Liquefaction of cohesionless soils in the March 2, 1987 Edgecumbe earthquake, Bay of Plenty, New Zealand, and other earthquakes

Abstract

This thesis documents some of the extensive liquefaction that occurred in the sediments of the Rangitaiki Plains in the Bay of Plenty, New Zealand, as a result of the March 2, 1987 Edgecumbe earthquake, causing (along with other ground damage) about $NZ10 million damage to flood control and drainage schemes. 

Fourteen sites, ranging from sites with lateral spreading only to sites without any manifestation of liquefaction at all, were investigated with a piezocone to establish their liquefaction potential. 

Investigations led to the conclusion that five well known liquefaction prediction models utilised in this study were inadequate by themselves to predict the observed liquefaction.  Additionally, the use of poorly documented ejecta as a diagnostic tool is discussed and found to be inadequate in the identification of liquefied strata.  Despite these factors, a liquefaction mechanism was established for each of the sites studied and a ground collapse mechanism is proposed.  Lateral spreading distances and settlements were estimated and checked against various empirical models. 

Some of the sites close to the epicentres of two other earthquakes, of June 1992 and the 1977 Matata, were also investigated for these earthquakes.