Classification of Miocene deposits using CPT data

Antonia Makra and Hobi Kim have co-authored a paper titled: “Classification of Miocene deposits using CPT data” which has been published in the Proceedings of the 5th International Symposium on Cone Penetration Testing (CPT '22) in Bologna, Italy.

This paper discusses how classification charts used for soil classification based on CPT

data, linking the type of soil behaviour to the measured tip resistance, sleeve friction and pore water pressure, have been successful in interpreting soil behaviour in young, saturated, uncemented soil deposits, but often diverge from observations in samples in older deposits. The geotechnical investigation conducted for the 1915 Çanakkale bridge included 20 offshore boreholes with 18 adjacent CPT soundings conducted downhole that penetrated several meters into Miocene-age sediments. This paper investigates those data sets and proposes a modified chart for the classification of the Miocene deposits accounting for their microstructure. The proposed modification is useful for classifying Miocene deposits in similar geological settings through the performance of CPTs.

You can find this paper online here!

GR8 GEO participated in LEAP 2020 research program

GR8 GEO participated in 2020 Liquefaction Experiments and Analysis Projects (LEAP-2020) research program by performing Type-B (blind) numerical simulations for seven (7) of the centrifuge tests using the Ta-Ger constitutive model implemented in FLAC to predict the seismic response of a sheet-pile retaining structure supporting liquefiable soils. The present paper presents the Type-B predictions in comparison with the experimental results. Calibration of the Ta-Ger model based on available laboratory DSS data focused on capturing the liquefaction resistance for a large range of cycles, the post-liquefaction rate of shear-strain accumulation, the overburden effects and realistic shear stress-strain responses. A single numerical model was built in FLAC in prototype scale in accordance with the design geometry of the LEAP 2020 testing program. Numerical analyses were performed varying only the input seismic motion applied to the model. Numerical analyses captured the primary mechanisms of the system response such as liquefaction in the free-field, negative pore pressure behind the wall accompanied by the outward rotation of the wall.

Our team had the closest predictions for the largest number of centrifuge tests compared to the other program participants (a total of 10 teams from around the world participated in the numerical modeling exercise using more than 6 different constitutive models). A paper in the LEAP 2020 Workshop Proceedings will soon be published. Stay tuned!

OWT bucket foundations in sand: 3D coupled effective stress analysis with Ta-Ger model

Panagiota Tasiopoulou, Yannis Chaloulos, Nikos Gerolymos, Amalia Giannakou and Jacob Chacko have co-authored a paper titled: “Cyclic Lateral Response of OWT Bucket Foundations in Sand: 3D Coupled Effective Stress Analysis with Ta-Ger Model” which has been published in Soils and Foundations. In this paper, the multiaxial sand constitutive model Ta-Ger (Tasiopoulou and Gerolymos, 2016a,2016b) implemented in the finite deference code FLAC3D is employed in the analysis of the lateral response of bucket (skirted) foundations subjected to wind/wave loading. The model has been adjusted to reproduce the cyclic response of sand for undrained, fully drained and the intermediate conditions, using a unique set of calibration parameters. Numerical validation is conducted against centrifuge test including a bucket foundation in dry sand, by building a 3D numerical model.

In order to gain qualitative insights into the effect of drainage conditions, the same problem used for validation was analyzed under saturated conditions and a range of soil permeabilities. It was shown that when flow is allowed the response up to a cycle threshold resembles that of fully drained conditions. Increasing the permeability delays the occurrence of liquefaction and the associated development of large deformations. You can find it online here!