1) A mine is dug 3 km beneath the earth, a shaft is then sent off to the side. What is the stress being exerted on a 1 x 1 meter square of roof given an average rock density of 2800 kg/m3?
2) In another area of the mine the roof is sloped at 30 degrees. For a 1 x 1 meter square section of sloped roof what is the normal stress it is undergoing? The shear stress?