The 2011 off the Pacific coast of Tohoku Earthquake caused soil liquefaction over a wide area. In particular, severe soil liquefaction was reported in the northern parts of the reclaimed lands around Tokyo Bay, even though the seismic intensity in this area was only about 5 on the JMA scale with low acceleration. The authors surveyed the residual settlement in the Urayasu district and then conducted effective stress analyses of sites affected and not affected by liquefaction. The analyses results were compared with the acceleration waves monitored with K-NET Urayasu or ground settlements surveyed. They were based on the acceleration observed on the seismic bedrocks in earthquake engineering in some other districts adjacent to Urayasu. Much of the settlement was due to the long duration of the earthquake, with further settlement resulting from the aftershocks. The study shows that the effects of aftershocks need to be monitored. The simplified liquefaction prediction methods using the factor of safety, FL, also need improvement.
During the 2011 off the Pacific coast of Tohoku Earthquake, the earthquake early warning system operated by East Japan Railway Company controlled the Shinkansen trains through information from its seismic stations before large shakings hit the line. By analyzing the event history of the system recorded in its monitoring PCs, it was confirmed that the system first detected the seismic motion at 14:46:38.9 (JST) based on the data of the Kinkazan seismic station located closest to the epicenter, and issued the first control signal to trains between Shiroishi-Zaoh station and Kitakami station of the Tohoku Shinkansen line at 14:47:02.9 through the excess of acceleration threshold of the Kinkazan seismic station. The signal was issued 12-22 seconds earlier than the time SI value exceeding 18 cm/s along the line, which is the required value to stop trains based on company rules. After issuing the first control signal, other seismic stations began issuing signals through the excess of acceleration threshold almost sequentially according to certain delays caused by wave propagation from the hypocenter. Eventually, 27 trains (19 of them were running) along the line were safely controlled. In this paper, after summarizing the configuration of the earthquake early warning system of East Japan Railway Company and the warning logics adopted for the system, the system performance during the 2011 off the Pacific coast of Tohoku Earthquake is evaluated and discussed in detail.
The 2011 off the Pacific coast of Tohoku earthquake brought severe damage caused not only by the tsunami but also by the ground motions. The present manuscript summarizes the source mechanism/process and the characteristics of ground motions around eastern Japan during the earthquake. For the last two years after the earthquake, many researchers have devoted their efforts to analyzing and discussing the source and ground motions. New findings from some recent works are also cited. We, furthermore, introduce characteristics of ground motions at some typical damaged sites, where no records of ground motions were obtained during the main shock, using time histories of after shocks.
Seismic design technique for bridges has improved gradually based on various experiences of damage from past earthquakes worldwide. Lessons learned from past earthquakes have been reflected in not only the design specifications for newly-constructed bridges but also in the seismic retrofit strategies for existing bridges. The 2011 Great East Japan Earthquake occurred on March 11, 2011 and the catastrophic damage resulting from strong ground motions and the huge tsunami was experienced in the Tohoku and Kanto regions. Since the seismic retrofit project for bridges has been significantly promoted after the 1995 Kobe earthquake, this is the first experience for retrofitted bridges to be excited by a large earthquake. To examine the effectiveness of the seismic retrofit of bridges through the 2011 Great East Japan Earthquake experience, the seismic behavior of some retrofitted highway bridges is reported in this paper and the damage compared to the damage found in unretrofitted bridges.
On March 11, the 2011 off the Pacific Coast of Tohoku Earthquake occurred and the huge tsunami widely ravaged the coast, carrying sediments inland. Because the sandy layer deposited by the past tsunami is well known to be one of the effective indexes to know the occurrence of the great earthquake in the past, it is very important to investigate the sand sediments left by the above great earthquake. In this study, a field survey on the soil sediments was conducted at 33 sites of three cross-sections along the Sendai Plain in Miyagi Prefecture. Furthermore, 54 soil samples were dug at each site and grain-size distribution tests were conducted to study the characteristics of the soil sediments in detail. The results of the study show that the fundamental characteristics of the sediments in this tsunami can be described as “fining upward” and “landward fining”, and the relation between the thickness of sand sediments and the distance from the coastline at the Sendai Plain can be obtained from the other investigations.
In the 2011 Great East Japan Earthquake, many civil infrastructures were heavily damaged by the tsunami, but most structures designed with post-1990 code were not damaged by ground motion. However, unretrofitted road bridges designed with pre-1980 code were damaged and it should be noted that some bridges designed with post-1995 code were severely damaged. In this earthquake, cracks in elastomeric bearings were observed in a wide region in the east part of Japan, and rupture of elastomeric bearings occurred in some bridges. This paper summarizes the characteristics of damage to road bridges induced by ground motion, especially focusing on damage to the rubber bearings of bridges.
