Wild guess here: But isn't it only the end panel that gets the critical stresses for analysis?
The interior panel loads are balanced by the opposing forces from the other side - and if one panel area is empty and its neighbor is filled, then the empty panel must act like an "end panel." Therefore, every intermediate panel division must be fully capable of holding an end=panel's load.
The load against the end panel is going to be transmitted at a 30 degree from the horizontal because that "angled row" of pipes goes up at 30 degrees from the bottom. Assume every pipe is going to roll on the one below it as if it had no friction. Then, at 30 degrees from vertical, the maximum side force is going to be developed. Add up all the side forces at each 30 degree "slant"
Rows 1 through row 6 have 7 pipes in the "slant row"
Row 7 has 5 pipes x wt/pipe x cos 30.
Row 8 has 3 pipes x wt/pipe x cos 30
Row 9 has 1 pipe x wt/pipe x cos 30.
(Cos 30 x wt/pipe because some of the weight of each pipe is carried down and some sideways at the 30 degree point where it "touches" the support pipe below.)
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I strongly suspect, but really don't know, that a "real" quarry or "chute and solids" engineer who works with gravel and stone transportation in vertical conical-bottom tanks would know how to approximate this.