ABSTRACT
What is the minimum stress, sx of the pipe against the soil in order to prevent inward collapse of the pipe wall? Because the soil is clay, s1 - s 3 = 2c = 840 lbft2. But s1 = 130(10) = 1300 lb/ft2. At active soil resistance, s3 = s x = 1300 - 840 = 460 lb/ft2
At passive soil resistance, sx = 1300 + 840 = 2140 lb/ft2
PROBLEMS
4-1 What is the vertical effective (intergranular) soil pressure at the level of the top of a pipe if the water table is 17 ft above the top of the pipe and the soil surface is 47 ft above the top of the pipe? The soil is dune sand for which: G = 2.7 = specific gravity of grains, e = 0.7 = void ratio, S = 0.1 = degree of saturation of soil above the
water table. (4.11 ksf)
4-2 What is the maximum principal stress s1 acting vertically at soil slip in granular soil if horizontal stress is 600 gr/cm2 and if j = 30o? (1800 gr/cm2)
4-3 What is the maximum principal stress acting vertically at failure in clay if j = 0, s3 = 4000 Pa acting horizontally, and cohesion is c = 2800 Pa?