The 2011 Great East Japan Earthquake caused liquefaction in many places in the Tohoku and Kanto regions. Because of some areas' geomorphologic condition, liquefaction occurred in artificially reclaimed lands along Tokyo Bay and the Pacific Ocean, filled lands on former ponds and marshes, and sites of excavation to get iron sands or gravels which had been filled. The most serious damage occurred in Urayasu City, near Tokyo. About 85% of the Urayasu City area liquefied and wooden houses, roads and buried pipes were damaged. However, buildings and bridges supported by piles were not damaged even though the ground around them liquefied. In the Tohoku and Kanto regions, river dikes were damaged at about 2,100 sites, mainly because of the liquefaction of the foundation ground and/or embankments. Sewage pipes and manholes sustained two types of damage: i) lifting due to the liquefaction of replaced fill soils, and ii) the shear failure of manholes and disconnection of pipe joints due to the liquefaction of filled soils and the surrounding ground. Oil tank yards, harbor structures and a tailings dam were also damaged.
After the 11 March 2011 tsunami, post-tsunami reconstruction planning has started. In this article several key points and difficulties in the reconstruction plan are introduced based on the experiences of the author, who is part of the planning process. Before explaining the problems with the reconstruction plan, comprehensive planning problems in rural areas are introduced. These problems are population decline, a super-aging society, decline of city/town centre and land problems. Next, the goal of post-tsunami reconstruction is argued through the key concept of “building back better” to confirm the purpose of the reconstruction. Finally, based on the tsunami protection level and its background thought, a number of dilemmas are discussed. For example, the result of the reconstruction project of “moving to higher ground” means a separated city/town/village, yet a compact city/town/village concept is required in the population decline phase.
This paper reports the drafting process and current outline of the reconstruction plan for Otsuchi Town, Kamihei County, Iwate Prefecture, which suffered devastating tsunami damage caused by the Great East Japan Earthquake.
Many historic civil engineering structures in eastern Japan were severely damaged by the Tohoku Region Pacific Coast Earthquake and the resulting tsunami on March 11, 2011. The Japan Society of Civil Engineers' Committee on Historical Studies in Civil Engineering established a Special Subcommittee on the Tohoku Region Pacific Coast Earthquake, and in cooperation with the Agency for Cultural Affairs and other relevant organizations the Subcommittee conducted a survey on the situation of the damaged historic civil engineering structures. This study was conducted in two stages: the primary survey and secondary survey. In the primary survey, a survey of the existence or absence of damage was conducted on 250 historic civil engineering structures that had been designated as “Important Cultural Property (structure),” a “Registered Tangible Cultural Property (structure),” or a “Civil Engineering Heritage Recommended by the Japan Society of Civil Engineers.”In addition, based on the results of the primary survey, the top six in terms of priority of investigation were chosen from the affected historic civil engineering structures. In the secondary survey, a field survey as well as interviews with their administrators was carried out to determine their status. The results of those surveys provided an overall picture of the situation and the causes of the damage to the historic civil engineering structures affected by the Tohoku Earthquake. Along with collating the results of a series of activities and investigations by the Subcommittee, this paper presents the findings, based on those results, on the conservation of historic civil engineering structures in the event of a disaster.
In the traditional methodology of risk management, a widely accepted practice is to seek rational means to maneuver anticipated risks in a rational way while excluding uncertain events whose probabilities are sufficiently low. The extensive damage caused by the Great East Japan Earthquake revealed the ineffectiveness of existing views on risk management in the area of unforeseen risk. Based on the assumption that all planning and analysis activities are impossible without prior anticipation, this paper presents basic views on the philosophy of risk analysis and its ability to transcend the wall of cognition. In addition, based on the viewpoint of post-positivism, this paper examines the risk communication that occurs between experts and non-experts. It also recommends goals that risk analysis should strive for. Finally, it highlights practical issues that might occur in infrastructure planning and examines challenges inherent in infrastructure planning and management.
In this study, we analyzed the actual amount of gasoline transported into the Tohoku region during the first month after the Great East Japan Earthquake. We found that: (1) the amount of gasoline supplied in the Tohoku region during the first two weeks was only 1/3 of the normal demand; (2) the shortage of supply in the first two weeks led to a huge “back-log of demand”; (3) it took four weeks for the backlog to be cleared and the lost (suppressed) demand during the period was equivalent to the amount of normal demand for 7 days; (4) the gaps between gasoline supply and demand in the Pacific coast areas were huge, compared with those in the Japan sea coast areas, while the gap in each prefecture of the Tohoku region was gradually reduced over time in the following order: Akita, Aomori, Iwate, Yamagata, and finally, Miyagi prefecture.
On March 11, 2011, the Great East Japan Earthquake occurred, and people found it very difficult to return home. To be prepared for earthquakes in the future, we need to understand the commuting situation and examine the measures undertaken to deal with problems. However, results from the surveys that were previously conducted did not provide sufficient detail to deeply understand the behavior and the situation of commuters returning home. In this study, we analyzed the Twitter tweets that mentioned Roppongi Dori Avenue, Meguro Dori Avenue, and Komazawa Dori Avenue in Tokyo within 24 hours after the earthquake. We found that location information in tweets could be treated as trip data to determine changes in the local traffic volume and traveling speed. By analyzing tweets, we can provide traffic information to commuters after a disaster.
