As part of the GEOLAB project, the Institute of Geotechnics of TU Darmstadt is calling geotechnical engineers from industry and academia to participate in an international Blind Prediction Contest (BPC) on the response of piles under monotonic and cyclic lateral loading. Two separate tests will be performed on a hollow open-ended steel pile embedded in dry sand. One test under monotonic loading and the other under quasi-static harmonic loading with more than 10,000 loading cycles.
Contestant teams can submit predictions for both tests or for the monotonic test only. The predictions will be objectively marked based on their discrepancy with the experimental values. The teams with the higher score in the prediction of each test will be publicly announced. The rest of the submitted predictions will be anonymised and used for assessing the state of the art and the state of practice by the organiser committee.
General information on the tests and the BPC is made available below. More detailed information will be published with the opening of the event on 6 May 2024.
Pile test setup
Two tests will be performed at the TU Darmstadt Geotechnical Test Pit. The setup to be used in both tests is schematically depicted in the figure below. It consists in a 3 m hollow steel cylinder embedded 2 m in a dry compacted, very dense medium coarse river sand. In both tests, the pile will be loaded laterally at 0.58 m above the sand level. Detailed drawings of the pile and the connection between the pile and the hydraulic actuator will be published with the opening of the event on 6 May 2024.
Loading stages
The loading sequence for each test will be as follows:
Test 1 (Monotonic)
Stage 1: Controlled displacement at a rate of 1mm/ min up to a displacement of 20 % of the pile outer diameter (OD) measured at the loading point.
Stage 2: Switch to controlled force, maintaining the achieved force constant for 20 minutes or until the displacement rate is lower than 0.02 mm/min, whichever occurs last.
Stage 3: Switch to controlled displacement at a rate of -1 mm/ min until the applied force becomes null.
Test 2 (Cyclic)
Stage 1: Controlled displacement at a rate of 1 mm/ min until reaching a reaction force of 20 % of F10 %, where F10 % is the reaction force in Test 1 at a displacement of 10% of the pile OD measured at the loading point.
Stage 2: 10,000 cycles, with frequency of 0.1 Hz, from 10 % to 30 % of F10 %.
Stage 3: Unloading to zero at a rate of – 1 mm/min (controlled displacement).
Stage 4: Cycling loading, with frequency of 0.1 Hz, from 30 % to 70 % of F10 % until failure, defined as a displacement at the loading point of 20 % of the pile OD.
Stage 5: Unloading to zero load at a rate of – 1 mm/ min (controlled displacement).
Pile test instrumentation
The pile test will be instrumented as follows:
- 1 force transducer at the connection between the pile and the hydraulic actuator
- 9 displacement transducers conveniently located around the loading point to register X, Y , Z displacements and rotations.
- 32 strain gauges attached to pile in 4 longitudinal lines
Sand characterisation tests
The sand is being extensively characterised with laboratory tests, including monotonic (drained and undrained) and cyclic triaxial tests. In addition, a standard Cone Penetration Test will be performed to characterise the sand condition in depth after compaction. All the produced data will be made available for the participants with the opening of the event on 6 May 2024.
The guidelines of the BPC are given below. Detailed rules of the events will be published with the opening of the event on 6 May 2024.
Contestant teams
The contestant teams may consist of one or more members.
An individual can only be involved in a single team.
Except for category winners (monotonic/cyclic), all participants will be kept anonymous. For the publication of the predictions, teams will be identified by an inscription number which will be informed to the team members in advance.
There is no limit in the number of members of a team but teams with more than one member will designate a corresponding author for communication.
The contestant teams will be required to subscribe to one of the following groups:
a. Researchers
b. Practicing Engineers
Individuals from TU Darmstadt or other organisations, who are familiar with or has witnessed the tests are not allowed to participate.
Teams will be required to fill a template document with a brief description of the methods used for their predictions. All methods (empirical, analytical or numerical) are welcome.
Input data
Detail input data will be published in the event website on 6 May 2024.
