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Purpose: Compression studies can provide insights into evaluating the engineering potential and environmental impact of clay. The objective of this study was to quantitatively investigate the bound water characteristics and microstructure evolution during uniaxial compression of mucky silty clay and to explore the effects of structure, loading, and time on the secondary compression. Materials and methods: An integrated approach was developed to investigate the macro compression characteristics of Qingdao clay and the evolution of pore water and microstructure during compression using uniaxial confined compression tests involving multi-stage and separate loading, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Results and discussion: The secondary compression coefficient (Cα) increases with the vertical stress ( σ v ′ ) to a peak and slowly decreases above the yield stress ( σ vy ′ ). The value of Cα decreases with time. The expulsion of free water occurs for σ v ′ < σ vy ′ corresponding to a change in the trellis pores, whereas the extraction of weakly bound water begins when σ v ′ > σ vy ′ , accompanied by the increased fineness and regularity of intergranular pores. The microstructure changes from a loose skeleton-flocculate to a compact agglomerate structure as the vertical stress increases. The apparent area proportions increase with the vertical stress for pores with equivalent diameters (d) < 1 μm, d = 1 ~ 2 μm, and d = 2 ~ 5 μm; however, both the number and apparent area proportion decrease for the trellis pores with d = 5 ~ 10 μm. A four-tiered, three-stage conceptual microstructure model is established to elucidate the compression mechanism. Conclusions: Structural collapse and the expulsion of weakly bound water produce a peak in Cα. The finiteness of particle dislocation and the change of bound water film lead to a decrease in Cα with the vertical stress and time. [ABSTRACT FROM AUTHOR]