2. Double direct configuration Room Temperature
Main type of experiments:
- Fault constitutive frictional properties (velocity steps and slide-hold-slide)
- Ultrasonic P- and S- Wave measurement
- Acoustic Emission during stick-slip experiments
- Fault constitutive frictional properties (velocity steps and slide-hold-slide)
- Ultrasonic P- and S- Wave measurement
- Acoustic Emission during stick-slip experiments
The double direct shear configuration consists of two identical granular gouge layers sandwiched in a three-block assembly, composed of two side stationary blocks and a central forcing block. The forcing blocks are equipped with grooves, 0.8 mm height and 1 mm spacing, perpendicular to the shear direction, to ensure shear localization within the gouge layers and to minimize boundary shear. We construct gouge layers using a precise leveling jig to obtain a uniform and reproducible layer thickness that can vary between 0.3 and 0.8 mm and a nominal frictional contact area of 5x5 cm2.
The material that we shear it is usually powdered from intact rocks to best simulate fault gouge. However, we can also work with intact rock pieces to reactivate the original structures formed during a fault zone lifespan.
To investigate the physical properties of rocks we are equipped with two pulse-recivers with 8 channels each to measure ultrasonic velocities of rocks and characterize P- and S- wave (and also Vp/Vs ratio). The high speed trigger system has allowed us to reveal reliable precursors to failure in the past (ref).
Acoustic emissions during rock deformation can allow us to understand earthquake physics and try to upscale from the lab to nature. In our lab we are equipped with a fast recording (up to 50MHz in continuous mode) acoustic emissions detector system with capability of 16 channels. Using acoustic emissions in combination with Machine Learning models can bring us to unprecedented discoveries. In our lab we are actively developing this approach to the best of our capabilities.