GEOLAB and Industry

PEBSTER Project

Project Scope

 Reinforced piled embankments make infrastructure projects on soft soils feasible. Current design practice assumes a perfectly rigid pile behaviour and uses analytical design methods that were developed for geosynthetic reinforcement. However, piles usually show some settlement. Welded steel mesh reinforcement is applied sometimes instead of geosynthetics, especially for high embankments. The PEBSTER test program addresses knowledge gaps in the load transfer mechanism of steel-reinforced piled embankments, and the difference between rigid and flexible piles. Therefore, model tests at two scales were planned: small-scale model tests at Deltares and large-scale model tests at TU Darmstadt. The research program was developed in close cooperation with the research group led by Keller.

The small-scale test set-up consisted of an embankment founded on four piles with a basal steel reinforcement. The consolidation of the soft soil between the piles was simulated by draining a saturated foam cushion. Surcharge loads up to 100 kPa were applied, to match the prototype stress in an embankment with a height of about 5 m.
In the four small–scale tests, the following variations were made:

  • Steel reinforcement or no steel reinforcement;
  • Rigid piles or piles on springs, comparing the theoretical model with a more realistic behaviour;
  • Stepwise or continuous consolidation, emulating different construction sequences.

Force and pressure cells were used to capture the load distribution. Steel and soil strains as well as 3D soil displacements were measured using innovative Distributed Fibre Optic Sensing (DFOS) technology.

In a follow-up, the large-scale test at TU Darmstadt will serve to verify and translate the findings to an almost true scale.

Innovative Aspects and Main Results

This research project introduces innovative approaches to enhancing the resilience and sustainability of piled embankments through the application of welded steel mesh as basal reinforcement, a departure from the traditional use of geosynthetic geogrids. The project aims to explore the load transfer mechanisms facilitated by the steel mesh, and to explore, if existing analytical models for geosynthetic geogrids can be applied for steel meshes as well. Additionally, it seeks to understand the impact of pile flexibility and soft soil consolidation on these mechanisms. Employing cutting-edge distributed fiber optic sensing (DFOS) technology across small-scale and large-scale tests, the project will offer comprehensive insights into the fill-reinforcement-piles-soil interaction, enabling a significant leap forward in the design and construction of more resilient piled embankments. These innovations have been made possible through the joint efforts of the global building company Keller, the construction monitoring firm SHM System (Poland), the Dutch knowledge institute for water and the subsurface Deltares, and the Technical University of Darmstadt (Germany), within the framework of GEOLAB.

Publications from PEBSTER: 

  • M. Schneider, M. Hel, P. Pandrea, B. Wittekoek, S.J.M. van Eekelen,M. Topolnicki, K. Makowska, R. Sieńko, & H. Zachert (2024). High-density spatial measurements on a 3D large-scale model of a basal steel-reinforced piled embankment. Proceedings of the 5th European Conference on Physical Modelling in Geotechnics, 2-4 October 2024, Delft, The Netherlands.
  • S.J.M. van Eekelen, M. Schneider, M. Hell, K. Makowska, K. Zdanowicz, B. Wittekoek, P. Pandrea, R. Sieńko, P. Schauber, M. Topolnicki, H. Zachert (2024). Distributed Fibre Optic Sensing (DFOS) in 3D small-scale tests on steel-reinforced piled embankments. Proceedings of the 5th European Conference on Physical Modelling in Geotechnics, 2-4 October 2024, Delft, The Netherlands.
  • M Schneider, M. Hell, B. Wittekoek, S. van Eekelen, P. Schauber, P. Pandrea, M. Topolnicki, K. Makowska, & H. Zachert. Untersuchungen zum Tragverhalten von Piled Embankments im
  • Großversuch (Investigations into the load-bearing behaviour of piled embankments in large-scale test). Darmstädter Geotechnik-Kolloqium, 7 March 2024, Darmstadt, Germany.
Facilities Details
Name TU Darmstadt Pile Test Pit / Deltares Geo Model Hall
Owner TU Darmstadt / Deltares
Location Darmstadt, Germany / Deltares, Netherlands
Website Click Here To Visit Darmstadt Website
Website Click Here To Visit Deltares Website
Head of facilities Hauke Zachert / Suzanne Van Eekelen
Contact Hauke Zachert (hauke.zachert@tu-darmstadt.de) / Suzanne Van Eekelen (hauke.zachert@tu-darmstadt.de)

