of of

Let the bottom of the excavation be h ft above the top of gravel layer. Now the downward pressure acting at the top of the gravel layer is

(J'e = yth = 110.62h Ib/ft2

= 3070 lb/ft 2

Now, 110.62h = 3070 or h = 3070 = 27.75 ft 110.62

Depth of excavation, d = 39.4 - 27.75 = 11.65 ft

This is just the depth of excavation with a factor of safety F s

= 1.0. If we assume a minimum F

s = 1.10

h = 3070 x 1.1 = 30.52 ft 110.62

Depth of excavation = 39.4 - 30.52 = 8.88 ft

Example 5.13 The diameter of a clean capillary tube is 0.08 mm. Determine the expected rise of water in the tube.