DEM-FDM coupled simulation of cone penetration tests in a virtual calibration chamber with sand

The cone penetration test, considered one of the most crucial in-situ testing methods in geotechnical engineering, is unable to directly measure soil parameters. Generally, the empirical relationship between penetration resistance and soil parameters is established through laboratory calibration chamber tests or numerical simulations. In this research, a coupled numerical approach employing discrete element (DEM) and finite difference method (FDM) is employed to simulate the entire cone penetration test process within a calibration chamber and unveil the mechanisms that influence penetration resistance. First, the microscopic parameters of the sand are calibrated based on its macroscopic behaviors. Additionally, the impacts of calibration chamber size, sand density, and confining stress on penetration resistance are thoroughly analyzed. Finally, a relationship is established between the normalized penetration resistance Q and the peak internal friction angle φpeak. The findings indicate that the size effect in the simulation becomes negligible when the continuous-discrete model size ratio Rdf reaches 0.67 and the normalized radial length Rd of the calibration chamber is set at 20. Furthermore, the simulated penetration resistance closely matches the results obtained by cavity expansion methods, confirming the reliability of the numerical simulation. An exponential relationship is observed between Q and φpeak, which closely aligns with in-situ test results. This further validates the accuracy of the coupled simulation method. These outcomes offer valuable insights for establishing empirical relationships between cone penetration resistance in sand and soil parameters in geotechnical engineering.