Provided input data will include at least:
- Construction drawings and relevant photographs, specifying all necessary geometry and dimensions
- Detailed loading sequences
- CPT profiles of the sand pit before testing
- Sand characterisation tests, including particle size distribution, oedometric compression tests, drained and undrained monotonic triaxial tests (with different confining pressures and sand densities), and cyclic triaxial tests
Predicted Quantities
The contest will have two categories: “monotonic pile test” and “cyclic pile test”.
All contestant teams must submit a prediction for the monotonic test. Predictions for the cyclic test are optional.
The participants are required to predict the following experimental results:
Monotonic test
Stage 1: Horizontal reaction force, pile head rotation, and pile bending moment at given imposed displacements between 0 and 20% of the pile OD.
Stage 2: Horizontal displacement at the end of the stage.
Stage 3: Unrecoverable horizontal displacement after unloading.
Cyclic test (Optional)
Stage 2: For the first cyclic loading package: minimum and maximum displacement after specific numbers of cycles.
Stage 3: Unrecoverable displacement after the first complete unloading.
Stage 4: For the second cyclic loading package: number of cycles required until the pile failure, defined by a deflection criterion..
Stage 5: Unrecoverable displacement after the second complete unloading.
Evaluation
For each quantity, the error is defined as the absolute value of the difference between the measured value and the predicted value.
The winner team for each category will be determined based on a single overall error indicator to be calculated as a weighed summation of the partial prediction errors. The error on the predicted values for Stage 1 of the Monotonic Tests, and Stages 2 and 4 of the Cyclic Tests will account for most of the final scores. The exact procedure to calculate the overall error will be informed with the opening of the event on 6 May 2024.
If there are sufficient (based on the judgement of the evaluation committee) participants in each group (Researchers and practicing Engineers), there will be one winner for each of the two groups. Otherwise, no distinction will be made between the two groups in announcing the winners.
The scores of all teams will be published identified only by the inscription number. The experimental data will be published simultaneously, in order to allow the teams to verify the calculation of the scores.
- The winning teams will be publicly announced in the event website and through social media channels.
Analysis and publication of the BPC
- The Organising Committee will prepare an international journal paper comparing and analysing the received predictions, with the goal of assessing the state of art and the state of practice. By participating the BPC, the team members authorise the use of the submitted data for that purpose. The participants BPC will not be invited as co-authors of this paper.
- The contestant teams are free to publish their predictions in separate papers using the experimental data provided, as long as the source is properly acknowledged.
Updated information on the BPC will be published in the event website until the announcement of the winner teams. If you would like to receive the updates via email, please sign in here for the BPC mailing list.
A webform will be made available on 6 May 2024 for the submission of predictions and the registration of the authors.
18 Mar 2024: First announcement and newsletter registration opening
06 May 2024: Publication of supporting documentation and opening of submission period
15 Sep 2024: Closure of the submission period
28 Oct 2024: Announcement of the BPC winners
Organising Committee
Prof. Dr.-Ing. Hauke Zachert
Dr.-Ing. Jan Machaček
Dr.-Ing. Joaquin Liaudat
GEOLAB Project
The GEOLAB project is a collaborative initiative aimed at advancing geotechnical research and innovation through cutting-edge laboratory facilities and interdisciplinary cooperation. The GEOLAB project, funded by the European Union H2020 Research and Innovation Programme, spans four years from 2021 to 2025. The ten GEOLAB partners offer access to a wide range of experimental facilities, including:
- University of Maribor Large-scale Triaxial Apparatus
- Technical University of Darmstadt Pile Foundation Test Pit
- ETH Zürich Beam & Drum Centrifuge
- Norwegian Geotechnical Institute Geotest Sites
- Deltares GeoCentrifuge and GeoModel Container
- University Of Cambridge Schofield Centre
- TU Delft Geotechnical Centrifuge and Liquefaction Tank
- CEDEX Track Box
- Gustave Eiffel University Geotechnical Centrifuge
