Experimental setup for simulating explosions on a reduced scale

Exploring the response of structures to explosions presents significant challenges when relying solely on numerical and analytical tools. To enhance our understanding and validate existing models, it is crucial to complement these tools with experimental tests. However, the availability of experiments specifically tailored for blast scenarios remains limited compared to tests conducted under other dynamic conditions, such as earthquakes. This scarcity can be attributed to the numerous complexities associated with conducting full-scale blast experiments, primarily due to the nature of the loading action involved.
Nevertheless, reduced-scale experiments provide an alternative approach that offers greater flexibility. In this context, the device in question opens up groundbreaking opportunities by enabling us to carry out experiments specifically designed to study the dynamic behavior of structures subjected to blast actions. For the first time, this device empowers us to explore and draw valuable conclusions from reduced-scale experiments that accurately simulate blast scenarios.
Further reading

Double shear apparatus for earthquake control

This innovative device provides a platform for conducting groundbreaking experiments, which aim to control the unstable slip of earthquake fault analogs, within the controlled environment of a laboratory. This is accomplished through the use of two distinct loading systems, each serving a specific purpose. The first system applies shear stress and is controlled by the vertical loading mechanism, while the second system applies normal stress and is controlled by the horizontal loading mechanism, allowing for comprehensive testing of the sheared interfaces.
Together, these two loading systems offer a powerful toolset for conducting experiments that push the boundaries of knowledge regarding the control of unstable slip in earthquake fault analogs. This device enables researchers to simulate fluid injection/extraction processes and replicate the stored energy within the earth's crust, contributing to a deeper understanding of seismic phenomena and facilitating the development of effective strategies for mitigating the impact of earthquakes.
Further reading

Simple shear Apparatus

The main purpose of a simple shear apparatus is to investigate the mechanical properties, behavior, and response of materials under shear loading conditions. It is commonly used in geotechnical engineering and soil mechanics to study the shear strength, deformation characteristics, and failure mechanisms of soils, rocks, and other granular materials.
By subjecting the specimen to controlled shear stress, researchers can measure parameters such as shear strength, shear modulus, and shear strain, as well as observe the development of shear bands, strain localization, and failure modes. This information is essential to understand the stability and performance of various materials and to develop models and design criteria for structures and geomechanics applications, including foundations, slopes, retaining walls, and tunnels.
Overall, the simple shear apparatus plays a crucial role in advancing our understanding of material behavior under shear stress, contributing to the development of safer and more efficient engineering practices.

Triaxial apparatus for partially saturated soils

This recently-acquired Bishop and Wesley triaxial apparatus for tests on unsaturated soils is a so-called double-wall testing machine, as the sample is placed within a bell filled by water and the ensemble bell/sample is placed in the pressurized chamber. This provides measures of volume change and indirectly of the degree of saturation. The device applies air and water pressures at both the base and the top of the sample in order to reduce testing time. The machine is equipped with special membranes in order either to use Bender elements to monitor the evolution of the elastic parameters (in particular the shear modulus), or to get porewater pressure measurements directly along the surface of the soil sample.
The first application of the system concerns the calibration of the constitutive soil models incorporating suction/saturation dependency. A more exploratory research activity involves the analysis of the triggering of a heterogeneous response within a sample under triaxial loading condition, in a partially saturated state, in terms of damage (captured via the evolution of the shear modulus) and porewater pressure evolution.

