Large scale land reclamation and the effects on hydro-mechanical behavior in loess and loess-derived fill

To discover the complex hydro-mechanical evolution on Loess Plateau that accompany large-scale land reclamation project, we tracked changes of moisture, matric suction, anisotropic displacements and stresses in geological interfaces of natural loess and deep man-made fill during a comprehensive process of construction and the subsequent three years rest period. Results indicate that vertical stress increases during emplacement of thick fill, while the lateral earth pressure first increases and then gradually decreases with elapsed time. There was a non-linear increase in lateral earth pressure with depth of infill during construction. Whereas lateral earth pressure decreased with depth in lengthy rest period. The fill vertically compressesed and laterally extended during construction, while the geological interface of fill and loess laterally rebounded during construction pause. The primary vertical displacement occurred at the contact zone between the original loess slope and fill. The lateral earth pressure coefficient of infill is influenced by lateral compression and extension of contact zone during land reclamation process. It mirrors the observation that variations in lateral earth pressure with depth are dependent on deformation of natural slope materials. Interestingly, vertical stress and lateral earth pressure periodically fluctuated during rest period, correlating to creeping and shrinkage in loess influenced by moisture content change under different environmental relative humidity. The volumetric moisture contents in fill and contact zone significantly increased during construction. The moisture content of contact zone is 10% higher than the overlying higher density fill after construction, which is attribute to the process of matric suction equilibrium. Considering a constant moisture content, the ratio of historical mean principal stress to deviatoric stress in fill and interface are under the principal stress failure line during construction. However, water diffusion potentially threats the stability of this man-made geological structure.