Seismic Tomography Investigation in 140m Gallery in the Horonobe URL Project

2010 ◽  
Vol 1265 ◽  
Author(s):  
Yutaka Sugita ◽  
Takahiro Nakamura ◽  
Hiroyuki Sanada ◽  
Takao Aizawa ◽  
Shunichiro Ito
Keyword(s):  
Seismic Tomography ◽  
Seismic Velocity ◽  
Seismic Source ◽  
Small Scale ◽  
Energy Agency ◽  
Sedimentary Environments ◽  
Tomography System ◽  
Observation Area ◽  
In Situ Experiments ◽  
Underground Research Laboratory

AbstractThe Japan Atomic Energy Agency (JAEA) established the Horonobe Underground Research Laboratory (URL) Project at Horonobe, in Hokkaido, Japan to enhance reliability of nuclear waste disposal technologies to be developed in deep sedimentary environments. JAEA has undertaken a number of in-situ experiments to determine changes in the properties of the host rock and the extent of the excavation disturbed zone (EDZ) created by the excavation of underground galleries for the disposal of radioactive waste. This paper reports a seismic tomography survey (using a hammer seismic source) of the “140m Gallery” at a depth of 140m below the surface of the Horonobe URL. The observation area was 3m square on the horizontal plane along the sidewall of the 140m Gallery. The measurement was repeated with the progress of excavation of a tunnel. In this experiment, the distribution of seismic velocity in the rock around the new tunnel and its decrease as the tunnel was dug, were observed using a simple small-scale seismic tomography system. The data collected show that this system can be used to capture the EDZ around tunnels.

scholarly journals Upscaling THM modeling from small-scale to full-scale in-situ experiments in the Callovo-Oxfordian claystone

2021 ◽  
Vol 144 ◽  
pp. 104582
Author(s):  
D.M. Seyedi ◽  
C. Plúa ◽  
M. Vitel ◽  
G. Armand ◽  
J. Rutqvist ◽  
...  
Keyword(s):  
Full Scale ◽  
Small Scale ◽  
In Situ Experiments

Low Alkaline Cement Used in the Construction of a Gallery in the Horonobe Underground Research Laboratory

2010 ◽  
Author(s):  
Masashi Nakayama ◽  
Haruo Sato ◽  
Yutaka Sugita ◽  
Seiji Ito ◽  
Masashi Minamide ◽  
...  
Keyword(s):  
Fly Ash ◽  
Research Laboratory ◽  
Concrete Lining ◽  
Energy Agency ◽  
Tunnel Support ◽  
Long Term Stability ◽  
Alkaline Conditions ◽  
High Level ◽  
Underground Research Laboratory

In Japan, any high level radioactive waste (HLW) repository is to be constructed at over 300 m depth below surface. Tunnel support is used for safety during the construction and operation, and shotcrete and concrete lining are used as the tunnel support. Concrete is a composite material comprised of aggregate, cement and various admixtures. Low alkaline cement has been developed for the long term stability of the barrier systems whose performance could be negatively affected by highly alkaline conditions arising due to cement used in a repository. Japan Atomic Energy Agency (JAEA) has developed a low alkaline cement, named as HFSC (Highly Fly-ash Contained Silicafume Cement), containing over 60 wt% of silica-fume (SF) and fly-ash (FA). HFSC was used experimentally as the shotcrete material in construction of part of the 140m deep gallery in the Horonobe Underground Research Laboratory (URL). The objective of this experiment was to assess the performance of HFSC shotcrete in terms of mechanics, workability, durability, and so on. HFSC used in this experiment is composed of 40 wt% OPC (Ordinary Portland Cement), 20 wt% SF, and 40 wt% FA. This composition was determined based on mechanical testing of various mixes of the above components. Because of the low OPC content, the strength of HFSC tends to be lower than that of OPC. The total length of tunnel using HFSC shotcrete is about 73 m and about 500 m3 of HFSC was used. The workability of HFSC shotcrete was confirmed in this experimental construction.

scholarly journals Effect of centimetric freezing of the near subsurface on Rayleigh and Love wave velocity in ambient seismic noise correlations

2020 ◽  
Vol 224 (1) ◽  
pp. 626-636
Author(s):  
René Steinmann ◽  
Céline Hadziioannou ◽  
Eric Larose
Keyword(s):  
Surface Wave ◽  
Wave Velocity ◽  
Love Wave ◽  
Ambient Noise ◽  
Seismic Velocity ◽  
Environmental Parameters ◽  
Velocity Variation ◽  
Small Scale ◽  
Apparent Velocity ◽  
Velocity Variations