The effects of the rolling blackouts conducted after the 2011 Great East Japan Earthquake, on railway service in the Tokyo Metropolitan Area (TMA) were analyzed in terms of passengers' generalized traveling costs. We employed the hyperpath-based route assignment model proposed by Spiess and Florian (1989) to compute the costs. Applications to the TMA's rail network indicated that the effects of the rolling blackouts varied across the areas and days. In particular, passengers from inland areas would have had larger disadvantages while passengers from seaside areas would have received less impact.
This paper summarizes the detailed heavy vehicle traffic flow on expressways for three months from March 11, 2011 as a result of the Great East Japan Earthquake. Day-by-day traffic changes, compared with historical data, and analysis together with related statistics showed the following results: The Western route called Kan-etsudou experienced 20% increase in traffic caused by detour trip toward the disaster region Tohoku during the first week. From the fourth week until mid-July after the earthquake, the average traffic volume increased by 20% compared with 2010, and average trip length increased by 10%. One of the major reasons for this change was that ports in the Tokyo Bay area were used as alternative freight transport routes in place of damaged ports in Tohoku. The influence of the disaster to the Tokyo Metropolitan Expressway network was quite limited.
The Great East Japan Earthquake that occurred on March 11, 2011 caused disruptions to transportation network such as roads and railways. In general, transportation network disruptions make distribution of relief goods difficult and are considered to have negative impact on the economy of the stricken region owing to a decrease in transportation accessibility. Focusing on Iwate Prefecture, which experienced significant damage to its transportation network, this paper analyzes the distribution of goods, especially demand and supply of food items, for three weeks following the earthquake. Considering the relationship between transportation network disruptions and reconstructions, it develops a regional econometric model that can analyze the time-series impact of transportation network disruptions and reconstruction-related demand, etc. on the regional economy, and conducts simulation analyses. The results of the analyses indicate that upgrades to supply systems, including the opening of transport routes, are critical toward ensuring a sufficient supply of food, and the impact of transportation network disruptions in the long term on the gross regional product is as large as the impact of actual damage on production equipment, labor supply, etc. and reconstruction-related demand after the earthquake.
For most Japanese companies and organizations, the enormous damage from the Great East Japan Earthquake (GEJE) was greater than expected. In addition to the great tsunami and the earthquake motion, the lack of electricity, fuel and other supplies disturbed recovery efforts and activities for business continuity. This should be considered an important constraint factor of large earthquakes. The Japanese government and industries should utilize the lessons of the GEJE and execute effective countermeasures, considering the concern of other great earthquakes occurring in Japan in the near future. Of the countermeasures, improving the earthquake-resistance of buildings and facilities is the most basic approach. In addition, the spread of a BCP (Business Continuity Plan) and BCM (Business Continuity Management) to private and public organizations is also indispensable. Based on the lessons of the GEJE, BCM should more clearly include the standpoint of supply chain management, and emphasize “alternate strategy” more. The central and local governments are requested, in addition, to develop their own BCP and to prepare prerequisites for the BCM of private sectors, such as showing damage estimations in detail and improving related frameworks.
The Great East Japan Earthquake of March 11, 2011 resulted in not only 19, 000 deaths and missing persons, mainly in the Tohoku Region, but also the evacuation of more than 400, 000 people during the peak period. Although such disasters are very rare, creating robust civil engineering structures to prevent potential threats would be a diffcult task. On the other hand, even though information and communication technologies are just one of the means available, they have significant potential in terms of organically connecting support from people in a variety of capacities when an emergency arises. From this perspective, keywords such as “evacuation training,” “group relocation,” “real-time tsunami sensing,” and “soft disaster preventions” emerged as a result of this earthquake. I would like to describe how people utilize information and communication technologies as a mediating channel to secure their safety and security during earthquakes, whether autonomously or at other times through the protection provided by infrastructure facilities. In particular, the emergency mapping technology involving manual preparation as well as input from probe cars is introduced in Section 2 as a successful example of how information technology could serve as a mediating channel. Furthermore, in Section 3, I will describe the activities for the Open Government that did not necessarily function as a mediating channel but remain major issues for the future. In Section 4, the mobile phone technology is discussed in order to consider how mediating channels can be provided on a real-time basis, with consideration for the future.
During the initial stage of a disaster, aircraft operate intensively and simultaneously use several airports as bases, given their mandate to promptly perform their duties. Previously, disaster management faced challenges such as insufficient airport apron space, shortage of aircraft fuel, and inadequate information sharing among various involved organizations. During the Great East Japan Earthquake, aircraft— pri- marily civilian and government helicopters—used the Iwate Hanamaki Airport, Yamagata Airport, and Fukushima Airport as bases immediately after the disaster struck. These aircraft performed tasks such as information gathering, emergency rescue, and personnel and goods transport. For this study, we interviewed personnel in the organizations involved in operating these aircraft and airports during the disaster. Further, we considered the operational realities of disaster response activities at each airport to identify the lessons learned and challenges met. We present our findings and detail the role of an airport as a disaster management facility and the challenges faced by an airport during a disaster.
