──────────────┬──────────────┬──────────────┬──────────────┬────────────── Ratio of Depth│Sand and Damp │Saturated Top │ Damp Yellow │ Saturated to Width │ Top Soil │ Soil │ Clay │ Yellow Clay ──────────────┼──────────────┼──────────────┼──────────────┼────────────── 0.0│ 1.00│ 1.00│ 1.00│ 1.00 0.5│ 0.85│ 0.86│ 0.88│ 0.89 1.0│ 0.72│ 0.75│ 0.77│ 0.80 1.5│ 0.61│ 0.64│ 0.67│ 0.72 2.0│ 0.52│ 0.53│ 0.59│ 0.64 2.5│ 0.44│ 0.48│ 0.52│ 0.57 3.0│ 0.37│ 0.41│ 0.45│ 0.51 4.0│ 0.27│ 0.31│ 0.35│ 0.41 5.0│ 0.19│ 0.23│ 0.27│ 0.33 6.0│ 0.14│ 0.17│ 0.20│ 0.26 8.0│ 0.07│ 0.09│ 0.12│ 0.17 10.0│ 0.04│ 0.05│ 0.07│ 0.11 ──────────────┴──────────────┴──────────────┴──────────────┴────────────── For example, let it be desired to determine the load on a 72–inch concrete sewer with a 9–inch shell under the following conditions: depth of backfill over the top of the pipe, 15 feet; character of backfill, saturated yellow clay; superimposed load, pile of building brick 6 feet high. The ratio of the depth of backfill to the width of the trench is 15 ÷ 9 or 1.67. The coefficient in the expression _CwB_^2 is 1.39, from Table 42. The weight of saturated yellow clay is 130 pounds per cubic foot, from Table 43. Therefore the load per foot length of the sewer due to the backfill is: _W_ = _CwB_^2 = 1.39 × 130 × 81 = 14,600 pounds. TABLE 45 RATIO OF LOAD ON PIPE TO SHORT LOAD ON TRENCH[71]