RESERCH ON ENGINEERING GEOLOGICAL CHARACTERISTICS OF GREY-BLACK CLAY BASED ON INTEGRATED STRATIGRAPHY

Precise stratigraphic division is of great importance for the statistical, physical, and mechanical indexes of strata in geotechnical engineering. It is considered that any kind of stratigraphic method is limited, and because integrated stratigraphy can provide an effective approach for the division and correlation of strata, using integrated stratigraphy theory is becoming increasingly popular. In this study, combined with the borehole information of the urban geological survey in Jining city, the sequence division scheme of the grey-black clay strata is redefined through multiple stratigraphic division and correlation for lithostratigraphy, sedimentology, biostratigraphy, and chronostratigraphy study. Based on in-situ and laboratory geotechnical tests of the 18 project sites in Jining, the engineering geological characteristics of the grey-black clay are systematically investigated. Generally, the clay has the characteristics of a big void ratio, high compressibility, low shear strength, and low index of in-situ test. More significantly from a stratigraphic division perspective, the Heituhu formation is a kind of normal clay, while the Baiyunhu formation belongs to the high liquid limit muddy clay, which is a special kind of soil. It is necessary to separate the special soil from normal soil in engineering. According to the current research situation in the field of integrated stratigraphy and geotechnical engineering, a new research direction that should be well investigated in the future was proposed, that is, researchers should not only use geological theory to explain strata problems in geotechnical engineering but also use geotechnical engineering data to find new strata problems.