Abstract
On the vacuum-induced consolidation method which is one of the soft ground improvement methods, resolved air and gas are pumped out mixing with ground water through prefabricated vertical drain (PVD) and horizontal drainpipe due to vacuum pressure. This method is the accelerated consolidation method. It is necessary for the practical design to evaluate the increment in consolidation pressure suitably. Therefore it is one of the most significant problem to make clear the mechanism that the flow pattern and pressure in PVD are changed in the cause of air and gas. A sample pumping test system is developed which simulates the condition of flow in cylindrical vertical drain, in which can be controlled the shape and volume of air, measured the pressure and visualized the behavior of flow, in the riser pipe under the negative pressure. This paper discusses the flow pattern and pressure in the riser pipe. Practical parameters to evaluate above phenomena are proposed, and the validity of parameters is confirmed based on the experimental results.
