Abstract: Based on the geotechnical investigation results of a super large Zhanjiang steel factory site, and on the basis of the large amount of data obtained, this paper analyzes the horizontal and vertical variabilities of the structural clay of Zhanjiang Formation. Two typical geomorphic units are selected and analyzed for the variation of the physical and mechanical indexes of the clay of Zhanjiang Formation. The results indicate that: (1) the top surface of the clay layer in Zhanjiang Formation is generally distributed in a wavy shape in space, with the irregular spatial distribution and significant differences. (2) From the top to the bottom, the number of standard penetration tests (SPT) increases with depth in Zhanjiang Formation clay, following a linear variation pattern. (3) The particle size distribution and material source of Zhanjiang Formation clay with different embedment depths and plane positions are relatively stable, with the high liquid limits and the high plasticity. There are significant differences in other physical and mechanical indicators, but there is a linear variation pattern with the depth. These investigations provide a basis for the selection of geotechnical design parameters, and adds value to the design and construction projects.

Key words: Zhanjiang Formation Clay, Plane Variability, Vertical Variability, Physical and Mechanical Indexes, Regression Analysis