Two identical circular tanks both with D=20 m are to be built next to each other. Both apply the same pressure q at the ground surface. a) How far do the two tanks have to be apart so that the vertical stress increase generated half-way between the two tanks at a depth of 20 m does not exceed 10% of q. Express in terms of the distance between the edges of the tanks. b) Do you expect the stress increase to be greater at any other point along the same vertical? If not, why not? If so, where do you expect it to be greater, above or below 20 m? Solve both a) and b) using the elastic solution provided in Figure 10.5 of your text book and shown below. 1, stress in percent of surface contact pressure 0.2 0.3 0.4 0.6 0.8 1.0 3 4 5 6 8 10 0.1 0 20 30 40 50 60 80 100 25 1.0 1 2.5 1.5 2 3 (0.75 6.0 7.0 4 Note: Numbers on curves indicate offset distances in radii, xir. 8.0 zir, depth in radi (9.0 21 6 (10.0 7 8 g IX 40 100 10 FIGURE 10.5 Influence values, expressed in percentage of surface contact pressure 4., for vertical stress under uniformly loaded circular area (after Foster and Alvin, 1954, and U.S. Navy, 1986)