# My massive pile of books: How big can it get? [closed]

My heroine librarian has a fictional pile of mostly standard hardcover novels, books, etc. It is not an organized stack, it is a pile.

At what point does this either become unstable or start crushing the bottom books? It can be as wide as necessary, but I'm looking for the height at which the bottom books are still intact and usable (some day).

A magnitude of order is okay over precision measurements, because there's a variety of books, and therefore some wiggle-room.

Note: It does not have any supports (steel or shelves or anything). I will deal with how books are placed on the pile, but just imagine they're placed sloppily on the top creating a massive pile.

• Theoretically your pile could be infinitely big. Practically speaking randomly dumping on book it will probably get to 2 meters max before books start falling back off. – Bellerophon May 7 '16 at 20:31
• A very difficult question! However, googling stuff reveals that the breaking length, the length of paper that will break under its own weight, for news print is 3.7km. I think other factors will come into play, moisture? beatles? before shear weight of books is a problem – Ewan May 7 '16 at 21:10
• I think Ewan inadvertently nailed the limiting factor: "shear" weight--a book getting crushed because half of it is supported on another book but the load gets applied to an unsupported part of the book. What that limit would be I do not know, though--but I rather suspect it's within the range that a DIYer could test. – Loren Pechtel May 7 '16 at 22:50
• If you're looking only at the crush weight--there's a guy on You-Tube that has a series of videos where he's crushing various things with a hydraulic press. One such video is crushing a book. He probably knows the force it took. – Loren Pechtel May 7 '16 at 22:51
• I fail to see how is this about worldbuilding at all. We might be able to answer it, but that does not mean that here is the place for such question. – clem steredenn May 9 '16 at 10:30

The issue isn't crushing or "infinite in theory". The practical issue is the limit set by random effects, variations in book positioning (if "sloppy"), and most of all irregularities in books themselves.

A pile is stable so long as its centre of gravity (CoG) is over the start of the pile and dynamic effects of oscillations/vibrations, wind, human touch etc don't cause its CoG to not be over the centre (of momentum to build up etc).

The taller it is, the more all those can play a role. Book sides aren't exactly parallel; books act like elastic springs when other books in the pile move, wind and touch increasingly cause instability. Above all, when the pile oscillates, the higher up books move sideways as a unit much more (and elastic/dynamic effects become more pronounced which amplifies any existing/initial oscillation), and it also only needs an increasingly small maximum tilt during an oscillation to reach tipping point.

I don't have an answer but that's what will limit it, however careful your hero is.

• Sub answer: shorter than a tree, because a tree is using the same materials, but with far more care to the structural orientation of its cells and fibers! – Cort Ammon May 8 '16 at 18:35
• @CortAmmon "It can be as wide as necessary" – PyRulez May 8 '16 at 23:35
• All you're showing is that her pile of books will spread out. That's not a limit on the height. – Loren Pechtel May 9 '16 at 2:32

What you may notice is the book doesn't actually crush, but rather it (somewhat explosively) displaces from under the press.

The practical implication of this is that there's no practical limit to the number of books in your pile that's within a humanly understandable range of numbers.

• You're going to have damage to the covers of hardbacks

• There's going to be shear damage to books on uneven surfaces. A larger book on two books of different thicknesses will be cut in half by the load.

• Old books with hard glue in the spines will be damaged, but reparable.

If the books are all the same thickness, carefully stacked into a pyramid, there can be more books than can be handled by one unassisted person in a lifetime.

If they're just chucked in any old how (she should treat her books better!) then there's an ISO 9895 to help you.