New robust observables on Rayleigh waves affected by an underground cavity: from numerical to experimental modelling

Abstract

The investigation and monitoring of shallow hazards due to the presence of underground cavities remain a challenge for geophysical approaches. Thus, seismic surface waves have been tested in several recent research projects in order to detect and localize voids as well as to determine their geometries. Among these works, numerous numerical studies have proved the feasibility of Rayleigh waves to detect cavities. However, most imagery processes adapted to R waves are faced with difficulties when applying them to real data. This limitation points to a major problem: the interactions between Rayleigh waves and a cavity are complex, particularly in the case of dispersing and attenuating surrounding media. Here, a combined approach based on numerical and experimental data obtained in a reduced-scale measurement bench is conducted to better understand the seismic wave propagation phenomena involved in the presence of a cavity and define robust observables that can be used in field measurements. The observables bearing the cavity signature are studied qualitatively and quantitatively on numerical and experimental recordings. The latter take into account all the propagation phenomena involved. The observations are carried out on the vertical and horizontal component of the Rayleigh wave displacement. The selected observables are studied depending on nondimensional cavity's parameters versus the frequency, that is the wavelength-to-size ratio and the wavelength-to-depth ratio. The effects of the cavity's parameters on the observables show particularities as a function of these components, such as a higher rate of the amplitude on the horizontal component as well as a perturbation of the direct seismic surface wave amplitude above the cavity, also higher on the horizontal component. This latter feature is particularly visible on the variation of the elliptical particle motion recorded at the surface. It can be linked to the mode conversions that occur in the vicinity of the cavity and which predominate on the horizontal component when the signal is normalized.

Dispersion of Rayleigh Surface Waves and Electrical Resistivities Utilized to Invert Near Surface Structural Heterogeneities

“…The cavity with a rectangular cross-section is assumed air filled. The incident Rayleigh surface waves are back-scattered (reflected and diffracted) by the cavity structure [44][45][46][47][48]. The reflected surface waves travel in the reverse direction towards the source, which are not shown in Figure 2 (section marked as before).…”

A numerical study on effect of underground cavities on seismic ground response due to Rayleigh wave propagation

“…In recent years, surface waves have been the subject of many analytical and numerical seismic studies in civil engineering. These researches are mostly limited to realizing the subjects like diffraction of Rayleigh waves by surface topographic features [42][43][44][45][46][47], cavity detection [48][49][50][51], evaluating bending deformation of tunnel and lining response [36,37,[52][53][54][55][56], the response of high-rise structure, and soil-structure interaction [32,57,58]. Therefore, seldom studies are related to investigating the seismic interaction of surface waves with underground structures on the free surface ground motion.…”

Three-Dimensional Localization of Buried Polyethylene Pipes Using Acoustic Method

“…Different methods exist for locating buried pipes [ 1 ] and, more generally, for investigating near-surface structures [ 2 , 3 , 4 , 5 , 6 , 7 ]. The choice of method to locate buried pipes depends on the context.…”