SUMMARY About a decade ago, noise-based monitoring became a key tool in seismology. One of the tools is passive image interferometry (PII), which uses noise correlation functions (NCF) to retrieve seismic velocity variations. Most studies apply PII to vertical components recording oceanic low-frequent ambient noise ( < 1 Hz). In this work, PII is applied to high-frequent urban ambient noise ( > 1 Hz) on three three-component sensors. With environmental sensors inside the subsurface and in the air, we are able to connect observed velocity variations with environmental parameters. Temperatures below 0 °C correlate well with strong shear wave velocity increases. The temperature sensors inside the ground suggest that a frozen layer of less than 5 cm thickness causes apparent velocity increases above 2  % , depending on the channel pair. The observations indicate that the different velocity variation retrieved from the different channel pairs are due to different surface wave responses inherent in the channel pairs. With dispersion curve modelling in a 1-D medium we can verify that surfaces waves of several tens of metres wavelength experience a velocity increase of several percent due to a centimetres thick frozen layer. Moreover, the model verifies that Love waves show larger velocity increases than Rayleigh waves. The findings of this study provide new insights for monitoring with PII. A few days with temperature below 0 °C can already mask other potential targets (e.g. faults or storage sites). Here, we suggest to use vertical components, which is less sensitive to the frozen layer at the surface. If the target is the seasonal freezing, like in permafrost studies, we suggest to use three-component sensors in order to retrieve the Love wave response. This opens the possibility to study other small-scale processes at the shallow subsurface with surface wave responses.

Resolving small-scale heterogeneities with dense non-hyperbolic seismic tomography

2006 ◽  
Vol 2006 (1) ◽  
pp. 1-4
Author(s):  
Brittan John ◽  
Yuan Jerry ◽  
Long Andrew
Keyword(s):  
Seismic Tomography ◽  
Small Scale

Fracture Strength Estimation of SiC Block for IS Process

2010 ◽  
Author(s):  
Hiroaki Takegami ◽  
Atsuhiko Terada ◽  
Kaoru Onuki ◽  
Ryutaro Hino
Keyword(s):  
Fracture Strength ◽  
Large Scale ◽  
Weibull Modulus ◽  
Reliability Assessment ◽  
Prediction Method ◽  
Scale Model ◽  
Small Scale ◽  
Energy Agency ◽  
Destructive Test ◽  
Small Scale Model

The Japan Atomic Energy Agency has been conducting R&D on thermochemical water-splitting Iodine-Sulfur (IS) process for hydrogen production to meet massive demand in the future hydrogen economy. A concept of sulfuric acid decomposer was developed featuring a heat exchanger block made of SiC. Recent activity has focused on the reliability assessment of SiC block. Although knowing the strength of SiC block is important for the reliability assessment, it is difficult to evaluate a large-scale ceramics structure without destructive test. In this study, a novel approach for strength estimation of SiC structure was proposed. Since accurate strength estimation of individual ceramics structure is difficult, a prediction method of minimum strength in the structure of the same design was proposed based on effective volume theory and optimized Weibull modulus. Optimum value of the Weibull modulus was determined for estimating the lowest strength. The strength estimation line was developed by using the determined modulus. The validity of the line was verified by destructive test of SiC block model, which is small-scale model of the SiC block. The fracture strength of small-scale model satisfied the predicted strength.

scholarly journals Continuous active-source seismic monitoring of C O2 injection in a brine aquifer

Geophysics ◽  
2007 ◽  
Vol 72 (5) ◽  
pp. A57-A61 ◽  
Author(s):  
Thomas M. Daley ◽  
Ray D. Solbau ◽  
Jonathan B. Ajo-Franklin ◽  
Sally M. Benson
Keyword(s):  
Seismic Velocity ◽  
Seismic Monitoring ◽  
Small Scale ◽  
Saline Aquifer ◽  
Observation Well ◽  
Velocity Change ◽  
Seismic Velocity Change ◽  
Fluid Sampling ◽  
Brine Aquifer

Continuous crosswell seismic monitoring of a small-scale [Formula: see text] injection was accomplished with the development of a novel tubing-deployed piezoelectric borehole source. This piezotube source was deployed on the [Formula: see text] injection tubing, near the top of the saline aquifer reservoir at [Formula: see text] depth, and allowed acquisition of crosswell recordings at [Formula: see text] intervals during the multiday injection. The change in traveltime recorded at various depths in a nearby observation well allowed hour-by-hour monitoring of the growing [Formula: see text] plume via the induced seismic velocity change. Traveltime changes of [Formula: see text] (up to 8%) were observed, with no change seen at control sensors placed above the reservoir. The traveltime measurements indicate that the [Formula: see text] plume reached the top of the reservoir sand before reaching the observation well, where regular fluid sampling was occuring during the injection, thus providing information about the in situ buoyancy of [Formula: see text].

