An explosion creates a pressure wave. A pressure wave fractures rock. Fractured rock may be easier to pierce than solid rock.
Ergo, if first bunker buster penetrates to maximum depth -20m and then explodes, fracturing rock within a __ radius, then second bunker buster travels through that fractured rock, the second (and so on) may be able to penetrate deeper.
I have no idea about the physics of penetrating fractured vs non-fractured rock, but it's a physically plausible mechanism.
Furthermore, given the multi-minute timeline reported, there's enough time for the bombs to be deployed sequentially.
In the linear case a bomb twice the size goes twice as deep.
Take a bomb, cut it in half and drop each half separately, one after another into the same hole, would you except the cumulative depth to be greater than the whole bomb or less? Consider that in the case of the whole bomb it is equivalent to two halves arriving at the exact same time.
Ergo, if first bunker buster penetrates to maximum depth -20m and then explodes, fracturing rock within a __ radius, then second bunker buster travels through that fractured rock, the second (and so on) may be able to penetrate deeper.
I have no idea about the physics of penetrating fractured vs non-fractured rock, but it's a physically plausible mechanism.
Furthermore, given the multi-minute timeline reported, there's enough time for the bombs to be deployed sequentially.