Abstract
The projection of sewerage manholes above ground has been observed during earthquakes that have caused significant soil liquefaction. The force that moves a manhole upward can be attributed to the buoyancy caused by the liquefied soil, since no other reasonable causes are apparent. The weight of the manhole and the soil resistant force are the only forces that are in static equilibrium with the buoyancy. In this paper, we discuss the quantitative conditions for the possible projection of a manhole taking into consideration the above equilibrium of forces. The results should provide information helpful in the planning of countermeasures against damage to sewerage systems caused by projecting manholes.
