This paper proposes a numerical framework to simulate in-situ free fall cone penetration tests conducted on soft and sensitive marine clay. First, the free fall cone penetration tests are carried out at an offshore site in the northern part of the Gulf of Finland, Baltic Sea. The numerical simulation employs the Generalized Interpolation Material Point Method to replicate the process of indentation of the cone penetrometer into the clay. The clay is modelled using an advanced constitutive model that considers the effect of strain rate and strain softening associated with the dynamic penetration process. The simulation uses a friction contact model to represent the interface between the cone penetrometer and the clay. The numerical simulation accurately replicates the penetration process associated with the tests. @en

This paper presents a series of laboratory free‐fall cone penetrometer (FFCP) tests conducted on marine clay samples collected from the Gulf of Finland in the Baltic Sea. Subsequently, these tests are replicated numerically with the generalized interpolation material point method (GIMP) simulations. First, the paper gives laboratory‐scale FFCP experiment results used for the validation of the numerical framework. In these experiments, a small‐scale model of a FFCP was dropped from various heights into a natural marine clay soil sample and recorded using a high‐speed camera. The tests were supplemented with a laboratory test program to determine the geotechnical properties of the clay used in the experiments. Following image processing, the tests provided data for numerical simulations: displacement, velocity, acceleration, and reaction force curves associated with the FFCP during the penetration process. The GIMP simulations shown in the paper replicate the process of penetration of the FFCP into the marine clay. The simulations used a strain‐rate dependent Tresca constitutive model, extended with strain softening that replicates the reduction of the undrained shear strength due to destructuration, an important feature of the material. The numerical simulations replicate the experiments well. The study examines the effect of cone penetrometer roughness, impact velocity, mesh density, strain rate, and strain softening on the cone penetrometer penetration process. The simulation results indicate that the presented framework can replicate the dynamic penetration process on soft and sensitive clay very well.@en

In situ free-fall cone penetrometers (FF-CPTs) allow for rapid investigations of undrained shear strength of soft shallow water deposits. Often samples are also studied in geotechnical laboratory by fall cone tests. This study presents in situ FF-CPT and laboratory fall cone testing results of an offshore site in the northern part of the Gulf of Finland, Baltic Sea. Site investigations included seismoacoustic surveys and sediment coring. Based on seismoacoustic reflection profiles and long sediment cores, the local deposits were classified and divided into glaciolacustrine, post-glacial lacustrine and brackish-water stratigraphic units. FFCPT measurements provided in situ undrained shear strength and dynamic cone resistance of the seabed geological units. Laboratory fall cone tests were performed on the vertical core samples at every 0.5m. Comparisons were established between undrained shear strength from FF-CPT tests and from fall cone tests.@en

The paper presents experimental results of investigations of offshore deposits from the Gulf of Finland in the Baltic Sea. Firstly, it briefly reviews the sedimentary history of the studied site. Then, it presents results from marine geological investigations, including seismoacoustic reflection sub-bottom profiles and long sediment cores collected by piston coring. Finally, the paper presents the physical and mechanical properties of the intact soil samples through geotechnical laboratory tests. The data show the distribution of water content, bulk density, undrained shear strength, sensitivity, and organic content of the samples at various depths up to approximately 4 meters. The undrained shear strengths, obtained by fall cone tests, are scattered and the variations are ±35% for the studied specimens. A quantitative correlation between geotechnical data and local sedimentary units and depositional history was not possible in this study. Further efforts are needed to reduce the uncertainties and measurement errors in determining the undrained shear strengths in geotechnical laboratory.@en