Test Invertigations Of The Permeability Behavior Of The Soft Clay In The South China Sea

In the South China Sea, there are widely distributed with a layer of soft clay, it’s thickness is about1～20m. This layer of clay presents these characteristics:high compressibility, high void ratio, low permeability and high water content. Most of these clay are in the lack of consolidation state.The marine engineering character of this clay is so poor, without drainage consolidation or any otherway to treat it, it is not suitable for any engineering.This paper investigates the permeability behavior of the soft clay in the South China Sea. The hydraulic conductivity of marine clay is a key parameter in the design of near shore works. It is understood that the hydraulic conductivity of marine clay is influenced by many factor, but the most important factors are consolidation pressure and void ratio,threrfore,the research to the permeabiliy of the marine clay is very necessary. However, there are no available test results of the hydraulic conductivity for the marine clay in the South China Sea. In this study, the engineering properties of the soft clay are analyzed with laboratory tests and scanning electron microscope. The hydraulic conductivity is measured by using a modified conventional triaxial apparatus. Trial tests are first conducted to determine the pore pressure difference suitable for the measurement of hydraulic conductivity. Then five tests are performed to measure the hydraulic conductivity of the marine clay in the South China Sea under an isotropic consolation pressure from40kPa to450kPa. It is found that the relationship between the logarithm of hydraulic conductivity and void ratio is approximately linear. The hydraulic conductivity decreases from about10-9m/s to about10-10m/s with the decrease of void ratio from about1.6to about0.9. At the same time, contrast the descent rate of the permeability, it can be found that before the140kPa consolidation pressure the permeability coefficient drops quickly, after140kPa the drop rate slowed down gradually, until basically does not change,At the same time,void ratio in the period also drooped to0.9～1.0,the change rate is very slow. therefore, can determine the clays consolidation process occurs mainly before140kPa consolidation pressure.