Home / Information / Laboratories and Academic Staff / Earth Crust Engineering

Earth Crust Engineering

To make a continuous progress of human beings, new technologies to develop mineral and energy resources would be required considering the preservation of global environment and to utilize and maintain underground space. In our lab, by integrating rock fracture mechanics, rock friction dynamics, rock hydraulics, seismology, and so on, we intended to contribute to the development of new technologies to overcome various difficult conditions.

Academic Staff

Eiichi FUKUYAMA

Eiichi FUKUYAMA190408Professor (Graduate School of Engineering)

Research Topics

Large scale rock friction experiments and fault rupture simulation along complicated fault system have been conducted based on rock fracture mechanics and dynamics of rock friction to evaluate the strength of Earth's crust and stress applied there, whose information had been considered to be difficult to evaluate. Large scale friction apparatus is a very unique testing machine in the world. Using this apparatus, scale dependency of friction on the sliding surface size and detailed rupture front propagating along the fault have been studied. In addition, using boundary integral equation method, dynamic rupture propagation along complicated fault system can be achieved, which provides us with an information on the strength of the fault as well as the applied stress to the fault system. These may lead us to understand the evaluation of crustal rock strength.

Contacts

Room 355, Bldg. C1, Katsura Campus, 615-8540, Kyoto, Japan
TEL: +81-75-383-3209

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, 615-8540, Kyoto, Japan
TEL: +81-75-383-3210

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/