In order to conduct disaster-prevention inspections without overlooking falling-rock sources, in this paper, we aim to establish a disaster-prevention inspection method using microtopography highlight maps and verify its effectiveness. First, we create the map using the data obtained from a high-density aerial laser. In our study, measurements were carried out using a measurement helicopter loaded with a laser measuring machine capable of irradiating 80,000 to 400,000 points per second. For creating a microtopographical representation, grid data, contour maps, inclination-amount diagrams that calculate the amount of inclination for each grid datum and change the lightness accordingly to express the topography, and wavelet-analysis diagrams that emphasize the change in the unevenness through wavelet analysis, are generally used. However, it is difficult to extract sources of falling rocks, because it is impossible to express the topographic change point between the contour lines in a contour map. It is also difficult to distinguish between ridges and valleys in the inclination-amount diagram because there is no information indicating the height difference. Furthermore, it is difficult to distinguish the microtopography in the wavelet-analysis diagram, because there is no information indicating the height difference or inclination. Therefore, in this study, we created a microtopography highlight map by overlaying 50 cm of grid data, the inclination-amount map, contour diagram, and wavelet-analysis diagram created from the measured laser data. A field survey verified that, by using this map, it was possible to detect a steep cliff of height 2 m or more, which is a possible source of falling rocks. In our study, we were able to extract sources of falling rocks from a microtopography highlight map.
The necessity of tackling falling-rock projects is increasing, especially, because of the recent heavy rains and earthquakes in Japan. In September 2017, a man riding a bike in the Hualien County in East Taiwan was hit by a falling stone and died. To avoid such painful accidents, improvements in countermeasure projects for falling rocks are necessary.
In Japan's rock-fall countermeasure projects, visual tools (drawings) such as basic forest maps and aerial photographs are used to investigate slopes and grasp the locations of falling rocks. However, on slopes covered by trees, it is difficult to prepare a plan view by actual measurement. As a background of investigation using these drawings, this is because these can be made relatively easily. However, in the current countermeasure projects, it is difficult to grasp accurately the positions of the falling-rock origins, from the surveys using these drawings. This leads to a decrease in the investigation efficiency, which is caused by poor positioning accuracy during the survey and because of overlooking objects. In addition, there are problems related to the safety of investigators at the time of investigation, because survey routes must be selected using these drawings and reliable research routes cannot be obtained from them. To solve these problems, it is necessary to improve the accuracy of the drawings used for the survey.
Understanding of a post-closure geological environment around a large underground facility is important for the safety assessment of geological disposal of high-level radioactive waste. Japan Atomic Energy Agency (JAEA) has performed the GREET (Groundwater REcovery Experiment in Tunnel) at the Mizunami Underground Research Laboratory (MIU) to evaluate the environmental recovery process after closure.
In the GREET, a mock up test drift (Closure test drift; CTD) was filled with in-situ groundwater as a simulation experiment of drift closure. The CTD is located in fractured crystalline rock at 500m depth below ground surface and has a floodable volume of approx. 900m3. Information of fracture distribution has been obtained by borehole investigation and mapping of gallery walls. The change of hydraulic pressure, hydrochemical condition and rock deformation have been monitored in and around the CTD during the tunnel excavation and water-filling. In parallel to the in-situ investigation, we perform a Hydro-Mechanical-Chemical (HMC) coupled simulation to enhance the understanding of the recovery process in fractured granite.
This study presents the simulation results of excavation stage. The sensitivity analysis were conducted with homogeneous model based on the investigations before excavation of CTD for the rough setting of simulation conditions. In addition, we try to reproduce the detail of HMC process with heterogeneous models generated by discrete fracture network model. Comparison of simulated results with observed data leads to the conclusion that the range of change in inflow during excavation can be predicted. However, model update is necessary for prediction of groundwater chemistry and spatial distribution of abrupt change in the drawdown.
The Mizunami Underground Research Laboratory (MIU) is being operated by the Japan Atomic Energy Agency (JAEA), in the Cretaceous Toki Granite in the Tono area, Central Japan. The MIU project is a broad-based, multi-disciplinary study of the deep geological environment, providing a scientific basis for the research and development of technologies needed for geological disposal in crystalline rock. The MIU design consists of two shafts, and several horizontal research galleries (Figure 1). The geological settings around MIU site are summarized in e.g. Ishibashi et al., (2016).
