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Mizutani S.,Kawasaki Geological Engineering Co.
Journal of the Geothermal Research Society of Japan | Year: 2016

The geological assessment of fractures, which usually play a role of paths of geothermal fluids and intrusive rocks, and consequently relate to heat sources and reservoirs, is essential to explore geothermal resources. This paper aims to assess the characteristic of the intrusions such as depth, magnetization, age and so on in the geothermal prospective area. A method of its assessment in this paper is proposed using the integrated analysis of gravity and geomagnetic data sets. The two-layers model consisting of basement and overburden sediment rocks, where dikes and sheets intrude, is applied. According to Poisson's theorem, the gravity and geomagnetic data sets will be plotted linearly in the area where the contrast of density and magnetization is uniform. If the data are collected widely enough over the studied area, the linear gravity-geomagnetic correlations arising from the effects of the two-layers model are obtained, implying that their elimination makes a proper estimation of magnetic effects from such intrusive rocks as dikes and sheets which distribute locally. Three methods, the histogram cross-plot, individual cross-plot and the gravitational-magnetic correlation efficient calculated by the Moving Window Poisson's method, were applied. The regional linearity of the twolayers model and sporadic locality of the volcanic area are certified. The result of the study in the central Hokkaido in Japan reveals that the NE-SW direction of strike-slip faults is present which is concordant with that of the stress field in the studied area. This may also support to the former study of the relationship between possible fracture distribution and compressive stress field in the geothermal prospective area. And the small uplifts and depressions along the faults can be analyzed by gravity and geomagnetic data respectively. © The Geothermal Research Society of Japan, 2016.

Zhao Z.,ION GXT Imaging Solutions | Zhao Z.-X.,Chinese Academy of Geological Sciences | Xu J.-R.,Chinese Academy of Geological Sciences | Ryuji K.,Kawasaki Geological Engineering Co.
Jilin Daxue Xuebao (Diqiu Kexue Ban)/Journal of Jilin University (Earth Science Edition) | Year: 2011

The quantitative velocity surveys have been carried out by explosion seismic tomography in several geologic settings. According to object, high resolution surveys can be obtained by designing source frequency, spatial distributions of source and receiver. The results show that the explosion seismic tomography technique can perform structure surveys at different depths in the sea or mountain regions. The investigation depth can extend to the Moho discontinuity. The resolution can as high as 3 m/s in mountain region. The new travel time tomograpic technique combined by refraction and reflection has been employed to the survey in Kyusyu sea region, Japan. The P wave arrival times received from 15 seismic surveys were used in the structure analysis of the 2-D profile. The velocity structure obtained from the tomographic techniquey shows an evident lateral heterogeneity. The velocity abnormal areas of arbitrary shape, such as thrust fault, resource cabin structure, emerge in the contours. It implies that the tomographic technique can character complicate geological structures. The validity of the technique can be expected for the geological structure analyses, the environment engineering and resource explorations in the sea and mountain regions. The result shows the tomography technique has an acceptable computation convergence velocity and stability.

Inagaki Y.,Public Works Research Institute | Tsukamoto M.,Kawasaki Geological Engineering Co. | Sasaki T.,Public Works Research Institute | Kawasaki S.,Hokkaido University
ISRM International Symposium - 8th Asian Rock Mechanics Symposium, ARMS 2014 | Year: 2014

In taking measures to prevent damage to existing structures by liquefaction, new techniques to improve the ground immediately under an existing structure without dismantling or removing the structure are currently being sought more enthusiastically than before. As ground improvement techniques using microbial metabolism to promote the relatively slow solidification of the ground, these are expected as suitable techniques for ground improvement under existing structures. Our research focused on the microbial carbonate precipitation (MCP), in which calcium carbonates precipitated from reactions between carbon dioxides and calcium sources by microbial metabolism binds soil particles and solidifies soil. In our research, sands solidified by MCP were subjected to cyclic triaxial tests to check their deformation characteristics. In addition, a dynamic centrifugal model test was conducted to check the effect of liquefaction countermeasure when the entire ground was solidified. © 2014 by Japanese Committee for Rock Mechanics.

