The Kumamoto earthquake Mj7.3（Mw7.0） occurred on April 16, 2016, centered in the Kumamoto area, and largescale of slope collapse broke out in the Aso Ohashi bridge area. In this slope collapse site, damages to any roads and railways were intense, furthermore, there was concern that a further slope collapse could occur by repeated aftershock. Therefore, it was required that the investigation and construction were carried out swiftly while ensuring safety. At this time, in the area of a collapsed slope where people could not enter, aerial laser measurements to contribute to the survey design along with photogrammetry and measurements by an UAV in accordance with the progress of construction have been conducted, as well as further surface exploration utilizing the above results, bedrock stability evaluations and so on have been realized. Also, the design of the size and the shape for the land retaining embankment, and also the excavation range for the earth removal work of the top of slope on the basis of the three-dimensional data that was made based on survey results and geological reconnaissance. These prevention works carried out safely by unmanned machinery, while monitoring the slopes by the field observation under the construction. These series of investigation, design and construction were conducted with using the ICT（Information and Communication Technology）.
Many hydropower plants of J-Power were constructed more than 50 years ago. The geological risk assessment of the unlined tunnel such as waterway tunnel has been carried out for the steady maintenance of these old power plants since 2015. The laser measurement by the Handheld Laser Scanner was conducted in the unlined tunnel to improve efficiency and accuracy of the geological survey for the geological risk assessment. This report describes the method and the results of the measurement.
Firstly, a preliminary measurement by the Handheld Laser Scanner was conducted in access tunnels with unlined parts of two underground power plants to confirm performance such as accuracy at the measurement. The accuracy of the measurement was within about 10 cm of actual measured value. Later, the Handheld Laser Scanner was applied to a collapsed unlined waterway tunnel. Surface roughness and discontinuities on the bedrock can be visualized by computer from the acquired high density point cloud data. As a result, it was possible to grasp three-dimensional shapes of the tunnel conveniently and efficiently. Furthermore, we confirmed that highly accurate geological model can be produced by combining geological observation.
The authors introduce the automatic displacement monitoring system for the large-scale landslide using GPS and the long term monitoring result. In this case, the adoption of a long-term monitoring system with GPS was examined to observe the movement of an active landslide before and after the countermeasure construction. However, because the object landslide slope was northward, the applicability evaluation by a manual observation was carried out beforehand. Moreover, the characteristic of the GPS interferometric positioning to the displacement monitoring was understood by the experiments. The GPS monitoring system was composed of the one datum point at the stable ground and the five moving points in the landslide area, and began the continuous observation in October, 2003. The power supply of each station was a solar battery. At first, the cellular phones were used for online data transfer, afterwards they were changed to the wireless LAN lines.
This system was able to clarify the large displacements by the heavy rain in 2004, and calming down of landslide activity according to the countermeasure construction. In addition, the effectiveness of the tropospheric delay correction that used meteorological data was shown to the annual change that appeared to the vertical component of the displacements.