Ueda, Kenji (INPEX Corporation) | Ono, Kenya (INPEX Corporation) | Fuse, Kei (INPEX Corporation) | Nonoue, Ayako (INPEX Corporation) | Furui, Kenji (Waseda University) | Mustapha, Hussein (Schlumberger) | Tsusaka, Kimikazu (INPEX Corporation) | Furuta, Kohei (INPEX Corporation) | Rodriguez-Herrera, Adrian (Schlumberger) | Makimura, Dai (Schlumberger) | Manai, Taoufik (Schlumberger) | Ito, Toru (INPEX Corporation)
The legacy of conventional fields has resulted in many low permeability reservoirs deemed sub-commercial without an appropriate stimulation strategy. With low permeabilities and potentially heterogeneous reservoir characteristics, an optimal development approach would highly depend on their specific reservoir properties that may well require stimulation methods other than hydraulic fracturing. In this paper, we present a fully integrated characterization and modeling workflow applied to the Kita-Akita oil field in northern Japan, demonstrating the screening process for multiple completion and stimulation methods in a highly heterogeneous, low permeability sandstone reservoir.
To select a best completion and stimulation candidate from multiple methods, we constructed an evaluation matrix including the maturity of technologies, applicability to our reservoir, productivity, and economics. Multi-branch type completions such as radial drilling and fishbone drilling, as well as hydraulic fracturing were simulated and subsequently compared based on their productivities. Especially for the radial drilling and the fishbone drilling, a 3D FEM model was built for their complex laterals, and the inflow performances were evaluated with homogenous reservoir properties, respectively. Besides, due to the highly heterogeneous nature of the reservoir, we built a full-physics subsurface model based on a pilot-hole data acquisition and legacy 2D seismic lines. The 3D model served as a canvas to assess reservoir flow and geomechanical behavior, calibrated with production history from past producing wells in the 1950's to 1970's. Based on these models, the best infill drilling location was selected and multiple well completion and stimulation practices were evaluated.
Through the screening methodology, the multi-stage hydraulic fracturing was identified as the best suited from an instantaneous productivity perspective. Yet, even though hydraulic fracturing would enhance the accessibility into multiple distinctively isolated sandstones occurring in the deepwater slope channel setting, the treatment costs exceeded the economic threshold significantly in our case. Inflow performance evaluation based on the 3D FEM modeling illustrates multi-branch type completions such as radial drilling and fishbone drilling were identified with a good stimulation skin factor. As a result of 3D simulation study, multi-branch completion was revealed as a technical and economically viable stimulation option in the heterogeneously distributed sandstone reservoirs.
The advent of recent completion and stimulation techniques now renders low permeability reservoirs with relatively large development potential. Even with the development challenges quite different from conventional reservoirs, the approach shown in this paper provides a helpful reference for the study and decision-making process when the legacy field needs an optimal stimulation strategy.
Response in a porous seabed under dynamic environmental loading is a vital engineering issue in marine geotechnics. Lots of investigations for seabed response under dynamic loading have been developed through mathematical, numerical and experimental approaches. Most previous numerical models for seabed response in marine environments were based on finite element models. In this paper, based on local radial basis function collection method (LRBFCM), a meshfree model is proposed for the seabed response in the marine environments. In the present model, partial dynamic approximation (u-p approximation) will be used, and three different types of natural loading will be considered, i.e., wave, current and earthquake loading.
In the last twenty years, more and more marine structures are constructed with the deeper exploration and study for the offshore area. The most important aspect to be considered in engineering practice is the stability after putting in use of those marine structures under the complicated environment loading. In general, three types of the environmental loading needs to be taken into account for the design of marine structures, which are ocean waves, currents, and probable earthquake respectively. The dynamic response under these loading has attracted great attention among coastal and geotechnical engineers due to the growth of activities in marine environments. As the conventional loading, how ocean wave and current affect the marine structure stability is a vital problem for coastal engineers.
In general, the propagating ocean wave will generate the dynamic pressure in the sea floor, which may trigger soil liquefaction of the seabed as reported in the laboratory test (Sassa and Sekiguchi, 1999). Meanwhile, the effect of earthquake is also important for engineering design. Although the probability of earthquake occurred nearby the marine structures is not so high, once the earthquake happened, the damage would be devastating.
