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Saitama, Japan

Wu J.,Chongqing Three Gorges University | Feng S.-K.,Chuo Kaihatsu Corporation | Li H.-J.,China Three Gorges University
Yantu Lixue/Rock and Soil Mechanics | Year: 2011

Collecting the digital images of geological drilling holes and interpreting the underground geological structure is a new method of geological prospecting. The interpretation of structural planes on drilling holes images is usually done by hand; and results of interpretation may be quite different for different people. Automatic identification system of structural plane (AISSP) can process the digital images of drilling holes to get structural plane parameters automatically. First of all, the images conversion from RGB color space to HSV color space should be done to highlight the structural plane region. Secondly, the S component images are filtered and enhanced for the next processing step. After the image segmentation, the binary image edge will be extracted and thinned by image morphology method; and edges of the structural plane are effectively extracted. Finally, structure plane altitude and thickness parameters are obtained by the Hough transform of sine curve and identified edge points. As example, a real digital drilling hole picture is analyzed by AISSP and the space parameters of the 4 structural planes appearing in the picture are calculated. Compared with the results interpreted by people, the results from AISSP are more precise and unique. Source

Che A.,Shanghai JiaoTong University | Wang H.,Shanghai JiaoTong University | Feng S.,Shanghai JiaoTong University | Siguyama T.,Chuo Kaihatsu Corporation
Journal of Applied Geophysics | Year: 2014

An identification analysis method of the rock mass characteristics is proposed using microtremor measurements in the boring hole. The method is based on the assumption that the epicenter of incident waves of each observation point in the same boring hole almost agrees. And the calculations are deconvoluted by the multiple reflection theory. The procedure applicable to the identification of the average elastic characteristics of in situ rock masses is presented. It is based on the minimization of an error function representing the difference between microtremor measurements performed on the rock mass and the corresponding data obtained by a numerical analysis subjected to known external actions. The method requires the formulation of the elasticity inverse problem and is based on the least square minimization procedure. As an example the approach has been applied to the identification of the dynamic properties and the predominant characteristics of the rock mass underlying a deep excavated quarry in west of Shanghai city. The inverted rock mass characteristics are compared with the PS logs at the sites and show consistency, confirming that the proposed inversion is promising. © 2014 Elsevier B.V. Source

Uchimura T.,University of Tokyo | Towhata I.,University of Tokyo | Wang L.,Chuo Kaihatsu Corporation | Qiao J.,CAS Chengdu Institute of Mountain Hazards and Environment
Landslide Science and Practice: Early Warning, Instrumentation and Monitoring | Year: 2013

Monitoring and early warning is one of the most promising ways toward reduction of disasters induced by landslides and slope instabilities. Although less costly than construction of retaining walls and other mechanical measures, early warning has several problems to be overcome. First, it is often the case that the exact location of an unstable soil mass is not defined and hence the location of monitoring sensors cannot be decided. This problem can be solved by installing many low-cost sensors within a possibly unstable slope. The second problem concerns what information of slope should be monitored. The present study has developed a low-cost MEM sensor unit that can monitor slope deformation during heavy rainfall. A wireless network collects signals from the sensors periodically and helps the local government issuing an alert signal or emergency evacuation order, depending upon the progress of tilting. It is further important that the low cost of the sensors allow individuals to purchase personally and installs them in order to protect themselves from slope disasters. The developed equipments have been deployed in several slopes in the recent times for validation of their field performances. The present text reviews the obtained records and discusses their use for practice. © Springer-Verlag Berlin Heidelberg 2013. Source

Fujita K.,Tohoku University | Fujita K.,Chuo Kaihatsu Corporation | Asami R.,University of Ryukyus | Takayanagi H.,Tohoku University | Iryu Y.,Tohoku University
Island Arc | Year: 2015

In order to investigate biota and sedimentary facies, and to delineate processes of carbonate sedimentation in seagrass beds, we conducted sedimentological investigations along three onshore-offshore transects at two sites (Nagura and Yoshihara) on Ishigaki-jima, Ryukyu Islands. Along the transects, the seagrass beds extended seaward 20-40m from shore, and their widths parallel to the shore ranged from 60 to >110m. The seagrass was dominated by Thalassia hemprichii, Cymodocea rotundata and subordinate C.serrulata. Seasonal changes in seagrass coverage were evident, with mean coverage relatively higher in summer and fall (July and October) than in winter and spring (January and April). The surface sediment throughout the seagrass beds was dominated by medium to very coarse sand-sized bioclasts displaying grainstone/packstone fabrics. Bioclasts were dominated by corals and coralline algae, with lesser benthic foraminifers, mollusks, echinoids, and Halimeda. The grainstone/packstone was underlain by gravelly sediment with coral clasts, showing a rudstone fabric, at the Nagura Site. The lower part of the core sediment was blackened, indicating a reducing environment. Two dates of corals collected at the Nagura and Yoshihara sites (24.5cm and 16.5cm below the sea bottom) were 2781-2306 and 4374-3805 cal BP (2σ age range), respectively, suggesting extremely low sedimentation rates (<0.1mm/year). Sediment influx was higher during July-January than during January-July. The relatively large influx during summer and fall is caused by massive sediment transport during typhoons and storms. The total sediment influx (i.e., suspension-load sediment transportation) is 74-96kg CaCO3/m2/year at the Nagura Site and 21-57kg CaCO3/m2/year at the Yoshihara Site. Sediment influx was significantly greater in the seagrass beds than in surrounding areas, providing supporting evidence for an sediment trapping function of seagrass beds. Our data indicate that seagrass beds in the Ryukyu Islands are characterized by high sediment fluxes and extremely low sedimentation rates. © 2015 Wiley Publishing Asia Pty Ltd. Source

Uchimura T.,University of Tokyo | Lin W.,Chuo Kaihatsu Corporation
15th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2015: New Innovations and Sustainability | Year: 2015

Moisture content is the most important factor affecting the stability of slopes against heavy rainfall events. In most of risk management methods for slope disasters, the rainfall intensity is used as the dominant index to evaluate the probability of failure events in an area. However, each slope should have individual hydraulic characteristics, and its probability of failure should be different from other slopes even under the same rainfall conditions. Some slope may contain a lot of water quickly after starting of rainfall, while some slope may show quick drainage after it stopped to rain. Such individual properties of each slope can be evaluated by observing the time histories of moisture contents in the slope ground together with rainfall records. In this paper, an attempt to establish a mathematical model on drainage process in a slope ground is reported. There is a simple relationship between the current moisture contents and the drainage rate of moisture, although this relation is affected by the adjacent rainfall intensity. The drainage properties of a slope can be evaluated by watching the behaviors of moisture contents at rainfall events with relatively low intensity. And the model parameters obtained by such weak rainfall events can be used to estimate the drainage rate after heavy rainfall events with some correction of the parameters, by using real time monitoring system. Source

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