In this study, several tests such as liquid limit test, compaction test, and XRF analysis were conducted on silty sand (SM) containing air to investigate the saturation collapse phenomenon due to flow liquefaction, which can result to the increase of the saturation degree and water content. The relationship between the flow strength and water content of the test material, which was artificially prepared by mixing Saemangeum dredged soil and water at different mixing ratios, was investigated to determine the strength variation caused by intergranular flow. When silicon dioxide (Si02) and water react with each other, energy is generated from capillary phenomenon and the attractive force between particles increases from 10% to 20% due to matric potential. The maximum flow resistance is maintained at the range of 20% to 30% water content, which is larger than the optimum water content obtained from the compaction test, so that flow resistance is greater in the region where the maximum shearing force is significantly high. However, if the water content is increased to more than 30%, the flow resistance is significantly low.

In this study, a drainage-regulated type geotextile tube structure was proposed. The structure is composed of high permeability polypropylene(PP) and low permeability (PET) fabric in which the lengths of the fabric depend on the circumference ratio of the cross section. The purpose is to reduce the pressure inside the geotextile tube structure during filling as much as possible. Experimental study on the characteristics of the geotextile tube structure according to the permeability of the geotextile was also carried out. Experimental results of 4 small scaled geotextile tube structures showed that the bottom section formed as drainage type can reduce the filling pressure as well as increase the sedimentation height which confirms as the optimum cross section of the tube.

Geotextile tubes are excellent design strategies for both shoreline protection and dewatering of fine materials. A difficulty with regard to designing geotextile tubes is the matching of the appropriate fabric with the site-specific infilled material and the unavailability of a test to determine the soil-geotextile consolidation properties. Existing methods simulate and predict the final tube shape based on the initial and final unit weights of the infill but the time required to reach the final shape or the compatibility of the infill are not being considered. This study proposes an improved hanging bag test to evaluate the compatibility of an infill with the geotextile fabric, and at the same time, to obtain the soil-geotextile consolidation properties. With the obtained consolidation properties, a big prototype simulation was possible, explaining the deformation behavior of the tube in the field. An analytical procedure used in modeling the tube was coupled with the large strain consolidation theory to simulate the filling and dewatering process.

The geotextile tube’s performance in strength, dewatering, retaining solid particles and stacked stability have been studied extensively in the past. However, only little research have been done in the observation of stress behavior of geotextile tubes. In this paper, a large-scale apparatus for geotextile tube experiment is introduced. Model tests was conducted using a custom made woven geotextile tubes. Load cells placed at the inner belly of the geotextile tube to monitor the total soil pressure. The pressure sensors are attached to a data logger which sends the collected data to a desktop computer. The experiment results showed that the maximum geotextile the soil pressure distribution varies at each geotextile tube section.

A series of injection and drainage test were conducted on an circular acrylic tube to investigate the pressure generated by the accumulated fill materials inside a circular acrylic tube structure. The acrylic tube was filled by means of gravity filling with a slurry material having an average water content of 700%. The water head during the filling process was 1.8m and the bottom pressure during initial filling was 20.18kPa. The recorded stress at the sides of the acrylic tube was 17.89kPa during the filling process and was reduced to 13.58kPa during the leaving process. Continuous drainage of the acrylic tube has greatly influenced the stresses around the tube structure. As the water is gradually allowed to overflow, the generated pressure at the topmost pressure sensor of the tube was reduced further to 2.17kPa. Eventually, the initially liquid state slurry material transforms into plastic state after water has dissipated and substantial soil particles are deposited in the acrylic tube. The final water content of the deposited silt inside the acrylic tube after the test was 42%. It was found that the state of stresses(geo-static earth pressures) in the acrylic tube was anisotropic rather than isotropic.

The acrylic tube, referred to as geocell in this paper, is 2.19m long with an inner diameter of 280mm. Both ends of the acrylic tube were covered with permeable geotextile sheets to allow water dissipation. The dredged soil fill material is hydraulically filled into the acrylic tube in the form of soil-water mixture (slurry). Load cells oriented in the vertical and horizontal directions were installed inside the geocell to measure the horizontal and vertical pressures inside the cylindrical tube. The pressure readings are collected through a data logger and interpreted by a desktop computer. The pressure distribution inside the geocell based on the load cell readings are closely related to the theoretical Ko and Ka conditions.