Temperature, strain rates, and rheology: the key parameters controling strength variations in the Australian lithosphere

2020 ◽  
Author(s):  
Magdala Tesauro ◽  
Mikhail Kaban ◽  
Alexey Petrunin ◽  
Alan Aitken
Keyword(s):  
Heat Flow ◽  
Seismic Tomography ◽  
Seismic Velocity ◽  
Gravity Data ◽  
Geophysical Methods ◽  
The Other ◽  
Crust And Upper Mantle ◽  
Large Variability ◽  
Other Hand ◽  
Australian Plate

<p>The Australian plate is composed of tectonic features showing progression of the age from dominantly Phanerozoic in the east, Proterozoic in the centre, and Archean in the west. These tectonic structures have been investigated in the last three decades using a variety of geophysical methods, but it is still a matter of debates of how temperature and strength are distributed within the lithosphere. We construct a thermal crustal model assuming steady state variations and using surface heat flow data, provided by regional and global database, and heat generation values, calculated from existing empirical relations with seismic velocity variations, which are provided by AusREM seismic tomography model. The lowest crustal temperatures are observed in the eastern part of the WAC and the Officer basin, while Central and South Australia are regions with anomalously elevated heat flow values and temperatures caused by high heat production in the crustal rocks. On the other hand, the mantle temperatures, estimated in a previous study, applying a joint interpretation of the seismic tomography and gravity data, show that the Precambrian West and North Australian Craton (WAC and NAC) are characterized by thick and relatively cold lithosphere that has depleted composition (Mg# > 90). The depletion is stronger in the older WAC than the younger NAC. Substantially hotter and less dense lithosphere is seen fringing the eastern and southeastern margin of the continent. Both crustal and mantle thermal models are used as input for the lithospheric strength calculation. Another input parameter is the crustal rheology, which has been determined based on the seismic velocity distribution, assuming that low (high) velocities reflect more sialic (mafic) compositions and thus weaker (stiffer) rheologies. Furthermore, we use strain rate values obtained from a global mantle flow model constrained by seismic and gravity data. The combination of the values of the different parameters produce a large variability of the rigidity of the plate within the cratonic areas, reflecting the long tectonic history of the Australian plate. The sharp lateral strength variations are coincident with intraplate earthquakes location. The strength variations in the crust and upper mantle is also not uniformly distributed: In the Archean WAC most of the strength is concentrated in the mantle, while the Proterozoic Officer basin shows the largest values of the crustal strength. On the other hand, the younger eastern terranes are uniformly weak, due to the high temperatures.</p>

A small-scale numerical study of fault slip mechanisms using DEM

2020 ◽  
Author(s):  
Nathalie Casas ◽  
Guilhem Mollon ◽  
Ali Daouadji
Keyword(s):  
Numerical Study ◽  
Surrounding Medium ◽  
Computational Cost ◽  
Static Friction ◽  
Discrete Element Modelling ◽  
Small Scale ◽  
In Situ Experiments ◽  
Fault Gouges ◽  
Fault Network

<p>How do earthquakes start? What are the parameters influencing fault evolutions? What are the local parameters controlling the seismic or aseismic character of slip?</p><p>To predict the dynamic behaviour of faults, it is important to understand slip mechanisms and their source. Lab or in-situ experiments can be very helpful, but tribological experience has shown that it is complicated to install local sensors inside a mechanical contact, and that they could disturb the behaviour of the sheared medium. Even with technical improvements on lab tools, some interesting data regarding gouge kinematics and rheology remains very difficult or impossible to obtain. Numerical modelling seems to be another way of understanding physics of earthquakes.</p><p>Fault zone usually present a granular gouge, coming from the wear material of previous slips. That is why, in this study, we present a numerical model to observe the evolution and behaviours of fault gouges. We chose to focus on physics of contacts inside a granular gouge at a millimetre-scale, studying contact interactions and friction coefficient between the different bodies. In order to get access to this kind of information, we implement a 2D granular fault gouge with Discrete Element Modelling in the software MELODY (Mollon, 2016). The gouge model involves two rough surfaces representing the rock walls separated by the granular gouge.</p><p>One of the interests of this code is its ability to represent realistic non-circular grain shapes with a Fourier-Voronoï method (Mollon et al., 2012). As most of the simulations reported in the literature use circular (2D)/spherical (3D) grains, we wanted to analyse numerically the contribution of angular grains. We confirm that they lead to higher friction coefficients and different global behaviours (Mair et al., 2002), (Guo et al., 2004).</p><p>In a first model, we investigate dry contacts to spotlight the influence of inter-particular cohesion and small particles on slip behaviour and static friction. A second model is carried out to observe aseismic and seismic slips occurring within the gouge. As stability depends on the interplay between the peak of static friction and the stiffness of the surrounding medium, the model includes the stiffness of the loading apparatus on the rock walls.</p><p>The work presented here focuses on millimetre-scale phenomena, but the employed model cannot be extended to the scale of the entire fault network, for computational cost reasons. It is expected, however, that it will lead to a better understanding of local behaviours that may be injected as simplified interface laws in larger-scale simulations.</p>

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