The weight of the earth, as well as surface loads above the pipe, produce soil pressure on the pipe. The weight of the earth or "earth load" is often considered to be a "dead-load", whereas surface loads are referred to as "surcharge loads" and may be temporary ("live loads") or permanent. When surcharge loads are of short duration they are usually referred to as "transient" loads." The most common live load is vehicular load. Other common surcharge loads include light structures, equipment, and piles of stored materials or debris. Design procedures and formulas are available for calculating the vertical soil pressure due to both earth and surcharge loads, which may then be used for calculating deflection and for evaluating the pipe's vulnerability to wall crushing and buckling.
Schematic of Pipe Trench Cross Section