Biaxial apparatus for partially saturated soils

The biaxial machine BIAX is a unique piece of apparatus, designed at Centrale Nantes, to simulate at laboratory scale, the propagation of fluid flow through a partially saturated medium, under hydro-mechanical loadings. This machine, supplied by Megaris Srl and derived from the classical Bishop-Wesley device, is unique: besides being a suction-controlled biaxial equipment, it is characterized by special features such as the see-through nature of the main sides of the in-placed specimen, and consequently the customized way for loading mechanically a non-wrapped sample. The purpose of this design is: (i) to visualize the infiltration of a wetting/non-wetting fluid into a geo-material initially saturated by a non-wetting/wetting fluid, so as to characterize imbibition/drainage conditions, (ii) to identify the unstable regimes of this two-phase fluid percolation, the so-called fingering process, (iii) then to quantify a full-field fluid-driven deformation and track the moving interface. Apparently, the investigation in this field of tests requires, in parallel, a reliable optical system that will play a major role in the data extraction and exploitation.
Experimental campaigns using this apparatus are envisaged to characterize the behavior of soils with respect to pollutant infiltration, but also underground energy storage, in particular the analysis of tightness conditions of the caprock of underground aquifer with respect to leakage of the stored hydrogen/hydrocarbon, reactivation of existing fractures or triggering of new ones.
Further reading

3D printing for exploring new ideas and printing samples

3D printing has transformed the exploration of new ideas and sample production. Its ability to rapidly produce physical prototypes allows for quick iteration and experimentation, enabling us to visualize and evaluate concepts more efficiently. Additionally, 3D printing offers a cost-effective and efficient solution for producing samples for testing and validation purposes in our laboratory.
Furthermore, the capacity of 3D printing to create complex geometries and intricate designs opens up new possibilities in experimental geomechanics. Its additive layer-by-layer approach allows for the production of structures with fine details, internal cavities, and shapes that were previously challenging or impossible to achieve.

Direct shear apparatus with controlled temperature and fluid pressure

Direct shear apparatus with controlled temperature and fluid pressure is a specialized laboratory instrument used to study the behavior of soils, rocks, and other granular materials under shear stress while also controlling temperature and fluid pressure conditions.
The apparatus consists of two parallel plates, similar to a standard direct shear apparatus. However, it includes additional features for controlling temperature and fluid pressure within the specimen during testing. These features allow researchers to simulate specific environmental conditions or investigate the effects of temperature and fluid pressure on the material's behavior.
By applying controlled temperature and fluid pressure conditions during direct shear tests, researchers can gain insights into the material's response and better understand its behavior in real-world scenarios. This information is crucial for engineering design, risk assessment, and the development of appropriate mitigation measures in various geomechanics projects.
Further reading
  • Vasilescu A-R, Design and execution of energy piles : Validation by in-situ and laboratory experiments, PhD EC Nantes, 2019
  • Yin K., Vasilescu R., Fauchille A-L., Kotronis P. Thermal effects on the mechanical behaviour of Paris green clay – concrete interface. 2nd International Conference of Energy Geotechnics, ICEGT-2020, La Jolla, California, USA, April 10-13, 2022.
  • Yin K., Vasilescu A.R., Fauchille A-L., Kotronis P. 'Influence des cycles thermiques à l’interface argile verte/béton pour les pieux énergétiques'. 11èmes Journées Nationales de Géotechnique et de Géologie de l'Ingénieur, 28 - 30 Juin, Lyon, 2022.

Seismic table

This laboratory instrument is used for simulating earthquake vibrations and studying the behavior of structures and materials under seismic conditions. It allows researchers to subject scaled models and specimens to controlled vibrations that replicate the motions experienced during earthquakes. The table is primarily utilized in earthquake engineering research to understand structural dynamics, assess seismic performance, and investigate material behavior. It helps researchers analyze natural frequencies, mode shapes, damping characteristics, and other dynamic properties of structures and soils. Additionally, it enables the evaluation of structural integrity, failure modes, and the effectiveness of seismic design and retrofitting strategies.
Overall, the small seismic table serves as a valuable tool in earthquake engineering, enabling us to gain insights into how structures and soils respond to seismic forces. By conducting experiments on the table, we can improve seismic design methodologies, validate computational models, and enhance our understanding of structural behavior during earthquakes.
Published on July 17, 2023 Updated on February 26, 2024