cross section configuration of the conduit is referred to as 34 truncated elliptical 34 the arch beam structure 35 is a generally planar concrete panel the panel includes a planar bottom surface 36 and a top surface defined by a pair of outwardly and downwardly inclined sides 37 thus the panel tapers slightly from its longitudinal centre outwardly toward each side thereof the thickness of the panel may be constant or vary throughout the width as required the panel is reinforced by transversely extending reinforcing rods 14 one shown or by lap spliced rods of the type illustrated in fig1 the panel is also reinforced by longitudinally extending spaced apart rods 15 and by connecting bolts 16 as mentioned hereinbefore the principal function of the rods 15 is to hold up the rods 14 during construction but they also serve to distribute loads on the panel longitudinally of the structure the other reinforcing elements described hereinbefore with reference to fig1 to 5 can also be incorporated in this embodiment of the arch beam structure the arms 38 transmit at least a portion of the arch reaction live load and overburden loads to the soil the distance each arm 38 projects beyond the side 2 of the conduit is determined by the loads to be transferred backfill material and adjacent soil strength and by the amount of confinement of side soil required further modifications and alternative embodiments of the invention will be apparent to those skilled in the art in view of the foregoing description accordingly this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the manner of carrying out the invention it is further understood.