District continuity after large-scale disasters requires that the business continuity of local organizations such as administrative groups and companies within the community be considered first. However, only 27.6% of large companies and 12.6% of middle-sized companies have their own Business Continuity Plan (BCP). The revival of the local community and economy significantly depends on the early recovery of local infrastructures, such as electricity, gas, roads and railways. Immediately after a disaster occurs, the construction industry, which is familiar with the local conditions, can play a significant and highly expected role. Therefore, it can be said that a BCP for construction companies can contribute to achieving district continuity. This study suggests intensifying district continuity based on new knowledge acquired from the development of a system that supports making a BCP.
Before the occurrence of the 2011 Tohoku earthquake, a tsunami inundation forecast system and a GPS buoy were installed in Tohoku. The huge tsunami generated by the 2011 Tohoku earthquake was observed with the GPS buoy, and the data were used to revise the tsunami warning. However, the tsunami inundation forecast system was not able to help in the evacuation. The tsunami inundation forecast system was a system that displayed an inundation forecast map corresponding to the tsunami height observed in the GPS buoy in real-time. We thought that the damage would have been mitigated if the information from these systems were used for evacuation. Especially, the tsunami reached Sendai around 36 minutes after the tsunami was observed in the Kesennuma-oki GPS buoy. We thought that damage might have been mitigated if the information was conveyed during these 36 minutes. The 2011 Tohoku earthquake was generated in Tohoku where such a system was constructed. Therefore we thought that we must report the process of constructing these systems, the effects of the systems and the problems encountered.
In the application of multiple Carbon Fiber-Reinforced Plastic (CFRP) plates onto a structural steel member, stepping of the CFRP plate ends is often adopted to prevent debonding. This approach requires the nonuniform extension of CFRP plate lengths. In this study, to shorten the length of CFRP plates, a nonuniform overlapping arrangement of several CFRP plate ends was proposed and the theoretical conditions of arrangement were proposed. Additionally, the design for the stepped-end arrangement of CFRP plates under a uni-axial load was shown. It was confirmed with stress analysis that the stress in the steel plate was reduced to the design value by bonding the CFRP plate with the proposed stepped ends.
This study investigated the feasibility of bridge health monitoring (BHM) using a linear system parameter of a time series model identified from traffic-induced vibration data of bridges, which data were obtained through a moving-vehicle experiment on scaled model bridges. In order to detect possible anomalies in bridges, this study adopted a parameter from autoregressive (AR) coefficients. Consideration was given to diagnosis of the bridge condition from pattern changes of identified system parameters due to damage. The Mahalanobis-Taguchi system (MTS) was successfully applied to make decisions on the bridge health condition. Observations demonstrate the feasibility of structural diagnoses of bridges from the identified system parameter.
This paper presents a system for monitoring quasi-static displacements, named GWSN for “GPS wireless sensor network”. This system consists of the technologies of a low-cost L1 GPS (Global Positioning System) and wireless sensor network. The low-cost sensor node and cable-less system enable us to deploy sensors in dense numbers over a vast area. In general, displacement monitoring using GPS has a trade-off relationship between energy consumption and accuracy of estimation. Measuring continuous data and applying a trend analysis or Kalman filter outputs a highly accurate displacement estimation but also needs much energy dissipation. To solve the trade-off relationship, a data compression method and a static GPS positioning analysis method were developed and implemented in the system. In these methods, the assumption of quasi-static displacement was taken into account. A prototype system was developed and experiments were conducted in a quarry site and in an ideal condition using the developed prototype. The experimental results show that the prototype system works without serious system trouble in outdoor environments and has a great potential to measure displacements with sub-centimeter accuracy.
A review of the current status and progress of steel arch bridges in China and Japan, as well as an outline of the design vehicle load and design method against global buckling for such bridges, is presented in this paper. The existing steel arch bridges in China and Japan were analyzed in terms of year of completion, main span length, structure type, main arch rib form and construction method. It is shown that the steel arch bridge in China has developed rapidly since 2000, characterized by a long main span, while in Japan it has stepped into a fast-growing period since 1955, with medium and small bridges holding a great majority. As for the main span length, most of the bridges have a span from 100m to 250m in China, while majority of bridges are shorter than 150m in Japan. Over 80% of the bridges in China are through and half-through bridge types, and the arch ribs are hingeless structures. However, over 88% of bridges in Japan are deck and through bridge types, and a two-hinged structure was mostly adopted in through and half-through bridges. Single-hinged and three-hinged arches were seldom adopted in the two countries. The rise-to-span ratios of the arches in China and Japan are mainly in the range of 1:6-1:4 and 1:7-1:5, respectively. Most of the arches both in China and Japan use solid box ribs, and only a small fraction uses truss ribs, in which box sections are mostly adopted for the truss members. The cantilever method and scaffolding method are the two main construction methods used in China and Japan, although some other construction methods have also been developed.
