Correlative Analysis Between Cone Tip Resistance Of CPT And Soil Strength

The static cone penetration test (CPT) because of being provided with rapid, accurate and reproducible advantages, often used in surveying stratigraphic information. In soft soil areas using CPT to determine the undrained shear strength of soil is considered viable and accepted by many scholars and research institutions at home and abroad. Based on plenty of test, The experimental equations are developed to determine the undrained shear strength of soil, which are applicable in different region.These experimental formulae are not very universal, and their exact level are unknown. In order to deeply understand the penetration mechanism of CPT, This paper focuses on the relationship between cone tip resistance and soil strength to start research work. Specific content as follows:First, give a simple narrative on basic equipment, basic principles and mechanisms of static cone penetration, and a detailed overview of theoretical research, laboratory simulation experimental study and numerical simulation analysis. However, the theoretical solution made various assumptions for soil behavior, such as surface roughness, smoothness, etc. the result that estimated by different assumptions have bigger difference. Thus using the empirical method of statistical analysis to determine the undrained shear strength of soft soil is a more practical approach.Then, the field data collected from Shanghai and Wuhan are analyzed by using regression and correlation method, some static sounding data and laboratory experimental data (19projects in Shanghai and33projects in Wuhan, which included632sets of data). Regression analysis were compared to their penetration resistance Ps and shear strength Su correlation for clay and silty clay, and proposed the determine way of shear strength index Su shallow foundations in the area on this basis. At the same time, through analysis, get the probabilistic characteristics of the bearing capacity factor Nc in both regions in the clay, which include the mean, variance and distribution scheme. Data analysis result indicated that Nc in Wuhan is higher than in Shanghai areaNext, the ABAQUS finite element model with using the Mohr-coulomb yield criterion is established to simulation analysis relationship between cone resistance and soil strength in static sounding penetration process, the change regularity of displacement and stress of soil after the static sounding probe penetration are calculated and analyzed. The calculating results show that cone tip resistance and the bearing capacity factor have the varying degree increases with the cohesive force, elasticity modulus and friction angle. These conclusions have explanations for why Nc in Wuhan is higher than in Shanghai. And the formula which between soil physical parameters and cone tip resistance in finite element calculation are established, which are compared with the empirical formula.Finally, through the actual engineering case analysis in Wuhan, the mean of finite element analysis and regression analysis based on the measured data are analyzed and compared to discover the differences. The results show that the calculated results accord with the experimental values. Although the calculation results by FEM have relatively large difference to the experimental results, they reflect the strength character of different depth of soft soil in whole.