真空预压中真空度及其测试和分析

基于真空、真空度、负的孔隙水压力、孔压差和负压的基本概念及其物理特性，讨论了这些物理量的适用范围，即真空和真空度用于描述气体状态、负的孔隙水压力和孔压差用于描述液体状态、负压既可描述气体状态也可描述液体状态，并建议在真空预压监测中负压仅指负的超静孔隙水压力，以免混淆。同时指出，负压与孔压差并不相同，孔压差包含了负压。文中还探讨和分析了真空度的测试技术及测试结果，实测结果表明，测试膜下真空度宜用真空表，测试地下水位以下测点的负压则宜用孔压计。

Measurement and Analysis of Vacuity Under Vacuum Preloading

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 characteristics of these items. It is concluded that (1) the vacuum and the vacuity only describe the gas state;(2) the negative pore-water pressure and the difference in pore-water pressure only describe the liquid state; and (3) the negative pressure can describe both the gas state and the liquid state. Moreover, it is suggested that, during the monitoring of vacuum preloading, what is meant by the negative pressure should refer only to the negative excess hydrostatic 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 results 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 groundwater.