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Earth Crust Engineering

In order to make a continuous progress of human beings, new technologies to develop mineral and energy resources considering the preservation of global environment and to utilize and maintain an underground space would be required. In our laboratory, we intend to develop such new technologies, which can be applied to difficult and various conditions, by combining the knowledge of rock mechanics and seismological techniques. Among them, we focus to development of technologies for the geological disposal of carbon dioxide and nuclear waste, shale gas development, and safety mining of mineral resources in deep mines.

Academic Staff

Tsuyoshi ISHIDA

Tsuyoshi ISHIDAProfessor (Graduate School of Engineering)

Research Topics

I have made lots of researches on rock stress measurements and rock fracturing mechanism. Based on the research experiences, I hope to contribute to carbon dioxide underground sequestration projects and radio-active nuclear waste underground disposal projects, to solve the energy backend problems that are becoming serious problem for human beings.

Contacts

Room 355, Bldg. C1, Katsura Campus
TEL: +81-75-383-3209
E-mail: ishida@kumst.kyoto-u.ac.jp
http://geo.kumst.kyoto-u.ac.jp/lab/member/Ishida_t/English.htm

Yoshitaka NARA

Yoshitaka NARAAssociate Professor (Graduate School of Engineering)

Research Topics

When designing sub-surface structures in a rock mass, it is necessary to consider their long-term stability. For this purpose, understanding brittle deformation and fracturing in rock is essential. In order to contribute ensuring the long-term stability of structures in a rock mass, I am conducting studies related to rock mechanics and fracture mechanics. Specifically, I am investigating influences of environmental conditions (e.g., temperature, humidity, and water) on physical and mechanical properties of rock.

Contacts

Room 356, Bldg. C1, Katsura Campus
TEL: +81-75-383-3210
E-mail: nara.yoshitaka.2n@kyoto-u.ac.jp

Makoto NAOI

Makoto NAOIAssistant Professor (Graduate School of Engineering)

Research Topics

Study of microseismic events (Acoustic Emissions) and its relation to larger events in an effort to understand earthquake generation process and mitigate seismic risks in deep mines

Contacts

Room 354, Bldg. C1, Katsura Campus
TEL: +81-75-383-3211
E-mail: nara.yoshitaka.2n@kyoto-u.ac.jp

Research Topics

CO2 fracturing laboratory experiments to develop shale gas

We proposed a new method to extract shale gas (flammable methane gas) trapped in shale bedrock around 3000 m deep. Conventional method to extract shale gas is to make cracks by injecting water into hard shale bedrock, as shown in Figure 1. In the new method, CO2 (carbon dioxide) is used instead of water. Under the great depth, CO2 becomes supercritical state being very slick. Since we found that the supercritical CO2 can make finer cracks extending in larger area in our laboratory experiments (see Figure 2), we expect that CO2 produce more shale gas than water. In an arid region like a desert without water, this method has more advantage. In addition, since CO2 has higher affinity for shale than methane (CH4), CO2 sequestration also realized with enhanced recovery of shale gas. We will progress this research further and propose this method to all over the world.

Fig_CO2_1.png
Figure 1: Illustration of shale gas development by hydraulic fracturing

 Fig_CO2_2.png
Figure 2: Photo of the specimen and loading condition of the experiment. Open and closed circles indicate setting positions of AE(Acoustic emission) sensors.

Acoustic Emission monitoring in South African deep gold mines

We monitor very small seismic events, or Acoustic Emissions, in South African deep gold mines in which mining depth reaches 4 km under the ground surface nowadays. In such a deep mine, mining induces high stress concentration around mining excavation, resulting in large earthquakes up to Mw ~ 3 (typical rupture size ~ 200 m) or larger. The induced earthquakes, which often cause fatal accidents, are large risks for mining workers. Reducing such risks are the purpose of our study.

In addition, observations in deep mines provide a large advantage for the research of earthquake generation process. In mines, the area and timing of stress increase can be evaluated from a mining plan, and hence, we can deploy a seismic network near the source of future large earthquakes, which will be induced by mining. This advantage provides us to monitor very tiny signals that may radiate in earthquake preparation process.

Because induced earthquakes are large risks, mining companies deploy observation networks to monitor seismicity. These networks, however, typically target events larger than Mw –1 (typical rupture size ~ a few meters). This detectability is unlikely significant to investigate the relationship between large earthquakes causing fatal accidents and smaller seismic events, which may be useful to evaluate seismic risks as indicated from laboratory experiments. In order to study such relationship, we have deployed networks that can detect microseismic events down to Mw –5 (typical rupture size ~ a few centimeters). We are analyzing the data obtained by these observations to understand earthquake generation process and to reduce risks of fatal accidents in deep mines.

Fig_AE.png

Figure3: Hypocenter distribution of microseismic events observed by our AE (Acoustic Emission) network for research at 1 km depth in a mine. Left, all events. Right, events larger than Mw –1, which corresponds to the detection limit of typical networks in South African gold mines. Some event aggregations are recognized in the left that are not recognized in the right one.

Laboratory Website

http://geo.kumst.kyoto-u.ac.jp/lab/