Strength in pounds per linear foot to carry loads from ditch filling material such as ordinary sand and thoroughly wet clay, with the under side of the pipe bedded 60° to 90° by ordinary good methods. From Proc. Am. Society for Testing Materials, Vol. 20, 1920, page 604. ────────┬────────────────────────────────────────────────────────────── Height │ of Fill │ Above │ Top of │ Pipe, │ Feet │ Breadth of the Ditch a Little Below the Top of the Pipe ────────┼───────────┬───────────┬───────────┬────────────┬───────────── │ 1 Foot │ 2 Feet │ 3 Feet │ 4 Feet │ 5 Feet ────────┼───────────┴───────────┴───────────┴────────────┴───────────── │ Ditch Filling Material ────────┼─────┬─────┬─────┬─────┬─────┬─────┬─────┬──────┬──────┬────── │sand │clay │sand │clay │sand │clay │sand │ clay │ sand │ clay ────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼──────┼──────┼────── 2│ 265│ 280│ 615│ 635│ 970│ 990│ 1330│ 1,350│ 1,690│ 1,710 4│ 400│ 450│ 1055│ 1125│ 1745│ 1825│ 2455│ 2,535│ 3,165│ 3,250 6│ 470│ 545│ 1370│ 1500│ 2370│ 2525│ 3405│ 3,575│ 4,460│ 4,740 8│ 505│ 605│ 1600│ 1790│ 2875│ 3115│ 4215│ 4,495│ 5,595│ 5,890 10│ 525│ 640│ 1765│ 2015│ 3275│ 3610│ 4900│ 5,295│ 6,590│ 7,020 12│ 535│ 660│ 1880│ 2185│ 3600│ 4030│ 5485│ 6,000│ 7,460│ 8,035 14│ 540│ 675│ 1965│ 2320│ 3855│ 4380│ 5975│ 6,620│ 8,225│ 8,950 16│ 545│ 680│ 2025│ 2425│ 4065│ 4675│ 6395│ 7,165│ 8,890│ 9,775 18│ 545│ 685│ 2070│ 2505│ 4230│ 4920│ 6750│ 7,630│ 9,480│10,520 20│ 545│ 690│ 2100│ 2565│ 4365│ 5130│ 7050│ 8,060│ 9,995│11,190 22│ 545│ 690│ 2125│ 2610│ 4470│ 5305│ 7305│ 8,425│10,445│11,795 24│ 545│ 690│ 2140│ 2645│ 4560│ 5445│ 7525│ 8,750│10,840│12,340 26│ 545│ 690│ 2150│ 2675│ 4630│ 5575│ 7705│ 9,035│11,185│12,830 28│ 545│ 690│ 2160│ 2695│ 4685│ 5680│ 7860│ 9,280│11,490│13,270 30│ 545│ 690│ 2165│ 2715│ 4725│ 5765│ 7990│ 9,500│11,755│13,670 Very │ │ │ │ │ │ │ │ │ │ great │ 545│ 690│ 2180│ 2770│ 4910│ 6230│ 8725│11,075│13,635│17,305 ────────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴──────┴──────┴────── =92. Cement and Concrete Pipe.=—Although there is no general recognition of a difference between cement and concrete pipe, there is a tendency to term manufactured pipe of small diameter cement pipe, and large pipes or pipes constructed in place, concrete pipe. Cement, unlike clay, is used in the manufacture of pipe in the field or by more or less unskilled operators in “one man” plants. Great care should be used in the selection of cement, aggregate, and reinforcement for precast cement pipe since the shocks to which it is subjected in transit are more liable to rupture it than the heavier but steadier loads imposed on it in the trench.