真空预压地基竖向排水体内流体的压降分析

基于上升单相流与两相流压降理论,分析真空预压地基竖向排水体内流体的压降规律,再根据真空预压地基排水体中流体真空度的现场试验,得到以下结论:真空预压地基内流体的压强沿流体运动方向逐渐减小;真空预压期间只有地下水相对压强为0的压力面(零压力面)以上的流体才有真空度,零压力面以下地基土体中只存在孔隙压力下降,流体不存在真空度;孔隙压力降低与流体真空度是完全不同的两个概念;真空预压地基竖向排水体内流体的总压降主要包含重力压降和摩阻压降,重力压降是流体在竖直方向的固有压降;抽真空期间竖向排水体内零压力面的降低深度是真空预压强度的直接体现.

Analysis of Pressure Drop of Fluid in Prefabricated Vertical Drains in Vacuum Preloading Ground

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 investigation into the vacuum pressure of fluid in the PVD was then conducted. The results show that the fluid pressure 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 pressure 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.