As one of the major natural disasters need to be considered in structure design, earthquake is also able to liquefy the saturated soil through seismic shaking effect. The liquefaction phenomena induced by seismic wave was fully aware by the public from the Niigata earthquake in 1964 in Japan, which caused unprecedented damage. The problem of earthquake-induced liquefaction attracted a great deal of attention of geotechnical researcher and great achievements have been made in the past (Seed et al., 2003). However, as pointed by Ye and Wang (2015), most of the studies for earthquake loading are concerned with onshore structures, while only a few studies considered offshore structures whatever by experiment or numerical simulation. For the earthquake loading, Chen et al. (2018) has developed the analytical solution for layered porous seabed under vertical seismic motion.
Endo, Masashi (TechnoImaging) | Gribenko, Alex (TechnoImaging) | Sunwall, David (University of Utah) | Zhdanov, Michael S. (TechnoImaging) | Miura, Takuya (TechnoImaging) | Mochinaga, Hisako (University of Utah) | Aoki, Naoshi (JGI) | Mouri, Takuji (JGI)
In this paper, we have developed a novel approach to three-dimensional inversion and interpretation of multimodal geophysical data, which incorporates known geological/geophysical constraints. In a general case, the geophysical inverse problem is ill posed, i.e., it is non-unique and unstable. However, appropriate a priori information can help reduce the non-uniqueness and increase the stability of the ill-posed problem. The developed approach uses the principles of inversion “guided�? by known information. In the framework of this approach, the 3D inversion itself is data driven, but a priori geological/geophysical model is used as the initial and reference model during the iterative inversion process. We have applied the developed method to the integrated interpretation of magnetotelluric, gravity, and magnetic acquired in Yamagawa geothermal field of Japan, using constraints based on seismic and well-log data acquired in the same area. The results have demonstrated that the developed method produces reliable 3D models of different physical properties, which provides a solid basis for geological interpretation of the complex subsurface structures in the survey area, critical for geothermal exploration.
Presentation Date: Wednesday, October 17, 2018
Start Time: 8:30:00 AM
Location: 213A (Anaheim Convention Center)
Presentation Type: Oral
Zhao, L. Z. (Institute of Electrical Engineering Chinese Academy of Sciences, School of Engineering Science) | Chen, X. Q. (Institute of Electrical Engineering Chinese Academy of Sciences, School of Engineering Science) | Peng, A. W. (Institute of Electrical Engineering Chinese Academy of Sciences, School of Engineering Science) | Li, R. (Institute of Electrical Engineering Chinese Academy of Sciences) | Sha, C. W. (Institute of Electrical Engineering Chinese Academy of Sciences)
The electromagnetic separation method is a new way to treat oily waste-seawater from ships which is in a pattern of oil-seawater mixed flow. In this paper, the mathematical model and numerical scheme of oil-seawater mixed flow under a magnetic and an electric field were set up and verified again previous experimental results of Takeda. And the flow field and separation characteristics of an electromagnetic separation channel were investigated numerically. The simulation results show that: 1) the downward electromagnetic force causes the downward deflection of seawater and the floating of oil droplets via a form of buoyance, which results in the separation of the oil droplet and seawater; 2) the inlet velocity of the mixture vm, electromagnetic force density fe and diameter of the oil droplet d2 affect the separation rate of the oil droplet η and η decreases with vm and increases with d2, and there is a certain fe to get the maximal η when the opposite effects from the electromagnetic force and inertial force get balanced.
Oily waste-seawater from ships is one of the most common sources of offshore oil pollution. It includes oily ballast water’ oil tank washing water and bilge water which are produced in the process of normal operation. As to the oily waste-seawater from ships’ tiny oil droplets with diameters of 10∼100μm are suspended in seawater in the form of floating oil’ dispersed oil and emulsified oil. And the oil droplets and seawater are in a mixed flow pattern. Disposal of oily sewage from ships has always been an important part of the marine pollution prevention. The MEPC107(49) resolution adopted by the International Maritime Organization in 2003 stipulates that the oil content of all seawater drainage is not more than 15mg/L. Some countries and regions, such as Japan, put forward even more stringent requirement of less than 5mg/L. The traditional oil-seawater disposal technology and device can't meet the strict demand. So new disposal methods, such as cyclone separation (Huang et al., 2018), electromagnetic separation (Peng et al., 2007, Takeda et al., 2012’ Jiang et al., 2016), active carbon separation(Yi et al., 2018) and biofilm technology(Cappello et al., 2015) have been put forward and researched in the past few years.
