Study On Numerical Simulation The Response Of Shallow Sea Soil Around The Bucket Foundation Under Dynamic Loads

There are more and more energy demands in the world, while the traditional energy is exhausting, the oil/gas exploitation gradually develops into the deep-sea area. Traditional platform and foundation are difficult in installation and use for deep-sea oil/ gas exploration. Therefore, the new platform and foundation are developed, such as bucket foundation. Current study on bucket foundation is still not intensive enough, especially on dynamic responses. So the study on the liquefaction, softening and deformation of bucket foundation and the surrounding soil layer under dynamic load is necessary.In this thesis, the background is introduced to present the advance and key problems firstly. Dimensional analysis of the controlling parameters in the physical processes and definitions of the constitutive model are conducted secondly. The behaviors of ground soil(sand and clay) of bucket foundation under dynamic loads are simulated by using FLAC3 D software. The results show that:(1) The shear modulus and internal friction angle(sand), cohesion(clay), permeability coefficient, dynamic load, frequency, barrel diameter are the controlling parameters, affecting the developments of the soil deformation and liquefaction.(2) The smaller soil shear modulus, smaller diameter of the barrel, the higher load frequency make the soil deformation and liquefaction easier. The changes of liquefaction is little with the variations of the internal friction angle and permeability coefficient of sand. The smaller soil internal friction angle,the higher permeability coefficient also make the soil deformation easier.(3) The smaller soil shear modulus, cohesion, and dynamic load, the higher load frequency, the smaller diameter of the barrel lead to a greater super pore pressure ratio in clay. Changing the permeability coefficient has little affect on the super pore pressure ratio in clay. While changes in shear modulus, barrel diameter, dynamic load and the load frequency, cause the vibration of the soil mass range is larger, but the accumulation of displacement quantity is not obvious. When cohesion greater than a certain value, the clay of super pore pressure ratio and displacement time history curve.(4) Soil liquefaction or softening around the bucket foundation under dynamic load, appears only in a certain area(sand in this study case about barrel height 1 to 2 times the distance, the clay for 1 to 2.5 times) and not the whole area, the distribution of belt. And the influence of the sandy soil along the depth direction(sand in this study about the barrel height), the influence of clay along the depth is limited.