Severe corrosion damage in steel bridges has been found in spite of bridge maintenance through anti-corrosion coating and painting. It is especially easy for severe corrosion damage to occur around the support of steel plate girder bridges. The shear strength of steel webs can be decreased by locally corroded panels in the steel plate girder bridge. In this study, shear strengths and post-buckling behaviors of the steel web with locally corroded panels were examined according to corrosion conditions. For this purpose, shear buckling behaviors of shear loading test specimens were identified and evaluated by nonlinear finite element (FE) analyses. Shear buckling strengths of the locally corroded web panels were quantitatively evaluated according to corrosion damage and boundary conditions. In addition, the simple shear strength estimation method was proposed for locally corroded web panels.
The instrumental seismic intensity of Japan Meteorological Agency (JMA) uses three types of filters which consist of high-cut, low-cut and period functions. An extended function of the low-cut filter is used to evaluate the effect of long-period range on seismic intensity in the paper. An asymptotic filter processing of acceleration in the extended function is proposed to express seismic intensities corresponding to velocity and displacement. The seismic intensity level using the running r.m.s. method is applied to clarify the effects of various frequency-weighted accelerations on seismic intensity. The seismic intensity levels corresponding to velocity and displacement are also discussed and compared with intensities of spectral characteristics.
A coupled fluid-structure-sediment interaction model is applied to a tsunami/storm-surge disaster mitigation structure attached with a movable crown to investigate the mechanisms of the movable crown behavior and wave energy dissipation. The model is composed of a large-eddy simulation solver for computing incompressible viscous air-water flow that considers the motion of a movable structure and the profile evolution of the seabed, a volume-of-fluid module for tracking air-water interface motion, an immersed-boundary module for computing movable structure motion, and a sediment transport module for computing suspended sediment motion and seabed profile evolution. The modules are connected to the solver using a two-way coupling procedure to ensure fluid-structure-sediment interaction. Numerical results show that the relation between the fluid inflow/outflow rate through a gap in the crown and the angle of the movable crown is an important parameter in predicting the wave field around the structure and the behavior of the movable crown. This suggests that it is essential to calibrate the parameter against the experimental data in numerically evaluating the performance of the structure for optimal design. It is also found that the motion of the movable crown is affected by the air trapped in the flood-control basin at the time of uprush and the air flow entering the flood-control basin at the time of backwash, suggesting that it is important to consider not only water flow but also air flow in the numerical simulation. Furthermore, the structure is found to efficiently dissipate wave energy due to vortices forming around the crown and the motion of the movable crown.
Data assimilation (DA) methods have received increased attention as a means to accomplish uncertainty assessment and enhancement of prediction capability in various areas. Despite their potential, applicable software frameworks for probabilistic approaches and DA are still limited because most hydrological modeling frameworks are based on a deterministic approach. This paper presents a hydrological modeling framework for DA, namely MPI-OHyMoS. While adapting object-oriented features of the original OHyMoS, MPI-OHyMoS allows users to build a probabilistic hydrological model with DA. In this software framework, sequential DA based on particle filtering (PF) is available for any hydrological models considering various sources of uncertainty originating from input forcing, parameters, and observations. Ensemble simulations are parallelized by the message passing interface (MPI), which can take advantage of high-performance computing (HPC) systems. Structure and implementation processes of DA via MPI-OHyMoS are illustrated using a simple lumped model. We apply this software framework to uncertainty assessment of a distributed hydrological model in both synthetic and real experiment cases. In the synthetic experiment, dual state-parameter updating results in a reasonable estimation of parameters converging into the synthetic true. In the real experiment, dual updating also shows good conformity with the observed hydrograph, having reduced the uncertainty ranges of parameters. Deterministic modeling, based on parameters estimated via PF, shows good performance for extreme events, while dual updating via PF shows improved performance for all events.
A free-surface velocity divergence is highlighted as a key parameter of the gas transfer, because accurate divergence value can be obtained with advances of the PIV technique. However there still remain uncertainties about relation between free-surface divergence and gas transfer velocity in open-channel flows such as natural rivers. In this study, we conducted a horizontal free-surface PIV in laboratory flume together with DO measurements. A new physical model of gas transfer parameterized by the free-surface velocity divergence is proposed and this validity is examined intensively by comparison with present measured data.
In 1869 the Meiji Government launched a policy of encouraging migration to Hokkaido and started reclamation of the Ishikari River Basin. In September 1898, when farmland reclamation had started to expand, the Ishikari River was hit by an unprecedented heavy flood that resulted in catastrophic damage and 112 fatalities. This disaster prompted surveys for flood control. Another flood occurred in 1904. Okazaki et al. made detailed investigations and observations on the 1904 flood of the Ishikari River. Based on these investigations, a flood control plan focusing on cutoff works was formulated, and those works were implemented for the half-century from 1910. This study reviews the effects of the 1904 flood, which served as the basis for the flood control plan, on the primeval Ishikari River Basin of the time, utilizing the results of investigations by Okazaki et al. We use two-dimensional flood flow numerical simulation to examine the effects of cutoff works. We also explain how the flood control plan affected the basin development.
