Solutions for settlement and consolidation of soft ground with vacuum preloading

Solutions for settlement and consolidation calculation of soft ground with vacuum preloading are studied by considering the loss of vacuum. Firstly, an axisymmetric deformation model is developed under equal strain condition according to the vacuum pressure condition of sand drain with vacuum preloading. Formulae of deformation and volumetric strain are derived from spatial axisymmetric displacement control functions by using the displacement method. Then combining the obtained volumetric strain functions and the existing Hansbo's sand drain foundation consolidation theory, and modifying some boundary conditions with vacuum preloading, analytical solutions for consolidation of soft ground under vacuum preloading are conducted when vertical water flow in soil is neglected. Finally, a comparison between the present solution and some previous solutions is made, and compared those theoretical solutions to test data in situ too. The results show that the volumetric strain has great effects on pore pressure and consolidation calculations; it would lead to large errors in consolidation calculation of vacuum preloading while quoting the volume strain formula of surcharge preloading directly. And using Hansbo's approximate method to calculate degree of consolidation can meet the requirements of precision; the calculation results are in good agreement with experimental results.