JELLYFISH Project

Project Scope

The project aims to advancement of knowledge on the geotechnical characterization of different soil deposits (soft clays, quick clays, intermediate soils, sands) by use of innovative in-situ testing procedures. The adopted experimental methodology is based on the use of the Medusa DMT, the ‘smart’ fully automated version of the flat dilatometer (DMT). In the Transnational Access period an extensive in-situ testing campaign with the Medusa SDMT (seismic equipment configuration) was carried out at four benchmark test sites in Norway, part of the Geo-Test Sites (NGTS) research infrastructure managed by NGI. Medusa (S)DMT tests were carried out using both ‘standard’ and innovative ‘non-standard’ testing procedures.

Innovative Aspects & Main Results

Studio Prof. Marchetti S.R.L – Italy, a SME manufacturing the Marchetti Flat Dilatometer (DMT), tested their innovative Medusa DMT in NGI’s test sites in collaboration with University of L’Aquila, University of Chieti-Pescara and NGI. The Medusa DMT is a newly developed self-contained probe, cable of operating autonomously using a standard blade without the pneumatic cable, the control unit and the gas tank required in the traditional pneumatic DMT. This innovative ground investigation equipment were tested at NGI’s soft clay, quick clay, silt and sand test sites through the support from GEOLAB’s Transnational Access project – JELLYFISh. GEOLAB contributes to bringing the innovation to practice at TRL 8-9 in this project. The outcomes of JELLYFISh contributes to advance the development of innovative soil investigation techniques which is of instrumental importance to increase design safety and resilience of European Infrastructure.

Publications from JELLYFISH: 

  • Monaco, P., Chiaradonna, A., Marchetti, D., Amoroso, S., L’Heureux, J-S. and Le, T.M.H. (2023). “Recent developments in soil investigation by Medusa SDMT.” Geotechnical Engineering in the Digital and Technological Innovation Era, Proc. 8th Italian Conference of Researchers in Geotechnical Engineering CNRIG 2023, Palermo, Italy, 5-7 July 2023, Ferrari A., Rosone M., Ziccarelli M. and Gottardi G. (eds), 234-241, Springer Series in Geomechanics and Geoengineering, https://doi.org/10.1007/978-3-031-34761-0_29
  • Monaco, P., Chiaradonna, A., Marchetti, D., Amoroso, S., L’Heureux, J-S. and Le, T.M.H. (2023). “Medusa SDMT testing at the Onsøy Geo-Test Site, Norway.” Proc. 8th International Symposium on Deformation Characteristics of Geomaterials IS-Porto 2023, Porto, Portugal, 3-6 September 2023, Viana da Fonseca A. and Ferreira C. (eds), available at https://www.issmge.org/publications/online-library
  • Monaco, P., Chiaradonna, A., Marchetti, D., Amoroso, S., L’Heureux, J-S. and Le, T.M.H. (2023). “Potential of the Medusa DMT for offshore geotechnical investigation.” Innovative Geotechnologies for Energy Transition, Proc. 9th International SUT Offshore Site Investigation and Geotechnics Conference OSIG 2023, London, UK, 12-14 September 2023, 1889-1896.
  • Conference papers in preparation to be published in 2024 (current status & deadlines)
  • Monaco, P., Amoroso, S., Chiaradonna, A., Marchetti, D., Le, T.M.H. and L’Heureux, J-S. (2024). “Characterization of intermediate soils by innovative in-situ testing procedures using Medusa DMT.” XVIII European Conference on Soil Mechanics and Geotechnical Engineering ECSMGE 2024, Lisbon, Portugal, 26-30 August 2024. Paper submitted 30 November 2023, under review.
  • Monaco, P., Chiaradonna, A., Marchetti, D., Amoroso, S., L’Heureux, J-S. and Le, T.M.H. (2024). “The JELLYFISh Project: Medusa SDMT testing at NGTS Geo-Test sites, Norway.” 7th International Conference on Geotechnical and Geophysical Site Characterization ISC’7, Barcelona, Spain, 18-21 June 2024. Paper due 15 February 2024, under preparation.
  • Journal
  • Monaco, P., Chiaradonna, A., Marchetti, D., Amoroso, S., Le, T.M.H. and L’Heureux, J-S. 2024 «Soil characterization using Medusa SDMT at NGTS Geo-Test sites, Norway” – Geotechnique (under preparation)