The ability of a gas dissolving device to improve the DO condition of water is evaluated using the oxygen transfer rate. Usually the oxygen transfer rate is measured in mixing-type treatment, where air bubbles are released in the water tank. This method, however, has some disadvantages, such as that it cannot be used for compressed-type gas dissolving devices and that it requires the evaluation of the overall gas transfer coefficient. The present study proposes a convenient method of evaluating the oxygen transfer rate which is applicable to gas dissolving devices of both compressed and pressure-free types, applicable to water with an arbitrary DO concentration, and does not require the evaluation of the overall gas transfer coefficient. Evaluation of DO improvement is done using the equivalent DO increment, devised to eliminate the influence of the DO concentration of the water before treatment. The value of the oxygen transfer rate is represented as the value at a temperature of 20 degrees Celsius. Laboratory experiments to check the method have shown that the proposed method of measurement is valid.
The purpose of this study is to determine wave group evolution by investigating the transformation of multi-directional spectra at constant depth and on a sloping beach. The transformation of wave groups can be evaluated by computing multi-directional nonlinear waves based on the third-order Zakharov equation. Initial conditions for numerical simulation were characterized by the Gaussian spectrum for several values of significant wave heights and water depths. The numerical results show that the distribution of the energy processes affects the evolution of the wave groups, and the characteristics of directional wave groups can be reproduced through the Zakharov equation model. Finally, field observation data at Akabane beach were used to demonstrate the transformation of wave groups in a real directional sea.
This paper describes the self-purifying function in term of water quality of a tidal flat in the Tokyo Port Wild Bird Park (TWBP). In this study, the authors carried out field observations of water quality over 2 tidal cycles and estimated nutrient fluxes between a tidal flat and the adjacent sea in the summers of 2006, 2007, and 2008. Sampling of benthos and bottom sediments and counting of water birds were carried out in the field. From the study, the authors found following the results: (1) This flat functions as a net sink of nitrogen and chlorophyll-a and a net source of phosphorus in summer. (2) Nutrient fluxes between sediments and the overlying water are large in proportion to the tidal flat area. (3) The amount of TN and TP removal by water birds is not very large compared to TN and TP fluxes between the tidal flat and the adjacent sea.
A three-dimensional hydrodynamic model for simulating estuarine dynamics has been developed. The model, called CIP-Soroban flow solver, has been specifically designed for reproducing the current and salinity fields in density-stratified water bodies with a free surface. It is based on the Constrained Interpolation Profile (CIP) scheme and the Soroban computational grid system. Simulations of the time-dependent current and salinity fields of the Tone River Estuary have been performed using this model. Two periods are used to examine the predictive capability of the model. The first was in August 1997, which produced extensive field data related to vertical profiles of salinity, which showed evident changes in salinity intrusion processes between spring and neap tides; and the second in August 2001, which produced sufficient data associated with continuous measurements of vertical profiles of velocity, which showed characteristic residual flows averaged over ten tidal cycles. The model is examined in detail to reveal its inherent capability of simulating the dynamic behavior of density flow in the Tone River Estuary. In these two periods, the measured salinity and velocity data are reproduced well by the 3-D model. After investigating the capability of the hydrodynamic model, the dissolved oxygen (DO) transport model is incorporated into the hydrodynamic model to study the role of density stratification and residence time of seawater at the onset and development of hypoxia. The results of a long-term simulation of 100 days show good agreement with the field data.
Spatial and temporal distribution of water vapor is important because local severe rainfall is caused by the convergence of water vapor. On the basis of field measurements in the Matsuyama Plain, we found that urban absolute humidity was lower than rural absolute humidity. Following the manner of urban heat island phenomenon, we call this phenomenon “urban dry island” (UDI). The object of this study was to analyze the features and causes of the UDI. The UDI phenomenon was significantly found at daytime during fine days due to the difference in water vapor fluxes at urban and rural sites. The UDI was most prominent in the morning and in the late afternoon, in time zones where the sea breeze and land breeze altered each other and the wind speed temporally became low. Strong sea breeze transported humid air from the coastal regions to the center of the city and then caused the UDI to diminish. The UDI intensity was large in summer and small in winter. This was attributed to the small latent heat fluxes in winter and strong north-westerly monsoon, which enhanced the mixing of humidity. In addition, we investigated the impact of UDI on the formation of clouds using datasets of cloud base level, which was obtained by a ceilometer in summer. Cloud base level over urban areas tended to be higher than that over rural areas under the condition that the wind blew along the border between urban and rural areas. This was demonstrated by lifted condensation level, which was estimated from surface air temperature and water vapor content.
The use of the Rehbock formula for measuring flow rates with full-width sharp-crested weirs, specified in ISO 1438, is restricted to weirs with a weir plate height of less than 1 m. Previous studies have shown that deviations in measured discharge coefficient from the Rehbock coefficient increase with increasing weir height at heights of over 1 m, owing to the scale effect of weir height. In this paper, a new discharge coefficient is proposed for use when applying the Rehbock formula to weir plate heights over 1 m, as discharge flow rates of large-size pumps are usually measured using full-width weirs with a plate height as high as 2 m. Its validity is examined and verified, based on test results in studies by Schoder-Turner and later researchers. The paper also discusses the effect of scale on discharge coefficient in relation to the boundary layer on the weir plate.
