ABSTRACT
Perhaps the simplest underground structure is the buried pipe conduit of relatively small dimensions, used as a passageway for fluids, gases or various types of cables. The walls of these pipes have in the past been made thick enough for the structure to be considered as rigid, so that failure under high surface loading is associated with bending of the cross section, rather than by buckling or compression. In general, pipes made from concrete and cast iron are termed ‘rigid’, whereas thin-walled pipes made from plastic, steel sheet or corrugated metal sheet are considered ‘flexible’, and are more likely to fail by buckling of the pipe wall. There is, of course, a transition between rigid and flexible construction, and this will be discussed later. This chapter will concentrate on the existing analysis and design rules for thick-walled pipes and conduits, which are governed to a large extent by the way the pipe is bedded in the soil, by the properties of the soil and by the method of backfill.
