Investigation Dynamic Properties of Soil (The Damping Ratio and Shear Modulus) for Resistance Design at the LNG Bac Lieu Gas Pipeline Project by Cyclic Triaxial Test

The LNG Bac Lieu gas pipeline project is part of the 3.200MW LNG power plant complex in Bac Lieu province. The entire pipeline will be designed underground at the sea floor to be directly subjected to dynamic loads (earthquakes, waves ...). Soil response to dynamic loads is measured by the soil's dynamic properties such as dynamic strength, shear modulus and damping ratio. These soil parameters are very significant to study the movement of the ground as well as the local reaction of soil sediments under the effect of loads and cyclic soil structure. Therefore, it is very important to investigate the earth's dynamic properties (dynamic strength, damping ratio and shear modulus) to design seismic resistance for this project. From the relevant literature, it is known that the dynamic properties of the soil are influenced by the soil type and the position of the soil structure. 6 soil samples were examined randomly at different depths to determine soil properties. When studying dynamic strength, people often use direct test methods such as torsion cutting, cyclic flat cutting and cyclic triaxial test to determine the dynamic strength (dynamic resistance) of the soil. In which, the cyclic triaxial test method allows the simulation of real-world conditions to be easily simulated. The results of applying this method to soft clay and clay phases show that the damping ratio is 0.117-0.162D, the average is 0.136D, the shear module is 1650-2632kPa, the average is 2141kPa.