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The compressibility and microstructural changes of four types of reconstituted clays, Tianjin, Shanghai, kaolin, and montmorillonite clays, were studied to investigate the effects of mineral composition and clay content on the compressibility and microstructure evolution of clays during one-dimensional (1D) compression. The scanning electron microscopy test results indicated that the clays were characterized by an aggregated structure with inter- and intraaggregate pores. A preferential orientation of the particles toward the horizontal plane was induced during the 1D compression. The mercury intrusion porosimetry test results showed that the cumulative pore volume clearly decreased and that the volume and size of the widely distributed interaggregate pores decreased with the increase of the vertical effective stress. For montmorillonite clay, particle reorientation was obvious due to the more loosened microstructure, and the volume of mesopores was much larger compared to other clays, which resulted in the largest compressibility. For kaolin clay, a distinct preferential orientation of the particles toward the horizontal plane was induced due to the more planar microstructure even under the lower vertical effective stress, and the decrease of the pore volume mainly arose from micropores compared to mesopores in other clays. For the tested Tianjin and Shanghai clays, the main minerals were the same, but the compressibility of Tianjin clay was larger. It seems that the higher the clay content, the larger the particle reorientation and the cumulative pore volume, the higher the compressibility. [ABSTRACT FROM AUTHOR]