In recent busy ports and harbors, their tranquility must be affected with not only storm waves propagated from outside but also harbor waves generated by inside ship navigation. In this study, a new generation method of ship waves is developed and installed to a Boussinesq-type wave transformation model, considering expandability of setting of ship navigation channels and applicability for general ship shape in a harbor. Through several sets of numerical simulations representing ship waves measured in model experiments, a tuning parameter related to the ratio of ship width and length to computational mesh size is introduced for each approximation function of ship shape.
On harbor tranquility analysis, a distribution of wave height inside a harbor is usually estimated with a numerical wave transformation model, considering wave diffraction around breakwaters and wave reflection on seawalls. Recently, many kinds of nonlinear wave transformation model, e.g. Boussinesq-type, have been employed to simulate wave field in shallow water. NOWT-PARI (NOnlinear Wave Transformation model by Port and Airport Research Institute) produced by Hirayama (2002), which has been already widely used to estimate harbor tranquility in Japan, is one of them. By dealing with several boundary conditions, it can reproduce the wave transformation in a harbor and a coastal area in random seas (Hirayama, 2013).
In recent busy ports and harbors, their tranquility must be affected with not only storm waves propagated from outside but also harbor waves generated by inside ship navigation. The ship waves are, however, not always focused on in coastal engineering except by a few researchers because their height and period are usually smaller than storm waves’ height and period. On the other hand, though the ship waves are studied in naval architecture in order to reduce one of sailing resistances (e.g. He et al., 2017), their propagation and transformation are rarely focused on.
Kim, Shinwoong (Nagoya University) | Nakamura, Tomoaki (Nagoya University) | Nehashi, Soraka (Nagoya University) | Nakayama, Ryoya (Nagoya University) | Cho, Yonghwan (Nagoya University) | Mizutani, Norimi (Nagoya University)
To determine the mechanism of gravel profile deformation, the change in the spatiotemporal beach profile is investigated by hydraulic experiments. The temporal profiles are obtained by image sampling, and the groundwater flow is analyzed by using dye. By utilizing these results, various experimental scenarios are investigated to reproduce ordinary morphological deformations such as berm formation, collapse, movement, and growth, under accretive wave conditions. As a result, it is observed that the wave interacts in a complicated manner with the downwash and profile, and that the change of the break-point bar, amount of moveable sediment, and bathymetry lead to variable morphological change.
Gravel beaches are primarily located in rough wave environments. The frequent occurrence of storm waves has the direct consequence of beach erosion and rapidly deforms the beach within a relatively short amount of time. Littoral drift, and infragravity and tidal waves, are also important factors contributing to beach erosion (Katoh and Yanagishima, 1992; Mizuguchi and Seki, 2015). However, the overall amount of external energy is predominant in wind waves and swells. This fact becomes more apparent when the target beach consists of gravel and is located in a particular environment, where it is subjected to microtidal or low mesotidal conditions. Consequently, the incident wave and sediment transport in the cross-shore direction are treated as the most influential factors affecting the occurrence of dynamic changes in the morphology of the beach, and determine the relationship between the wave information and the deformation of the profile, which is one of the main issues that has been investigated by previous studies (Dean, 1973; Sunamura and Horikawa, 1974; Hattori and Kawamata, 1980). These issues are still being introduced in the Coastal Engineering Manual (2008), and the Technical Standards and Commentaries for Port and Harbour Facilities in Japan (2009). Sunamura and Horikawa (1974) proposed the classification of the beach profile by using the wave height, wave period, slope of the initial profile, and size of the sediment grain. The use of this discriminant equation facilitates the categorization of the beach profile as an erosive or accretive type, under given wave and beach conditions. Hattori and Kawamata (1980) solved the problems in the application of grain size by utilizing the sediment’s fall velocity based on the balance of an external force acting on the sediment particle between the stirring power of the suspending sand and the resisting power of the fall velocity. Dean (1973) also mentioned the importance of the dimensionless fall-time parameter, which consists of the fall velocity, wave height, and wave period. However, these studies could not explain the process of morphological change and the variable of morphodynamic deformation, which occur on the beach face due to using the fragmented wave information and profile slope.
