Nonlinear Resonant Ultrasound Spectroscopy (NRUS) is a fundamental technique for assessing elastic nonlinearity in materials, particularly those exhibiting elastic hysteresis. Such materials are also known to exhibit fast and slow dynamic response, which is evolving in time. In this study, we examine the interplay between slow and fast dynamic effects in NRUS measurements performed on a...
Concrete structures such as bridges and wind turbine towers are subjected to a significant number of load cycles throughout their service life. This repeated loading leads to progressive damage accumulation, commonly referred to as fatigue degradation. The evolution of fatigue damage in concrete is influenced not only by the amplitude of the applied stress or strain but also by the frequency...
Nonlinear elastic effects are ubiquitous in the Earth’s crust, often revealed by small temporal changes in seismic wave velocity. Being able to interpret these subtle changes is critical to help us assess the state of stress and associated seismic risk. The objective of this work is to unravel the physical mechanisms responsible for the nonlinear elastic response of rocks, and in particular to...
Nonlinear Coda Wave Interferometry (NCWI) is an effective technique for detecting closed cracks in complex materials such as concrete, often missed by conventional linear ultrasonic methods. Combining the sensitivity of Coda Wave Interferometry (CWI) with a nonlinear modulation effect induced by a pump wave, this method activates nonlinearities in materials. Pump waves are conventionally...
It is well known that the water saturation degree ($S_w$) can strongly affect the linear viscoelastic properties of siliciclastic sandstones, even at low values (a few % points). For example, the impacts on the linear $Q$ was already studied starting from the end of the ´970s, in relation to lunar samples measured in the lab. A decrease in linear moduli with increasing $S_w$ has been...
Rocks exhibit astonishing time dependent mechanical properties, like memory of experienced stress or slow dynamics, which refers to a transient recovery of stiffness after a softening induced by almost any type of loading. This softening and transient recovery is observed in the subsurface and in buildings after earthquake shaking, or in laboratory samples.
We investigate the anisotropy of...
Earthquakes induce transient mechanical damage in the subsurface, leading to postseismic hazards such as enhanced landsliding, with recovery often taking years to reach steady-state conditions. This behavior has been associated with relaxation, a phenomenon observed across a wide range of materials following strain perturbations. However, systematic controls on recovery duration in the shallow...
The data from numerous laboratory and field experiments demonstrate that the material recovery processes in these two cases have much in common. In particular, they may take much longer than the impact (slow time), and the recovery is mostly (not exclusively) logarithmic. The main difference is in the duration of this time. A typical recovery time in laboratory experiments is of the order of...
