STRENGTH llEQUIREMENTS FOR ROUND CONDUIT 



747 



depends on the characteristics of the undisturl)ed soil. A comparison of 

 the values obtained from a 5-inch wide trench dug in sandy clay (typical 

 Chester, N. J. soil) and trenches between 18 and 30 inches wide shows 

 that the values for 5-inch width are greater than for an 18- to 30-inch 

 width when using sand backfill, and less when using clay backfill. 



(Text continued on page 750) 



SAND BACKFILL 



4 



LOADING CONDITION 





i 





F= 10,000 LBS 



18 



CLAY 



ei= MEASURED STRAINS [iN/INJ 

 E • IOxlO« PS I 



Fig. 8 — Moment distribution in a thin-walled tube, using sand backfill. 



