Loads on Underground Pipes Caused by Vehicle Wheels.

Abstract

A method of computing the loads imposed on an underground pipeline by several simultaneous wheel loads acting on the surface, proposed by Spangler and Hennessey2 in 1946, and to which only a brief reference could be madei n a previous Paper1 by the present Authors, is now described in detail. A modification of that method is developed by the Authors to compensate for the nonuniformity of load distribution across the pipe breadth, which occurs in some wheel positions, and adversely affects the bedding factor for wheel loads compared with fill loads. The modification takes the form of correction factors for the conversion of the non-uniform loads to equivalent uniformly distributed loads. Their use enables the same bedding factor as that adopted for the fill load to be used for concentrated surcharge loads. Graphs of these values for the usual classes of bedding are given. The modifled method, which is applicablteo any wheel arrangement, has been used to compute the maximum loads (or load coefficients) imposed on pipes of various sizes at various depths with various beddings by:- (i) two equal wheel loads 3 ft apart (appropriate for pipes under access roads); (ii) the B.S.153, type HB, road load train (appropriate for pipes under roads, and carriageways, fields, and gardens); and the results are presented in the form of design graphs. The maximum foreseeable railway loading in England and Wales is given. It proves to be less severe than the B.S.153, type HB road loading. The design graphs may, therefore, be used for single or multiple rigid pipes of any normal size at any normal depth in trench, under roads, fields, or gardens, across railways, or under embankments, in any sort of soil and with any standard bedding and, it is hoped, will save much tedious computation.