Hitomi T.,Obayashi Corporation | Sasakura T.,Kajima Corporation | Yamaura M.,Chiyoda Corporation | Tozawa M.,Asano Taiseikiso Engineering Co. | And 3 more authors.
Energy Procedia | Year: 2013

For geological storage, as the small-scale distributed emission systems, CO2 micro-bubble storage (CMS) system may be suitable. To validate the feasibility of the CMS system, a numerical analysis was carried out. For the injection method and the targeted depth defined above, a unit comprising an injection well and four water pumping wells was modeled, The study showed a possibility of stable storage of CO2 in solution under the conditions of temperature, pressure and water chemistry at depths of 300 to 500 m, as long as full dissolution of CO2 gas with micro-bubbles is ensured.

Takamatsu K.,Japan Atomic Energy Agency | Takegami H.,Japan Atomic Energy Agency | Ito C.,Japan Atomic Energy Agency | Suzuki K.,Kawasaki Geological Engineering Co. | And 3 more authors.
Annals of Nuclear Energy | Year: 2015

One of the critical problems that have arisen from the accident at TEPCO's Fukushima Daiichi nuclear power plant is the removal of fuel debris. For solving this problem, an examination of the internal reactors has been planned to identify the fuel debris. However, the high radiation dose around the reactors has necessitated the development of a remote sensing method that would enable observation of the internal reactors from the outside. In our study, we focused on a nondestructive inspection method by which cosmic-ray muons could be used to observe the internal reactor from outside the reactor pressure vessel (RPV) and containment vessel (CV). We conducted an observation test on the high-temperature engineering test reactor (HTTR) at the Japan Atomic Energy Agency to evaluate the applicability of the method to the internal visualization of a reactor. We also analytically evaluated the resolution of existing muon telescopes to assess their suitability for the HTTR observation, and were able to detect the major structures of the HTTR based on the distribution of the surface densities calculated from the coincidences measured by the telescopes. Our findings suggested that existing muon telescopes could be used for muon observation of the internal reactor from outside the RPV and CV. © 2014 Elsevier Ltd All rights reserved.

Kasahara J.,Tokyo University of Marine Science and Technology | Kasahara J.,Kawasaki Geological Engineering Co. | Aldamegh K.,King Abdulaziz City for Science and Technology | Alanezi G.T.,King Abdulaziz City for Science and Technology | And 5 more authors.
Energy Procedia | Year: 2015

We developed time-lapse technology using the Accurately Controlled Routinely Operated Signal System (ACROSS) and seismic arrays and carried out field operations at the Al Wasse water pumping field in Saudi Arabia. We analyzed 2 months of data obtained in this field experiment. All of the data from 31 seismic stations showed very clear waveform changes during periods of several days. We also studied seismic interferometry using traffic noise. © 2015 The Authors.

Kikuyama H.,A TiC Co. | Ota S.,Kawasaki Geological Engineering Co.
ISRM International Symposium - 8th Asian Rock Mechanics Symposium, ARMS 2014 | Year: 2014

The results of drill core observation are among the most important basic data for geological survey; however, these results tend to include subjective aspects, because the core sample is qualitatively evaluated through macroscopic observation by engineers with different skill levels. Similarly, the classifications of strata, rock hardness and degree of weathering, which are derived from the results of drill core observation, tend to be subjective and tend to depend on the abilities of the engineers involved in determining them. These subjective aspects sometimes result in differences in evaluations that make it difficult for others to understand the basis for evaluation. This study aimed at adding quantitative indexes to core observation. Measurements of magnetic susceptibility and color were done for drill cores of igneous rocks and sedimentary rocks. To examine the validity of the quantitative indexes, the results of classification of strata, rock hardness and weathering from the quantitative method were compared with those from conventional core observation. Magnetic susceptibility and color were measured using portable meters, which enabled onsite measurement. Examinations revealed that the differences in measured magnetic susceptibility and color correspond to the differences in strata, lithofacies, rock hardness and degree of weathering. In measurements using a magnetic susceptibility meter and a color meter, it was possible to qualitatively determine the borders between different types of rock, even when it was difficult to determine the border by macroscopic observation because the changes in the borders were gradual. Using measurements of magnetic susceptibility and color in combination made it possible to examine the results by comparing and supplementing the results from the two measurement methods. Measurements of magnetic susceptibility and color of drill cores showed that it was possible to use these measurement results as useful quantitative indexes for classifying strata, lithofacies, rock hardness and degree of weathering, for comparing multiple cores, which is conventionally done by visual inspection, and for determining the landslide slip surface. © 2014 by Japanese Committee for Rock Mechanics.

