Abstract:

The pressure drop of fluid in the prefabricated vertical drains (PVD) in vacuum preloading ground was analyzed based on the pressure-drop theories of ascending one-phase flow and two-phase flow. An experimental in-vestigation into the vacuum pressure of fluid in the PVD was then conducted. The results show that the fluid pres-sure in vacuum preloading ground gradually decreases along the flow direction , that only the fluid above the null groundwater pressure surface during the vacuum preloading is of a vacuum pressure because it is the only pore pres-sure reduction instead of the vacuum pressure of fluid under the null surface , that the vacuum pressure of fluid and the pore pressure reduction are two different conceptions , that the total pressure drop of the fluid in the vertical drains in vacuum preloading ground mainly includes two parts , namely the pressure drop due to the friction resis-tance and that due to the gravity , the latter being the inherent pressure drop of fluid in vertical direction , and that the falling depth of the null groundwater pressure surface directly embodies the intensity of vacuum preloading.

Key words: soil mechanics, vacuum preloading, vertical drain, two-phase flow, pressure drop