Abstract:

The application ranges of the vacuum,the vacuity,the negative pore-water pressure,the difference in pore-water pressure and the negative pressure are discussed based on the basic conception and physical characteris-tics of these items.It is concluded that(1)the vacuum and the vacuity only describe the gas state;(2)the nega-tive pore-water pressure and the difference in pore-water pressure only describe the liquid state;and(3)the nega-tive pressure can describe both the gas state and the liquid state.Moreover,it is suggested that,during the monito-ring of vacuum preloading,what is meant by the negative pressure should refer only to the negative excess hydro-static pressure for the purpose of avoiding the confusion.It is also indicated that the negative pressure is only a part of the difference in pore-water pressure.The measurement techniques and corresponding resuhs of the vacuity are finally investigated,indicating that the vacuum meter should be used to measure the vacuity under the membrane,and that the piezometer should be used to measure the negative pressure at the observation point under the ground-w ater

Key words: vacuum preloading , vacuity, pore-water pressure, pore-water pressure difference, negative pressure