 

Facility Details
Name Geotest Sites
Short Name NGTS
Owner Norwegian Geotechnical Institute (NGI)
Location Oslo / Norway
Website Click Here to Visit Site
Contact Thi Minh Hue Le
Head of facility Jean-Sebastien L'Heureux

CLARIFIER Project

Project Scope

To answer the research questions about the feasibility of modelling peat in a geotechnical centrifuge and about failure mechanisms of light weight embankments, two types of tests were conducted:

  • Modelling-of-models tests at 30 g, 50 g, and 70 g. Testing models scaled from the same prototype dimension to different sizes/g-levels helps to understand whether the established scaling laws hold for a specific test material or setup. In the current tests, the peat was loaded with a load plate. The height of the peat layer (7.5 m at prototype scale) and the width of the load plate (5 m at prototype scale) were scaled to the different g-levels to achieve comparable models.
  • Embankment tests at 50 g. In these tests, an embankment was constructed on the peat surface. The height of the embankment was chosen following the experience from four trial embankments that were constructed in Norway in 1963-64. In these, the settlement of the embankment under self-weight resulted in the saw dust layer being fully saturated and the sand layer staying mostly dry. Traffic loads were simulated using a double t-shaped loading device.

Three tests were conducted using the same test setup to examine the variability of results that could result from differences in the peat samples. An additional test was conducted introducing a geotextile underneath the embankment. All tests were performed using peat samples from a test site in Trondheim, Norway. The samples were cut in place, transported in custom made boxes, and arrived at the testing facilities without any visual change. As such, they were here considered to be undisturbed.

In all tests, mini-CPTs were conducted to provide strength profiles and gain additional insight into potentials of centrifuge testing of peat.

Innovative Aspects & Main Results

Model testing in geotechnical centrifuges has proven an effective tool to study deformation and failure mechanisms in soil materials. However, available research about modelling peat in a centrifuge is limited and there are some concerns regarding the influence of fibers at model vs. prototype scale. Few experiments are known to the user group where intact samples of natural fibrous peat samples were tested. Investigating the potential of and possible limitations to studying peat in the centrifuge, CLARIFIER contributes to a recent body of knowledge that will facilitate research for sustainable and resilient infrastructure construction on peatlands.

Furthermore, traditional bearing capacity models do not apply to infrastructures founded on peat and CLARIFIER contributes to the understanding of failure mechanisms in these materials under lightweight embankments from sawdust and sand. Different to natural sands and gravels that are in short supply in most European countries, sawdust is generally available and thus costs are low. Its limited weight makes it attractive to explore for use as a fill material for construction in peat areas. The aim is to maximise the use of sawdust and minimise the use of natural sand in these constructions.

Facility Details
Name Deltares Geo Centrifuge
Owner Deltares
Location Delft, Netherlands
Website Click Here to Visit Site
Contact Suzanne van Eekelen
Head of facility Harm Aantjes

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