On March 11, 2011, a very big earthquake occurred in the Tohoku district in Japan. As a result, a large amount of tsunami sludge was generated and radiation contamination due to the nuclear power plant disaster also became a serious problem. To ensure the safety of living environments, it became necessary to decontaminate the radiation-contaminated waste and soil, and for the radioactive pollutant to be stored at temporary storehouses. However, because ordinary cover soil or sheets deteriorate under rainfall or ultraviolet light, further improvement of this system was required. This study focused on the “Fiber-cement-stabilized soil method”. This method is a new recycling method for high water content mud such as construction sludge by using paper debris and cement. Thus, if the cover soil for radiation-contaminated soil could be produced from the tsunami sludge, we could make effective use of the tsunami sludge and store the radiation-contaminated soil securely. The cover soil requires high failure strength, high durability for drying and wetting, high durability for erosion by rainfall and low permeability. To evaluate the durability of the cover soil made of tsunami sludge against erosion by rainfall, the indoor artificial rainfall test and the outdoor test under natural rainfall were carried out. As a result, it was confirmed that the durability of Fiber-cement-stabilized soil against erosion by rainfall was very high.
This technical report presents a comparative study of the predictability of estimating the ultimate pile capacity between widely accepted international design codes of pile foundations, including the: Japan Road Association code (JPA, 2002), DIN 4014 (1990), Egyptian geotechnical design code-Part 4 (2001), and AASHTO (2007). The ultimate pile capacities inferred from the results of load-settlement test using the Chin extrapolation method (1970) were compared with the predicted values obtained from international codes of design. The study covers a wide range of Egyptian soil formations by utilizing 58 case studies of bored piles (loading tests) constructed and tested in numerous regions inside Egypt. The average error percentage obtained from each code of design has been calculated, and the predictability of these design codes has been evaluated based on four independent statistical criteria. JRA code (2002) and DIN 4014 (1990) have revealed well predictability and accuracy of estimating ultimate pile capacity against the other international codes of design.
This study was conducted to propose a simulation model for corrosion cracking of cover concrete in reinforced concrete structures located on land and subjected to airborne chloride. Chloride penetration has been known to have great influences on the design corroded mass due to the fact that it changes the corrosion initiating time and corrosion rate. Accordingly, a chloride penetration model was proposed for reinforced concrete structures located on land. This model was verified with the drawn core of concrete specimens taken from structures that were free from the rain washout effect. In this study, the corrosion rate of reinforcing steel was also proposed by considering the change in degree of saturation in concrete due to environmental conditions. With the changes in the degree of saturation, the effective corrosion rate is changed according to three controlling factors: the conductivity of the concrete, the chloride concentration and the supply flux of oxygen. Therefore, the design corroded mass is the integration of the effective corrosion rate from the corrosion initiating time to the design time. Moreover, a numerical formula for limit corroded mass, which causes cracks in cover concrete, was developed and proposed. The accuracy of the formula was approximately 25% as compared to the experimental results of previous studies. Thus, the cracking time is the time when the design corroded mass is greater than the limit corroded mass. Additionally, the simulations at the time of cracking in cover concrete were compared with three actual reinforced concrete bridges subjected to airborne chloride.
This paper presents an investigation of the shear carried by fibers of fiber reinforced concrete (FRC) beams consisting of various types and combinations of fibers, and a proposal of the predictive equation for their shear capacity. Eight FRC beams with stirrups were tested by four-point bending. The testing program employed five fiber types (30-mm steel, 60-mm steel, polypropylene, polyvinyl alcohol and polyethylene terephthalate) and three combinations of hybrid fibers. The stress transferred across a diagonal crack was investigated using crack surface displacement and tension softening curve. The stress was significantly affected by the material types and combinations of fibers. The stress and the angle of the diagonal crack increased with the increase in fracture energy, whereas the diagonal crack length decreased. On the other hand, the angle of principal tensile strain did not significantly vary in the range of study. The shear carried by fibers was investigated from the stress and area of the crack surface. Good correlation between test results and calculated results was observed. In addition, a simplified equation of shear carried by fibers, involving fracture energy, stirrup ratio and effective depth, was formulated. Finally, a predictive equation for shear capacity of FRC beams was proposed and validated with 43 FRC beams. The proposed equation gave good prediction for FRC beams with various types and combinations of fibers.
