"Ester"-A new ring-shear-apparatus for hydrate-bearing sediments

Area of Science:

• Geotechnical Engineering
• Geology
• Materials Science

Background:

• Investigating the mechanical behavior of hydrate- and ice-bearing sediments is crucial for understanding geological processes and engineering challenges.
• Existing apparatus may not fully capture the complex behavior of these materials, especially concerning phase changes during shear.

Purpose of the Study:

• To develop and present a novel thermostated ring-shear-apparatus for investigating hydrate- or ice-bearing sediments.
• To enable controlled formation, decomposition, and reformation of hydrates/ices during shear testing.
• To provide a tool for studying stress paths and large strain behavior in these complex materials.

Main Methods:

• A thermostated ring-shear-apparatus with a fluid inlet/outlet for pore fluid control and volume change measurement.
• Hydraulic loading system and a servo actuator for applying normal load and torque.
• Capability for shear rates up to 12.6 mm/s and torques up to 1440 N m.
• System designed for pressures up to 30 MPa.

Main Results:

• The apparatus successfully allows for the formation and controlled decomposition of hydrates/ices before, during, and after shear tests.
• Demonstrated capability for stress path investigations and large strain experiments.
• System performance validated through tests on hydrate- and ice-bearing sand samples.

Conclusions:

• The developed ring-shear-apparatus is a versatile tool for studying the behavior of hydrate- and ice-bearing sediments.
• It provides valuable experimental data for research and engineering applications in permafrost and hydrate-bearing formations.
• The system facilitates complex experiments simulating real-world conditions of hydrate/ice decomposition and reformation.