At the sheet maps of active faults in Japan, the active faults as certainty III which might not be active fault, are also described. If we want to plan several construction projects, the handling of the active faults of these certainty III is many problems. However, reporting that active faults of certainty III showed that it is not a "caution Quaternary fault" is seen so far. In project implementation, these days the risk communication has become important, it is necessary to properly handling of the active faults of certainty III. In this paper, we taken up as an example the active faults of certainty III that are listed in the "66 Toyohashi" at the sheet maps of active faults in Japan, it was carried out Quaternary fault survey. As a result, we shown that this active fault of certainty III has not displaced from the Late Pleistocene, because of identifying the terrace deposits including the decayed gravel bed. Therefore, this active faults is not a caution Quaternary fault, and general civil engineering structures are not broken/damaged by a displacement on the surface ground by fault activity. Through this result, we presented the idea of engineering evaluation of the caution Quaternary fault.
The earthquake with a maximum seismic intensity of 6 that struck Noto Peninsula on March 25, 2007, has caused extensive damage to the 27.0 km length between Tokuda Otsu IC and Anamizu IC on the Noto Satoyama Kaido Expressway (former Noto Toll Road). Large-scale collapse of embankment at 11 locations, difference in road surface level and cracks at 37 locations, and damage to bridge at 6 locations has occurred, and the expressway as the emergency transportation road was closed to traffic. The expressway was temporarily opened to traffic after one month by prompt action just after the earthquake emergency and has been fully restored after four months.In this paper, field investigation and analytical study on feature collapses of the damaged embankment structure and water level inside embankment were conducted. According to the results, it is shown that large-scale collapse of the embankment were mostly occurred on widening and slope of the embankment, which was caused by the groundwater level and geological formation near the embankment. A simple method for calculation of groundwater level inside embankment was proposed in this study. It is found that the estimation of groundwater level due to infiltration flow from transverse direction of embankment is important for evaluation the stability of embankment.
Because of sudden reduction of the stiffness and the strength of the ground due to liquefaction during the earthquake, severe damages of foundation structures may be caused. A new seismic retrofit method for foundations, utilizing sheet piles as reinforce members, had been proposed as a method having excellent workability and economy. The reinforcement effect against liquefaction of this construction method was examined by model tests; however the structural reinforcing mechanism has not been explained. In this study, model vibration experiments are performed firstly, to confirm the improvement performance mechanism. Then, applicability of the prediction analysis method, using the 2D beam-spring system generally used for the practical design, is confirmed. Because of sufficient reproducibility of the experiment phenomena calculated by proposed method, it is verified that the reinforcement effects can be evaluated by the current design technique.
A probabilistic risk evaluation method that enables us to take account of the spatial distribution derived from the path and the energy of rockfalls is proposed. In the method, the spatial distribution of number of passed rockfalls is obtained from simulated results of DEM by applying the Gaussian mixture model. In addition, spatial distribution of the exceedance probability for acceptable rockfall energy can be obtained. In order to validate the proposed method, the method was applied to risk evaluation of a real rockfall which occurred in Aichi prefecture in 2015. According to the results of the validation, it was found that the method can provide effective information for rockfall risk evaluation, and the method can also reduce required calculation cost of rockfall simulations.
In this paper, the coupled effects of strain-rate as well as depositional age on one-dimensional consolidation characteristics of marine clays in Kobe Bay area are in detail discussed, based on the results of consolidation tests performed in the laboratory with a mission to predict long-term settlement of Holocene and Pleistocene clay deposits. Prior to a series of constant-rate of strain (CRS) consolidation test, a high quality of the marine clay samples was manifested by comparing the elastic shear modulus of laboratory samples against the comparable modulus when measured in the field. In the CRS tests performed using the clay samples spanning over a wide range of sedimentation age, the yield stress increased as the strain-rate increased. Moreover, the strain-rate dependency was more significant for younger clay samples. The effect of depositional age on the over-consolidation ratio (OCR) was successfully quantified by introducing the rate dependent coefficient, α.
