Relationship between the Microscopic Pore Distribution and Permeability Characteristics of Soft Clay in Multi-Phase Reclamation Lands in Chongming East Shoal

Nowadays, land reclamation by dredger fill has become one of the effective ways to solve the increasing land demand in coastal areas. However, the artificial dredger fill could not only produce large deformation after it was deposited, but also further the permeability and consolidation of the underlying soft clay (USC) layer, resulting in long-term and slow ground deformation. Nevertheless, the permeability characteristics of USC attracted insufficient attention, especially in multi-phase reclamation lands. Furthermore, the microscopic mechanism analysis of permeability characteristics still needs to be enriched. Hence, it is necessary to clarify the relationship of permeability characteristics and microscopic pore distribution so that appropriate guides could be provided to resist the potential deformation of the soil foundation. This paper takes Chongming East Shoal (CES) as the study area, the variable head permeability test is used to study the permeability characteristics of soil samples, and the mercury injection test (MIP) and scanning electron microscope (SEM) image are applied to analyze the corresponding microscopic mechanisms. The fractal theory was used to analyze the complexity and connectivity of soil pores, and a new empirical parameter fractal dimension contribution factor is proposed. Results show that a higher permeability efficiency benefited from the increase of mesopores content and the decrease of small pores content, lower fractal dimension, and stronger agglomeration of clay particles. Furthermore, statistical regression analysis presents that permeability coefficient is significantly positively correlated with the average and median pore size, and significantly negatively correlated with the fractal dimension. The study could provide a reference for the safe use of foundation soil in reclamation areas