The effects of nearby explosions are more complex than distant explosions.
A distant explosion forms a flat impulse plane that races invisibly at supersonic speed across the air. If you are 1000 or 1200 meters from the blast, it makes almost no difference in the nature of its effects.
But an explosion up close, the explosion acts as a point source of energy dispersion. As a nearby blast rushes by a hollow cylinder like the human chest, it pushes inward at the side of first contact, then racing past squeezes the sides, and finally the back is pushed inward, and the cylinder experiences a nearly symmetrical crushing force. Remember, explosion blast waves are supersonic, >330 mm/ msec. That's passing across the width of the human chest in a millisecond or two. The US equivalent,CompB6, blasts at 7m/msec or so. The front of the chest hasn't even started to move inward from the blast in 1 msec. The Sadovsky formulas are used in blast physics. Ironically, some of the institute graduates who died on Kholat Syakl were likely skilled in this area.
In more detail, the nearby blast also spreads the surface where it first contacts - a "tearing-apart" force. Then, when the following negative pressure wave hits, it gathers together -"pinches in" the surface at the point of initial contact.
What if your head is next to the blast? Ask poor Tibo, his skull was wrecked right where the pressure first hit it, like a pane of bulletproof glass struck by a rifle round. The others had their chests torn up. The only compelling force that efficiently explains the data is a nearby explosion.
______The Mathematics Of Blowing Stuff Up
In order to make numerical assertions, it's worthwhile to use cited work in the literature. This is not to seem snooty; rather the opposite, it's to be humble enough to show sources.
My first well-connected source is Influence Of Dimensional Proportions Of Cylindrical Explosive On Resulting Blast Wave
, Robert Panowicz, Michał Trypolin, Marcin Konarzewsk, Journal of KONES Powertrain and Transport, Vol. 23, No. 4 2016 It mentions what has been known about explosions, that the effects depend only on energy and distance. It cites Sadovsky, who seems to have written the definitive work on explosions: Sadovsky, M.A., Mechanical effects of air shockwaves from explosions according to experiments, in
: Geophysics and Physics of Explosion (ed. M.A. Sadovsky), Nauka Press, Moscow 2004
Panowicz et al. offer a discussion of point-source blasts, or "a nearby explosion," which, I've suggested, was the cause of the wreckage in the den and upon the poor trekkers.
In the point detonation model approximation, the detonation process is not considered. It is only assumed that, in the initial time, in the small part of the volume, an emanation of energy occurs. The assumptions and conclusions regarding this model are presented in the studies of Taylor, Sedov and von Neumann, who developed it independently. This model was then further developed by, among others, Staniukowicz.