Study On Sequence Division Of Quaternary Soil Layer In Zhenjiang Based On Uncertainty Theory

Soil is a natural or artificial product formed in a specific sedimentary environment,and its physical and mechanical properties are related to deposition time,physical and chemical action and other factors.The physical and mechanical indexes of soil,such as water content,void ratio,liquid index and compression modulus,are generally uncertain,which directly shows that the dispersion degree of index parameters is too large,which leads to the decrease of the reliability of geotechnical parameters,and then affects the application of reliability theory in geotechnical engineering design.The values of soil parameters in a region tend to be relatively stable.It is of positive practical significance to strengthen the statistical analysis of regional soil parameters and establish regional standard strata for guiding engineering construction.In order to summarize the distribution characteristics of foundation soil under different stratigraphic age and sedimentary environment conditions in Zhenjiang area,this paper divides the geomorphic units of Zhenjiang area into mountain,hill,hilly,valley and beach according to the provisions of microgeomorphic morphology,genesis,stratigraphic characteristics and national and local norms.The distribution characteristics of foundation soil property parameters under different stratigraphic age and sedimentary environment conditions in Zhenjiang area are summarized.In order to obtain the linear correlation between physical and mechanical parameters of soil layer under different strata ages and different sedimentary environment conditions in Zhenjiang area,based on the classical mathematical statistics theory,this paper makes statistical analysis according to different geomorphic units such as hillock,beach and valley,solves the correlation coefficient between physical and mechanical parameters of soil and evaluates the correlation degree.It is concluded that the linear correlation between the physical and mechanical parameters of Q3 formation is significantly higher than that of Q4 formation,and that the uniformity of soil material composition and the variability of soil structure are the main factors affecting the correlation between different parameters.In order to grasp the random characteristics of the foundation soil in Zhenjiang area,based on the random field theory and the static cone penetration test data of different strata age,sedimentary environment and geotechnical types in Zhenjiang area,the representative values and variation coefficients of the vertical and horizontal correlation distances of different soil layers are calculated,and the calculation results of different methods such as the recursive space method and the new method are compared.The results show that the spatial variability and soil layer uniformity are the main factors affecting the correlation distance.Based on the application of geotechnical classification,statistical principle of geotechnical parameters and random field theory in the statistical process of geotechnical parameters,the soil layer is divided according to specific engineering cases,and it is pointed out that the subdivision of soil layer is helpful to further reduce the variation coefficient of soil parameters.Finally,the Zhenjiang area is divided into four main engineering geological layers and 17 sub layers,the characteristics of the related standard strata are described systematically.