Abstract: In order to solve the inclined problem of the ancient seawall, the earth pressure on the ancient seawall with different types of backfills are observed based on the in-situ test. Three types of ancient seawall are filled with different backfills as the foamed cement banking (FCB), natural soil and shale ceramisite respectively. The law that the earth pressure changed with time is analyzed, also including the distribution of the earth pressure and the location of resultant force point. The unloading effects of the three different filled materials are discussed. The distribution of earth pressure is nonlinearly folded at different levels in the middle of the wall. The earth pressure is higher in the middle and lower at the both top and bottom of ancient seawall. The height of actual action point of earth pressure resultant from field measuring is 0.42-0.49 times of the wall height which is upper than the theoretic calculating result. FCB is an effective unloading filled material used to decrease the pressure on the ancient seawall that it can reduce the earth pressure and overturning moment by 33.1% and 41.4% respectively comparing with undisturbed soil.

Key words: earth pressure, action point of earth pressure resultant, load reduction, ancient seawall, field test