Determination of Mechanical Properties of Soils Based on CPTU Data

The study aimed to interpret the results of cone penetration tests with pore pressure measurement (CPTU). Tests were performed on a section of the designed road about 200 m long. The subsoil under consideration was characterized by organic soils deposited to a depth of approximately 8 m. Due to the problematic soil and water conditions, improvement with geosynthetic encased columns (GEC) was performed. According to the Recommendations for Design and Analysis of Earth Structures using Geosynthetic Reinforcements – EBGEO, the constrained modulus E_oed and effective friction angle φ’ of soil below the GEC column base should be higher than 5 MPa (E_oed > 5 MPa) and 30° (φ’ > 30°), respectively. In this study, the E_oed and φ’ parameters were determined based on CPTU tests conducted in 12 locations. Analysis of the CPTU data showed that the constrained modulus and effective friction angle of the soil deposited below the GEC column base did not meet EBGEO requirements in most locations. It was also concluded that the minimum value of the constrained modulus required by EBGEO is too low compared with the requested value of the effective friction angle.