Seismic investigation of the Excavation damaged zone in Opalinus Clay

Schuster, Kristof; Alheid, H.-J.; Böddener, D.

doi:10.1016/s0013-7952(01)00054-0

Cited by 55 publications

(27 citation statements)

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“…The principle of IVM is described briefly in Sect. 3.2 and in more detail in Schuster et al (2001) and Schuster (2012). Figure 4a-e presents the derived v p , normalized amplitudes of first-arrival P-wave phases, and the dynamic elastic parameters t dyn and E dyn obtained with IVM in borehole BHE-25 (location: HE niche, borehole drilled -90°down into the floor, approximately 45°with respect to the bedding planes.…”

Section: Seismic and Dynamic Elastic Parametersmentioning

confidence: 95%

High-resolution mini-seismic methods applied in the Mont Terri rock laboratory (Switzerland)

et al. 2017

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We present several mini-seismic methods developed and applied in recent years in the Mont Terri rock laboratory. All these applications aimed at correlating and interpreting seismically derived parameters with relevant rock-mechanical parameters and findings. The complexity of the local site setting always required very high spatial and parameter resolution. Both, seismic P-and S-wave velocities and dynamic elastic parameters, such as the dynamic Poisson's ratio t dyn and the Young's modulus E dyn , are used to characterise the Opalinus Clay under real in situ conditions. We were able to establish a correlation between static and dynamic elastic Young's moduli. We describe the extremely large, small-scale variability of seismic parameters normal and parallel to the bedding plane orientation and address the question of fracture detection. We also present examples of the characterization of excavation-damaged zones with seismic parameters, including extent as well as degree of damage, and compare these to geological and structural mapping. The evolution of borehole-disturbed zones (BdZ) was deduced from repeating high-resolution borehole measurements. Finally, we quantify seismic anisotropy at dimensions between several cm and tens of m.

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Section: Seismic and Dynamic Elastic Parametersmentioning

confidence: 95%

High-resolution mini-seismic methods applied in the Mont Terri rock laboratory (Switzerland)

et al. 2017

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“…Optical devices can be used for fracture detection in boreholes [3]. Seismic borehole probes have been developed to measure the seismic amplitudes and velocities along the borehole walls [4]. If several boreholes are available, the probes can be combined for cross-hole measurements to determine the seismic properties in between the boreholes.…”

Section: Introductionmentioning

confidence: 99%

“…Similar to applications at Earth's surface, seismic sources and receivers are mounted on the cavity surface to investigate the EDZ by tomographic inversion methods [5]. These seismic approaches are based on the fact that the EDZ can be defined through a strong seismic velocity gradient [4,5]. Cross-hole and surface seismic measurements consider the rock mass at different scales.…”

Section: Introductionmentioning

confidence: 99%

Seismic travel-time and attenuation tomography to characterize the excavation damaged zone and the surrounding rock mass of a newly excavated ramp and chamber

Krauß

Giese

Alexandrakis

et al. 2014

International Journal of Rock Mechanics and Mining Sciences

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Highlights: -4D seismic tomography is able to resolve rock-mass changes due to excavation work.-Attenuation tomography is more sensitive to changes than travel-time tomography.-Changes of rock-mass are not restricted to the new excavation.Keywords: mining, time-lapse tomography, excavation damaged zone, underground lab, attenuation Abstract:Seismic travel-time and attenuation tomography were applied to characterize the excavation damaged zone and the adjacent rock mass in the GFZ-Underground-Lab within the research and education mine Reiche Zeche of the Technical University Bergakademie Freiberg (Germany). The lab is situated in gneiss rocks at 150 m depth and comprises three galleries which enclose an area of approximately 50 m x 100 m. Along these galleries two seismic surveys were performed before and after the excavation of a new ramp and chamber. For both measurements, travel-time and attenuation tomographies for Pwaves were performed with the ray-based inversion algorithm SIMULPS14. The seismic velocities were calculated from first-arrival travel times whereas a logarithmic-spectral-ratio approach was used to calculate the corresponding quality factors (Q) for attenuation tomography. A comparison of the tomograms reveals a decrease of average P-wave velocity values from 5.64 km/s to 5.54 km/s and of average Q-values from 29.8 to 26.5 in the whole area after the excavation of the new cavities. The maximum changes are located at already weakened zones either at the conjunction of two galleries or of a major fracture zone with a gallery. The attenuation tomography shows a higher sensitivity to rock mass changes than the travel-time tomography. However, the calculation of the Q-values demands a higher signal quality than the determination of the seismic travel times.

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“…Also, the tunnel is surrounded by a simulated excavation damaged zone (EDZ). In agreement with common assumptions on the dimension of the EDZ ( [2], [3]), the modeled EDZ extends twice the tunnel radius into the surrounding formation and is approximated by a seismic velocity and density gradient. We applied a linear decrease of up to 20 % of the original random media formation velocities and density toward the tunnel surface (Fig.…”

Section: Fd Modelingmentioning

confidence: 80%

Realistic FD Modeling of the Tunnel Environment for Seismic Tomography

Jetschny¹,

Heider²,

Bohlen³

2011

First International Conference on Engineering Geophysics

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IntroductionEspecially in urban areas, tunneling is the method of choice to built new pathways to improve the infrastructure, for e.g. rail tracks, roads or power cables. In this context, safety threads are not limited to the tunneling construction itself but can occur years later. Cavities or fracture zones that can be weakened by the tunneling are a serious risk, both for the stability and integrity of the tunnel tube and buildings on the surface. A collapse of a cavity can result in sudden load peaks possibly overpowering the stability of the tunnel casing and subsidence damage to buildings and buried gas pipelines (Fig. 1). Seismic tomography is a useful tool to detect such anomalies in the vicinity of the tunnel tube while the tunneling progresses or after completion. In order to do so, seismic receivers can be placed at the tunnel wall or at anchors behind the tunnel wall. The seismic wave field is excited by a hammer blow applied to the tunnel wall. Basis for such a tomography is a profound understanding of the seismic wave propagation in the complex surrounding of a tunnel which can be gained from seismic modeling. We, therefore, investigate the influence of the excavation damaged zone (EDZ) that is usually present as a side effect of the tunneling and the topography of the tunnel wall. Both features will significantly effect the seismic waves excited at the tunnel wall. The modeling is done by the parallel elastic 3-D finite difference (FD) modeling code SOFI3D using a Cartesian coordinate system [1]. Later, we insert an anomaly close to the tunnel wall. This paper will now primary focus on the realistic description of a tunnel example and the accurate modeling of seismic waves with respect to this model.

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Seismic investigation of the Excavation damaged zone in Opalinus Clay

Cited by 55 publications

References 0 publications

High-resolution mini-seismic methods applied in the Mont Terri rock laboratory (Switzerland)

High-resolution mini-seismic methods applied in the Mont Terri rock laboratory (Switzerland)

Seismic travel-time and attenuation tomography to characterize the excavation damaged zone and the surrounding rock mass of a newly excavated ramp and chamber

Realistic FD Modeling of the Tunnel Environment for Seismic Tomography

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