Studies On Theory Of One-dimensional Consolidation For Layered Structured Aquitard Soils In Leakage System

In China’s coastal areas and areas along Yangtze, thick soft clays are deeply and widely distributed. When pumping groundwater in these regions, the phenomenon of hydraulic connection occurs for the reason of existence of hydraulic gradient imbalance between aquitard clays and aquifer, which finally causes land subsidence. As for the aquitard soils, they are generally structured due to sedimentary force, depositional environment and particle cementation during formation history. Thus, the consolidation for structured aquitard soils will perform different behaviors with those of little consideration of structural characteristics. Also, the divergence cannot be ignored when precisely predicting the value of land subsidence. In this thesis, the theory for one dimensional consolidation of layered structured aquitard soils in leakage system and the relevant consolidation behaviors are studied by using analytical method. The main original works are as follows:(1) Based on one dimensional consolidation theory of double-layered soils, the governing equation expressed by water head for single-layered structured soils are established by using the simplified model of kv-σ’and mv-σ’which represent the variation of permeability and compressibility respectively for structured behaviors. Then, the analytical expressions of water head, pore pressure, settlement and degree of consolidation are deduced in the case of general time-dependent, instantaneous and linear decline of confined aquifer water level respectively. The solutions obtained in the non-structured form are perfectly consistence with previous ones, which proved to be reasonable. By comparing different examples, the effects of structured behaviors on consolidation are analyzed.(2) General solutions are derived for one dimensional consolidation of double-layered structured soils with groundwater withdrawal in the confined and unconfined aquifer respectively. By using calculating examples, a comparative analysis has been made to elaborate the essence of the relationship between consolidation of structured soils induced by groundwater drawdown and that of ones induced by loading. The effects of the relative values of structural yield stress of both layers on the consolidation rate and settlement are analyzed.(3) Analytical solutions are obtained for one dimensional consolidation of multi-layered structured soils with groundwater drawdown in the confined aquifer. The influences of structured behaviors on water head, pore pressure, settlement and sedimentation rate are analyzed, and those of varied values of structural yield stress of intercalary soil on consolidation rate and settlement are investigated.