Transformation Of Granular Composition And Microstructure Of Silt Due To Cyclic Loading In Yellow R. Estuary, China

The dissertation is sponsored by the project of National Nature Science Foundation Project Formation and Failure of Hard Crust on the Subaqueous Delta of Yellow River(Contract No: 141720888), and its aim is to study the transformation process of granularity composition and microstructure of silt due to cyclic loading. It is found that hard crust developed generally on the tidal flat of Yellow River estuary and the growth grade adapt to the hydrodynamic action, but the mechanism of this change process is unknown. What is likely to change about the composition and microstructure of the seabed silt under cyclic load like wave load, is related nearly to the seabed's geology environment and the gestation of the geology disaster. In this dissertation, the variation of sediment's composition and microstructure is analyzed on the base of field and indoor test and the integration with the fractional geology theory . First of all, the formal field survey data is generalized and the variation of sediment character due to different hydrodynamic action is discussed; on this base, the later formation cause of the sediment's layer and sullage evolve is studied . The pivot of the dissertation is the field physical simulation test, First ,the typical area was chosen on the tidal flat of Yellow River estuary where hard crust develop, simulatmg wave load test with a light compactor was carried out to study the repeat liquefaction and change law of crust layer within one meter through the monitoring of pore water pressure and in-situ soil strength measure; we took the undisturbed columniation sample of 1 meter before and after cyclic vibratin,the microstructure has been observed with SEM and the transformation characteristics of the granularity have been contrasted every 10 cm; on this base ,we discuss the relativity between dynamic response and microstructure, and also discuss the cause formation of hard crust from microstructure angle. After the plentiful field test, the sediment's evolve is studied through the physical simulation in laboratory. At last, we discuss the principium mechanism of transformation of silt's granularity and microstructure...