Saturated undrained cyclic triaxial tests were performed to validate liquefaction counter measure on relative density Dr:65%, Dr:65% cement grouted and Dr:90% well compacted Ninohe Shirasu soil, under confining pressure of 90-100kPa. Cement grouted and Dr:90% soil generated positive dilatancy and effective stress recovered to initial value due to negative pore water pressure. And each cement grouted soil and Dr:90% soil liquefaction resistance increased 2.5 times and 3.3 times greater than Dr:65% soil. By referencing cyclic tests results, soil-water coupled FEM-FDM code material parameter set could be decided, and each earthquake behavior of Dr:65% and Dr:90% Shirasu ground was verified. The behavior of well compacted Dr:90% ground was better performance than Dr:65% one .
In order to maintain a slope rationally, it would be necessary to elucidate the relation between a slope performance index and time. In this paper, parametric studies were carried out by means of slope models, focusing on the long-term deterioration of slopes, using such analytical methods as limit equilibrium slope stability analysis and elasto-plastic finite element analysis. The deterioration was incorporated into the analyses as chronological changes of shear strength, Young’s modulus, etc. From the results, the discussion was held on the relations between the safety factor, a performance index for slope stability, and displacements which develop at given locations of the slope surface during long-term deterioration. Also the following factors were discussed; 1) the degree of each parameter’s influence upon the safety factor and displacements at given locations, 2) at which locations displacement measurements should be taken, when computed displacements are regarded as the values obtained from field measurements. Finally, a rational maintenance method of a slope based on the stability performance was proposed although a relatively rough one.
A series of laboratory triaxial tests that simulated fill construction on peaty ground with vacuum consolidation method were performed to examine that optimizing the rate and starting time of the fill loading can control the lateral deformation of the ground. The test results for two different types of peat soils under vacuum pressure, axial stress loading, and both of them revealed the following characteristic deformation behaviors. The lateral strain resulting from the isotropic vacuum pressure loading was significantly smaller than the axial strain because of anisotropy induced by constitution of peat fibers. The lateral strain resulting from the combined loading of the vacuum pressure and axial stress loading is strongly affected by the starting time and, in particular, the rate of the axial stress loading, and therefore can be controlled widely by the loading rate from drawing to inside to swelling to outside. This suggests a possibility of fill loading without lateral deformation on peat ground.
In practice, geosynthetic laid beneath the foundation is a common reinforcement technique to increase the bearing capacity of foundation. In this study, the geosynthetic with both ends are fixed with the soil has been investigated in order that the bearing capacity is improved and at the same time the settlement can be reduced. For this purpose, 2D model tests under 1g condition and 3D centrifuge model tests have been carried out as well as the corresponding non-linear FEM analyses. In the 2D model tests, several depths of the reinforcement have been tested under both concentric and eccentric loads. According to the 2D model test and simulation, we found that the appropriate depth of the reinforcement is not too deep. The 3D centrifuge model test and simulation were also conducted in order to confirm the reinforcing effect under actual stress condition. The results under the 3D model test also revealed that the bearing capacity increased significantly when reinforcing the ground in the same length or a little larger than the width of the foundation with an appropriate depth. The numerical simulation has shown a similar result as found in the observations.
August 28, 2017 There had been a service stop from Aug 28‚ 2017‚ 1:50 to Aug 28‚ 2017‚ 10:08(JST) (Aug 27‚ 2017‚ 16:50 to Aug 28‚ 2017‚ 1:08(UTC)) . The service has been back to normal.We apologize for any inconvenience this may cause you.
July 31, 2017 Due to the end of the Yahoo!JAPAN OpenID service, My J-STAGE will end the support of the following sign-in services with OpenID on August 26, 2017: -Sign-in with Yahoo!JAPAN ID -Sign-in with livedoor ID * After that, please sign-in with My J-STAGE ID.
July 03, 2017 There had been a service stop from Jul 2‚ 2017‚ 8:06 to Jul 2‚ 2017‚ 19:12(JST) (Jul 1‚ 2017‚ 23:06 to Jul 2‚ 2017‚ 10:12(UTC)) . The service has been back to normal.We apologize for any inconvenience this may cause you.
May 18, 2016 We have released “J-STAGE BETA site”.
May 01, 2015 Please note the "spoofing mail" that pretends to be J-STAGE.