The analysis of efficiency of suction drain method by step vacuum pressure

Abstract

The purpose of this study is to present suction drain method as an alternative to the existing consolidation acceleration method and to perform a series of tests, varying types of step suction pressure conditions in order to assess the characteristics of improvement of suction drain method. The settlement occurred during the test and the impacts of water content lowering phase and strength increment after the completion of the test, the degree of consolidation depending on the duration of improvement were evaluated to determine the most influential factors for suction drain method under different conditions. The test result indicated that the degree of improvement increased more when the duration to the final step suction pressure (-0.8kg/cm 2) was shorter INTRODUCTION Although vacuum consolidation method was suggested as an alternative to the existing consolidation acceleration method (Kjellman, 1952), many problems have been identified. High prices of sealing sheets which are provided to maintain suction pressure, frequent breakdowns during installation, and the reduced efficiency of vacuum pump due to the long operation hours are some of the many problems identified. It becomes evident that there is a growing demand for a new consolidation acceleration method which can solve a weak point and problems noted from the existing methods. Suction drain method presented in this study is highly effective method to improve the suction pressure efficiency by pressuring drain directly through the installation of vertical drain into the ground. Unlike the existing displacement method by preloading or vertical drain method, suction drain method does not require a surcharge load. It is also effective to solve many problems which were noted from vacuum consolidation method by connecting the drain with the vacuum hose directly. Therefore, it can be the best method to improve thick soft ground. It is true that not many hard studies were conducted to on the influential factors of suction drain method so far.