Mimikawa River with seven dams and power stations in operation runs in the eastern area of Kyushu. With a total output of 341MW, the river basin is an important hydro-energy source in the Kyushu region. Typhoon No. 14 in 2005 brought record-breaking heavy rainfall, causing severe slope failures in approximately 500 locations. This experience raised awareness of the potential risk of slope failures which might occur in Mimikawa River Basin. Kyushu Electric Power owns hydroelectric power stations distributed over a wide area in this basin. From the viewpoint of appropriate dam operation, facility maintenance, and medium-long term installation, it is essential to understand the future risk of disaster due to slope failures, in advance, and optimally control this risk. However, because the slope failure phenomenon is very complex, and occurs over a wide area of the Mimikawa River Basin, there are no established methods to predict or manage these failures. The unprecedented Typhoon No. 14 disaster experience has provided key data for future slope failure prediction. By carrying out investigations such as a wide-area survey of slope failures, characteristics of slope failures including the locations, scales, failure mechanism and the level of rainfall that causes failure were clarified. In addition, through the use of information obtained from records of past disasters, a simplified method for wide-area slope failure prediction based on the characteristics of the river basin was structured. And through the use of this information and this method, the authors sought to identify slopes for which failures might occur and the level of rainfall that would cause failure (risk map). One example of specific hydroelectric installation risk management was also considered.
This article summarizes the paper receiving the frontier award from the Japanese Society for Rock Mechanics (JSRM) in the fiscal year of 2014. Seafloor hydrothermal deposits have been found to be widespread in the waters off Okinawa Island. To assist with the design and manufacture of mining and crushing machinery and ore transportation equipment, this study investigated the mechanical properties of these seafloor hydrothermal deposits. Tests were carried out on the strength, hardness, and abrasiveness of boring cores and block samples of the deposits. In a uniaxial compression test, in which a specimen was crushed to 20% of its initial height, the size of the debris was slightly smaller than tuff, andesite, and sandstone. The specific energy calculated from the boring data was found to be closely related to the mechanical properties of the hydrothermal deposits, and its distribution beneath the seafloor was determined from boring data. The results obtained in this study provide important guidelines for the future development of mining techniques for seafloor hydrothermal deposits.
In a mountain tunnel construction project, the precise evaluation and prediction of ground conditions ahead of the tunnel face are necessary for the installation of proper auxiliary methods and the validation of designed support patterns. This could lead to a cost optimization and safety construction. In order to predict the ground condition, the authors have developed an inclination monitoring system, comprising a small-diameter tilt sensor named TT-Monitor (Tunnel Tilt Monitor), the evaluation methodology of measurement data, and the visualization of prediction results. This paper describes an overview of the forward prediction mechanism by means of three-dimensional numerical analysis. It then illustrates the way to measure and evaluate the inclination angle by the TT-Monitor with the tunnel advance. Lastly some typical results of a field demonstration test are presented. The results clearly show the validation and applicability of our proposed methodology
A new rock classification named as Rock Mass Quality Rating (RMQR) proposed by the authors (Aydan et al. 2013). This new rock classification quantify the state of rock mass and possible geo-mechanical properties of rock masses can be estimated using the classification system together with intrinsic geo-mechanical properties of intact rock. This system eliminates some shortcoming of previous systems. It is correlated with existing quantitative rock classification systems as well as qualitative rock classification systems used in Japan. The fundamental parameters of this system are explained and the correlations with quantitative and qualitative systems are presented. Further applications of this new system are pointed out.