A tunnel of length L = 154 m, height H = 7.4 m high, and width 6.1 m (with a flat roof) is to be constructed at distance d = 60 m beneath the ground. (See Figure 12-50.) The tunnel roof is to be supported entirely by square steel columns, each with a cross-sectional area of 960 cm2. The mass of 1.0 cm3 of the ground material is 2.8 g.(adsbygoogle = window.adsbygoogle || []).push({});

(a) What is the total weight of the ground material the columns must support?

N

(b) How many columns are needed to keep the compressive stress on each column at one-half its ultimate strength?

columns

I know that for the first question the total weight must be equal to the volume x density x gravity but for some reason I keep screwing up finding the density and the number is much too low. Am I approaching this question badly?

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# Homework Help: Elasticity problem

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