Matsumoto, Kazuyuki (Nippon Kaiji Kyokai) | Fukui, Tsutomu (Nippon Kaiji Kyokai) | Nanno, Shota (Nippon Kaiji Kyokai) | Aihar, Shuji (University of Tokyo) | Kawabata, Tomoya (University of Tokyo) | Shibanuma, Kazuki (University of Tokyo) | Inoue, Takehiro (Material Properties Evaluation Divsion) | Okawa, Teppei (Steel Research Laboratory) | Tagawa, Tetsuya (Steel Research Laboratory) | Tajika, Hisakazu (Steel Research Laboratory) | Imamura, Hiroki (Plate & Products Marketing & Technical Service Department)
On the background of increasing demand in ship transportation, capacity of container ship has been growing to achieve low cost shipping and ultra-large container ships of 20,000 TEU class have appeared in the recent decade. With the enlargement of the container ships, it was expected that the extremely thick steel plates with thickness exceeding 80mm are applied to the longitudinal strength members in the strength deck structures of container ship, such as hatch side coaming and upper deck, etc.
International Association of Classification Societies (IACS) released its Unified Requirements (UR) on brittle crack arrest design for the use of extremely thick steel plates in January 2013. This UR requires the application of brittle crack arrest steel plates with a brittle crack arrest toughness value (Kca value; material performance required to arrest a brittle crack) of 6,000 N/mm3/2 or more at −10 °C in case of the use of extremely thick steel plates. However, there are no specific rules for cases where the thickness of brittle crack arrest steel plates exceeds 80mm. Therefore, there is an urgent need to clarify required Kca value for extremely thick brittle crack arrest steel plates with thickness of more than 80 mm.
Against background above, Nippon Kaiji Kyokai (ClassNK) carried out the joint research project with in collaboration with Japan Welding Engineering Society (JWES). In this project, the verification tests were carried out by large/ultra-large scale structural model arrest test specimens simulating the actual construction of the hatch side coaming and upper deck with thickness of 100 mm for ultra-large container ships. Based on these verification test results, the required Kca value for brittle crack arrest steel plates with thickness of more than 80 mm and 100 mm or less was discussed.
As large open hatches are necessary for efficient cargo handling in container ships, hull girder stress must be ensured by a limited number of longitudinal strength members, such as the upper deck, hatch side coaming and sheer strake, as shown in Fig. 1.
This paper presents and evaluates a new reinforcement technique, based on the use of rubber sheets and Permex blocks to negate the effects of tsunami-induced instabilities (seepage flow and scouring) on a caisson type composite breakwater. In this study, a series of hydraulic model tests (on a 1/100 scale prototype) were performed and the effectiveness of the countermeasures was evaluated based on the displacement of the caisson, mapping the seepage flow pattern within the mound and calculating the stable weight of the mound. Results obtained from this study verified that the proposed countermeasures significantly improved the overall stability of the breakwater.
The 2011 earthquake off the Pacific coast of Tohoku (Mw=9.0 earthquake) resulted in the biggest and deadliest tsunami in the history of Japan. The tsunami reached a run-up height of 22 meters at the bay mouth of Kamaishi (Mori et al. 2011), while a GPS wave meter (18 km from the coast of Kamaishi) measured a 6.7 m high tsunami (Sugano et al. 2014). The Kamaishi breakwater, the world's deepest breakwater of that time, failed to stop the tsunami and was left heavily damaged.
Previously the breakwaters designed were more focused on being resilient towards wind waves and therefore the researches related to the behaviour of breakwaters during tsunami waves (especially those caused due to massive earthquakes) were fairly limited. All that changed after the 2011 Great East Japan Earthquake. And Kamaishi breakwater became a hot topic for researchers, especially in Japan. Arikawa et al. (2012) and Maruyama et al. (2014) separately conducted researches to determine the cause of the failure of caisson type composite breakwater and reached the common conclusion that the inadequate resistance against tsunami-induced instability problems (tsunami-induced seepage flow and overflow) played a major role in the failure of the breakwater. Takahashi et al. (2014) evaluated the stability of caisson type breakwater under tsunami-induced seepage flow by carrying out tests based on the centrifuge technique and performed FEM analysis (Finite Element) to conclude that the seepage force decreases the bearing capacity of the mound. This conclusion (of reduction of bearing capacity due to seepage flow) was also reached by Kasama et al. (2016) who also conducted a stability evaluation study of a composite breakwater under tsunami flow. He further noted that using a countermeasure model based on gabions is useful in reducing the likelihood of seepage failure, however the rubble filled gabion was not effective in improving the bearing capacity of the mound since its effective weight was not sufficient to contribute to the overall strength of the harbor side rubble mound. Hazarika et. al (2015) experimentally verified that the whirlpools generated by the overflow of the water during the tsunami caused a scouring of the harbor side rubble mound while the seepage flow in the region below the caisson resulted in settlements and displacements of the caisson.