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peri

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**[SOLVED] Pressure on walls of granite shaft**

## Homework Statement

A friend said "In the deeper mines rock can literally explode if struck or impacted b/c of the pressure of the rock above it." This brought to mind the formula for hydrostatic pressure and nothing else. The density of granite is given as 2.75 g/cm^3. I want to find the pressure the rock is under at the bottom of a 1,000 foot mine shaft.

## Homework Equations

P = rho * g * h + Pa

## The Attempt at a Solution

Google can verify:

(2750 kg/m^3)*(9.8 m/s^2)*(1000 feet) + (101,325 Pa) is 1,206 psi.

I know bed rock has sizable voids because there are aquifers, caves and caverns; further assuming there are voids on smaller scales the density of granite could be seen as an upper bound -- I would expect granite chunks to

*just*float in a liquid with a density of 2.75 g/cm^3. Given this insight I decided that hydrostatic pressure probably sanely gives an upper bound. Was I right?

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