Abe T.,Nippon Expressway Research Institute Co. | Tsukamoto M.,Kawasaki Geological Engineering Co. | Yokota S.,Nippon Expressway Research Institute Co. | Tayama S.,Nippon Expressway Research Institute Co.
15th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2015: New Innovations and Sustainability | Year: 2015

Expressway embankments have collapsed in many locations in Japan recently because of torrential rains and earthquakes striking the areas. Because the soil from collapsed embankments contains much water, we have assumed that penetrating rain and groundwater affected the embankments, in some way, and led to the collapse. To reinforce the slopes and prevent such disasters, we have dug slits where are excavated at the foot of the slope and filled with crushed stones to reduce the water content ratio of the slope. To verify the effectiveness of this measure, we have conducted the following two tests. First, we conducted laboratory tests, changing the water content ratio, to examine the changes in the strength characteristics of the embankment soil. This test confirmed that soil strength weakens as the water content increases, even if compaction of the soil remains the same. For the second test, we made a 1/50-scale model embankment and carried out large-scale dynamic centrifugal force loading tests to verify the reinforcement effects of this measure. The test confirmed that embankments reinforced with the drainage works held down deformation to half of that of embankments which were not reinforced.

Katayama T.,Kawasaki Geological Engineering Co.
Concrete under Severe Conditions: Environment and Loading - Proceedings of the 6th International Conference on Concrete under Severe Conditions, CONSEC'10 | Year: 2010

Petrographic diagnosis of alkali-aggregate reaction in concrete was introduced. Combined use of polarizing microscopy and SEM-EDS analysis on polished thin section well identified the loci of alkali-silica reaction (ASR) of reactive silica minerals (cristobalite, tridymite) and interstitial glass in the volcanic aggregates in concrete. Slowly cooled volcanic rocks oversaturated with silica contained silica minerals, nearly comparable with the calculated normative quartz in CIPW norm. Interstitial glass in volcanic rocks becomes enriched in SiO 2 with diminishing content by cooling of magma, which suggests that reactive rhyolitic glass can be formed in andesite and even basalt oversaturated with silica. Fly ash glass in ASR-affected concrete was also analyzed. SEM-EDS analysis revealed compositional trend lines of ASR gel, which reflects position of gel, evolutionary stage and environments of ASR in concrete. © 2010 Taylor & Francis Group, London.

Katayama T.,Kawasaki Geological Engineering Co.
Cement and Concrete Research | Year: 2010

Typical examples of so-called alkali-carbonate reaction (ACR) in the Canadian field concretes in Ontario, CSA concrete prism, RILEM concrete microbars and RILEM mortar bar containing Pittsburg aggregate, were examined petrographically based on polarizing microscopy, SEM observation and quantitative SEM-EDS analysis of the reaction products. It was revealed that ASR gel was the main product responsible for the crack formation in concretes, and that this gel had a common nature to that in the typical ASR. That is, ASR gel presented distinctive compositional trend lines, passing from low-Ca ASR gel at [Ca/Si] = 1/2-1/6, [Ca]/[Na + K] = 1.0 to the "convergent point" with [Ca/Si] = 1.3-1.8, [Ca]/[Na + K] = 100 at which chemical equilibrium is attained with CSH gel. The so-called ACR is a combination of deleteriously expansive alkali-silica reaction (ASR) of cryptocrystalline quartz, and harmless dedolomitization which produces brucite and carbonate halo. In laboratory specimens, fine dolomitic aggregate undergoes dedolomitization, and brucite and ASR gel react to form non-expansive Mg-silicate gel on the dolomite crystals. This explains why the mortar bar produces smaller expansion than the concrete microbar, and why the reaction products are so minute that they escape attention by optical microscopy. As a crystalline counterpart, mountainite is a candidate for low-Ca ASR gel, while sepiolite is one for Mg-silicate gel. Concealed ASR was detected in ACR-affected field concretes undergoing ingress of deicing salt which formed Friedel's salt and Cl-doped CSH gel. Compositions of ASR products, methods of sample preparation and analysis for correct identification of ACR, and artifacts were critically reviewed. © 2009 Elsevier Ltd. All rights reserved.

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