To promote more widespread use of high-strength concrete (HSC) for the efficient design of reinforced concrete (RC) beams, an experimental investigation on the effect of wide stirrup spacing on the diagonal compressive capacity of HSC beams was performed. The predictive equation for the diagonal compressive capacity of RC beams proposed by the authors was modified to cover the application to RC beams with wide stirrup spacing. Four 590-mm deep I-beams with wide stirrup spacing were tested by three-point bending. The influence of stirrup spacing, stirrup diameter, and the number of stirrup legs was discussed. The results show that the diagonal compressive capac ity linearly decreased with wider stirrup spacing regardless of its diameters when stirrup spacing was narrower than 140 mm; however, the effect of spacing became negligible when stirrup spacing was wider than 140 mm. Even when wide stirrup spacing was used, the diagonal compressive stress did not concentrate on the local area of the specimens and a sufficient confinement effect was achieved by providing two-legged stirrups; the localization of compressive stress on the struts was likewise prevented. Finally, the predictive equation by the authors was modified on the basis of the experimental findings. The modified equation covers the application to RC beams with wide stirrup spacing while maintaining adequate simplicity and precise prediction of the diagonal compressive capacity of RC beams.
This paper presents a strength model for Portland cement mortar with and without partial replacement mineral powders, limestone filler, blast furnace slag, and fly ash. The model was developed based on hydration heats and microstructure developments. The investigation was conducted on cylindrical mortar specimens with different water-to-cement ratios, different types of cements, and different curing conditions. The compressive strength of mortar was found to have a linear relationship with the ratio of hydration heat coupled with the porosity. Consequently, a strength model for mortar compressive strength, which is a summation of all heat-pore components multiplied by their own strength contribution factors, was established. The calculations of compressive strength using the proposed model agreed well with the experimental results in terms of cement paste, mortar, and concrete.
This study proposes a methodology to find the optimal inspection policy for road pavement with uncertain deterioration processes. Since the deterioration progresses are characterized by a lot of uncertainty, the pavement conditions cannot be deterministically evaluated unless the inspection or repair activities are carried out. The road administrators have to decide whether repair should be implemented based upon the results of inspection. In this paper, the value of the inspection is evaluated by using the real option theory, and the optimal inspection and repair model is formulated to investigate the optimal inspection frequencies and repair policy, which may minimize the expected life cycle costs. Finally, the validity of the methodology presented in the paper is investigated by a case study dealing with the expressway in the real world.
A new technology has been developed to establish a more reliable excavation control protocol than currently used to ensure face stability. The new technology comprises the development of a measuring device, such as flappers, for muck flow inside the chamber and numerical analysis to evaluate the status of plastic muck flow for earth pressure balance shield tunneling. Flappers were installed in the chamber of the shield machine and the torque on the flappers was measured. Then, a numerical analysis was conducted to satisfy the data obtained in the field. Once the numerical analysis had been obtained, the condition of the muck flow in the chamber could be evaluated. The result of the field application verified that this technology was useful to evaluate the status of and to control the muck flow inside the chamber.
This is a study on the development of a practical road disaster management system for various natural disasters by applying risk management techniques. Risk is defined here as the product of the likelihood of disastrous event and its consequences. The road facilities targeted are bridges, embankments, tunnels, slopes, and so forth. Various natural disasters such as earthquakes, tsunamis and heavy rainfalls are included in the analysis. Both direct and indirect damages are assumed in the present study. The former includes human damage and the restoration cost of damaged facilities, while the latter includes economic loss associated with traffic detouring. Particular emphasis is put on rating the risks to various road facilities due to different natural disasters by using a common index. Based on the proposed system, a case study was performed on a 110-km section of a national highway running along the Pacific coastline of Japan. This section of the highway comprises various kinds of road facilities, and the area where the highway passes through has high seismicity and has suffered from typhoons and resultant slope disasters. The results of the case study are presented through a risk curve, risk register table, and risk treatment plan, which are readily applicable to road disaster management.
In recent years, the cleanup of oil-contaminated sites by bioremediation has attracted much attention. In order to perform an effective bioremediation, suitable oil-degrading microorganisms should be induced in the remediation site with the accompanying nutrients. In this study, we investigated the bioremediation effects of 4 interventions-compost derived from food waste (food-waste compost), chemical nutrients, mushroom, and biofertilizer-versus no intervention (control) in a bioremediation field trial of oil-contaminated soil. Whereas the concentration of total petroleum hydrocarbons (TPH) in the control section remained largely unchanged throughout the experiment, large reductions in TPH concentrations were seen with all interventions. In particular, compost greatly decreased TPH concentrations, from 8,300 ppm to 2,300 ppm after 74 days. Furthermore, we obtained an understanding of the behavior of oil-degrading bacteria by quantifying the alkane monooxygenase genes (alkB and alkM), the catechol 1,2-dioxygenase gene (C12O gene), and the catechol 2,3-dioxygenase gene (C23O gene). We observed a tendency for oil-degrading bacteria to increase proportionally in the sections in which THP degradation was observed. In particular, compost was more effective than the other interventions in inducing the growth of bacteria possessing the alkM and C23O gene, resulting in a significant reduction in the concentration of alkanes and aromatics. Thus, we demonstrated that the application of food-waste compost to bioremediation was very effective. This technique can simultaneously solve the 2 environmental problems of petroleum pollution and the increase in food waste.