Dynamic Behavior And Mechanism Analysis Of Structural Clay Under Traffic Loading

With the rapid development of city transportation in China, geotechnical engineering problem caused by traffic loading has been noticed by an increasing number of people. A great many researches on saturated clay's strength and deformation behavior have been done by many researchers, however, these researches keep more eyes on macro-mechanics, but keep less eyes on micro-mechanics which is the main reason for structural clay's macro dynamic reaction. Therefore, in order to reflect clay's real dynamic behavior under complex stress condition (initial stress+cyclic loading), on the basis of profound and fine experiments of mechanic behavior, paying more attention to the research on clay's micro fabric and physical mechanism and on clay's volume-contraction in unloading and reversible dilatancy under cyclic loading, discovering that the relationship between clay's micro fabric changes and its macro mechanic response and that physical foundation among clay's dilatancy, anisotropy and structure, developing dynamic constitutive model with having a right physical concept, a simple mathematic representation and a easily measured parameter. On the basis of the present research, emphasizing on the research on experiment in structural clay's dynamic behavior under traffic loading, at the same time, giving a profound analysis from micro angle, the main work of this thesis is as followed:1. By conducting indoor physical and mechanic experiments, statics property about typical silty clay from Tianjin Tangku area has been analysed, putting more emphasis on structural effect of such soil, its structural strength value has been obtained according to a mathematic model.2. By taking advantage of half sine wave to simulate traffic loading, based on cyclic triaxial test, structural clay's dynamic strength property has been studied, obtaining such structural clay's critical dynamic stress ratio and threshold dynamic stress ratio, getting its dynamic strength index and its variation regularity, at the same time, put forward a kind of pore pressure model reflecting such clay's dynamic characteristic by using experiment results.3. By making use of cyclic triaxial test reflecting different stress path to simulate structural clay's response under traffic loading, the research which reflects structural clay's dynamic stress-strain relationship under different consolidation modes, different frequencies of vibration and different waveforms of vibration has been conducted, discovering that structural clay's dynamic stress-strain relationship under traffic loading can be described as hyperbola, obtaining that such clay's maximum dynamic Young's modulus E_{max d} and maximum dynamic shear modulus G_maxd.4. According to the results of research above, by using quantification analysis of micro structure to show micro mechanism caused by macro mechanic behavior, taking advantage of mercury intrusion porosimetry, comparing the change of pore size distribution during the loss of structure strength of the structural clay, it is analysed that structural clay's micro mechanism of dynamic behavior under traffic loading.