapses, messing with any structures built above. Streamlined, armour piercing, fancy steel casing .. go to the memoirs to find aircrew saying they were different from other bombs, as they fell they didn't tumble, they just dropped straight down, spinning as they picked up speed.
The 4000 to 12000 lb HC "blockbuster" bombs on the other hand .... cookies! Unremarkable steel dustbins full of high explosive, often dropped in company with about 1000x 4lb incendiaries. The cookie might knock down lots of buildings, such as an entire street of houses, and the incendiaries would then set fire to the wreckage. Not nice? No. But Bomber Command learned part of its business by looking at bomb sites in the UK.