ABSTRACT
More than 1,400 manholes were disturbed in the 2004 Niigata-ken Chuetsu, Japan, earthquake. Uplifting of sewer manholes (Figs 1 and 2) is a typical and striking damage pattern observed in developed areas after being hit by large earthquakes. The uplifted manholes not only caused the suspension of wastewater systems over a long period of time after the earthquake, but also hindered traffic flow and, in rare instances, blocked the movement of ambulances and fire engines just after the earthquake, when these were most needed. Thus, estimation of uplift displacement is an important factor to be considered for designing manholes and utility pipes under the framework of performance-based design (ISO23469 2005). Using a questionnaire survey, Honda et al. (2002) asked fire fighters about the allowable uplift displacement of a manhole to permit maneuvering of emergency vehicles. Results showed allowable displacements to be 13 cm for roads of 5 m width, and 23 cm for roads of about 16 m width (JGS 2003).
