Dynamic Characteristics Of Shallow Gas Seabed Under Wave Loading

Shallow gas is widely found in the Hangzhou Bay,the Pearl River Estuary,the East China Sea and the South China Sea shelf area.The pore pressure is oscillated and grew,the effective stress decreases under the wave loading,what's worse,it can also lead to geological disasters such as liquefaction and seabed instability.Based on the basic physical property and composition of the sand sampled in the Hangzhou Bay area,the remolded sand samples are prepared.The dynamic behaviours test and numerical simulation of the seabed under wave loading are carried by the GDS dynamic triaxil experimental system and the FLAC3 D software.The main contents are as followings:(1)The current research status and methods are summarized,including wave loading theory,soil dynamic behaviours under cyclic loading,gassy soil,etc.The wave theory,wave loading formula and the judgment criterions of seabed liquefaction under wave loading are discussed.The Biot consolidation theory of mechanical response of seabed is expounded.(2)The gassy sand samples with different saturation are prepared by the high pressure dissolved gas saturation meter,and the dynamic behaviours test of the gassy sand under the sine wave loading of different amplitude are carried by using the GDS dynamic triaxil experimental system.The results are analyzed from the time history of pore pressure,the dynamic pore pressure stress model,the dynamic pore pressure strain model,the effective stress path,and dynamic stress-strain relationship.(3)Based on the stress,strain,pore pressure and other data obtained by the dynamic triaxil experiments,the performance of the hypo-plastic bounding surface model is tested,then its parameters are calibrated,which are used in the numerical simulation.(4)Based on the hydrological data in the sea area of Hangzhou Bay,the pore pressure and the effective stress change process of the shallow gassy seabed under wave loading are calculated and analyzed by FLAC3 D software,and the liquefaction rules of the gassy seabed is discussed.The numerical simulation results are in agreement with the experimental data.