Research On Wave Induced Silty Soil Liquefaction In Yellow River Estuary

When the water waves propagate over a porous sea bed, they will create effective stresses and pore water pressure,which will take dangers to offshore structures such as oil flats and submarine pipes. So it is very important to spend a lot of time and energies on doing research for seabed stability form waves.The dissertation is mainly divided into three parts. The first part of the dissertation is laboratory experiment about the silty soils liquefaction from cyclic loads. Here the devices was designed by author himself and the cyclic air pressure was used to simulate waves. During the experiment, the pore water pressure was measured by the pore water pressure collection system. At the meantime, some phenomena such as soil volcano and fluidization were observed. After the cyclic loads, subminiature static cone penetration was taken to measure the field strength of silty soils and other index of physics and mechanics was obtained by geotechnical tests.On the basis of laboratory experiment, some conclusions were drawn. These conclusions are:Field observation on the formation of sediment vertical transporting is carried out on tidal falt. Analyses of monitoring data of pore water pressure show that transportation of fines leads to development of seepage filed, and repeated liquefaction of seabed soil accelerates the adjustment of its composition and micro-structures.mathematics model with finite element solution was established to analyse the wave induced residual pore water pressure in silty soils. Dynamic triaxial data was taken to establish the relation between the cyclic numbers and pore water pressure ratio to effective stresses. For two wave conditions, the accumulation of residual pore water pressure was obtained by the calculation. Then the depth of liquefaction was analyze for different conditions according to liquefaction criteria which was first used by Zen, then modified by Luan maotian. According to the analysis the author drew the following conclusions: The seabed liquefaction depth is not to immensity but tend to a stabilization. The seabed liquefaction depth is reduceing gradually when the seabed depth increasing.The wave induced seabed liquefaction is a main attributor to forming of the submarine physiognomy in huanghe river delta.