Effect Of The Salinity Field On The Sediment’s Consolidation Process In The Yellow River Estuary

Every year, approximately hundreds of millions of tons sediments discharged into the Bohai Sea from the Yellow River, of which more than 80% sediments deposits around the estuarine delta. The Yellow River runoff, have remarkably affected the salinity of Yellow River Delta. At present, the deposition process of sediment in different salinity environment has been basically clear. However, the consolidation of sediment is not clear. Jointly supported by the National Natural Science Foundation of China "Effects of the salinity on the deposition and consolidation and erosion process of inputing sediments in the Yellow River estuary" (Contract No.41372287; Awarded:2014-2017) and "Investigation of sources and governing factors of seabed erosion and resuspension in Yellow River estuary" (Contract No.41272316; Awarded:2013-2016), this dissertation reveals the effect of the salinity field on the sediment’s consolidation process.The salinity field of Yellow River Delta is divided into several areas based on the relevant data. And the relationship between salinity and sediment properties is analysed. Two consolidation test for the Yellow River delta sea sediment under different salinity of sedimentary environment in field are conducted. At the first test, the value of penetration resistance and shear strength in the process of consolidation under different salinity sedimentary environment are recorded. Soil sample are taken from each trial pit for salinity test at the beginning and the end of the field test. As a result, the value of the salinity of the soil sample in obtained. At the second test, the value of penetration resistance and pore water pressure in the process of consolidation under different salinity sedimentary environment are recorded. Undisturbed soil sample and tubular soil sample are taken from each trial pit for soil test in laboratory and salinity test. Then, the moisture content, density and salinity of the soil physical parameters are obtained.Main findings are demonstrated as follows:1) The salinity field around the estuary is divided into north, northeast, east and south. The salinity values, from big to small, is north, northeast, east and south. The moisture content, void ratio, compressibility and cohesion increase with the increase of salinity. The saturation, plasticity index and internal friction angle reach great value with the increase of salinity. The density of sediments and the plastic index reach the minimum value with the increase of salinity.2) The consolidation process is obviously different under different salinity of sedimentary environment. When the salinity value is less than 20‰, the influence of salinity value on new sedimentary soil consolidation strength and consolidation rate is not significant. After more than 20‰ salinity values, new river estuary sedimentary soil strength of consolidation and consolidation speed variation characteristics as follows:the sedimentary environment of every increase 1‰ salinity values, the maximum sediment penetration resistance strength ratio increased 0.15 times, the maximum rate of sediment consolidation ratio increased 1.23 times. As the salinity higher, so the thickness of sediment thicker.3)The salinity of the sedimentary environment influenced consolidation the most obviously at the first two days. And the most obvious value between 20‰ and 24.67‰, the sediment pore pressure dissipation rate was the fastest at this threshold. The cohesion, internal friction angle and sediment strength are larger at the same time.4)The cohesive sediment affected by salinity in the positive and negative potential balance, so sedimentary environment can influence consolidation process. The main reason is the psephicity of newly formed clay particles, as well as the arrangement between the particles.The main innovations in this dissertation include:l)The complex salinity field partition of the river estuary region is built. The relationship between the feature of the sediment in the typical area and salinity is revealed. So does the threshold of salinity.2)The consolidation process under different salinity sedimentary environment is discussed. And the relationship between physical and mechanical properties of the sediment and the salinity of sedimentary environment is established.