Kansai International Airport was constructed in Osaka bay as the first offshore airport in the world. At the construction site, more than 20m of the soft holocene clay layer and hundreds of meters of the pleistcene clay layer deposited. There were many important geotechnical issues, such as the soil stabilization of holocene clay layer, and the prediction of consolidation settlement of pleistcene clay layer. To solve these problems, we have dealt with many investigations, such as a lot of deep boring surveys. This report shows the approach of the settlement prediction technique, and countermeasure against the settlement on the site.

View full abstract

   Case study using base friction model and DEM of Echizen rock fall disaster in Fukui prefecture in 1989 indicates that a risk analysis by disaster scenario and risk assessment matrix is useful decision-making tools for reduction of rock fall disasters which have many uncertainties in their occurrence and consequence. The matrix consists of both axes i.e. likelihood of event occurrence and impact of consequence, and normally the matrices should lead to decisions in three categories or priorities.
  In order to propose more probable scenarios we should prepare and apply useful data-base of rock fall disaster inventories.

View full abstract

  This paper describes the simulation method to explain the mechanism of the permeability characteristics of specimens with single discontinuties under shear through shear-flow coupling tests, showing that on the shear stress-displacement curve obtained by the constant normal load testing, the water flowing through the discontinuties have different transmissibility-aperture width relation before or after the yield range. As a technique to serve this purpose, the lattice gas automaton method, which is to substitute the fluid with particles and repeat letting them collide. With this technique, the factors of surface structure of discontinuties that determine the shear/permeability characteristics are identified.

View full abstract

  Most of old small earth dams for irrigation were mostly accumulated with the muddy soil in reservoir that caused the water pollution and the loss of reserved water. In order to make efficient use of the muddy soil as the embankment soil for rehabilitating old embankments, we have developed a new type method to rehabilitate the old small earth dam embankment by means of the cement-mixed muddy soil.
  We investigated several examples of the old small earth dams that improved the safety and prevented the leakage of the existing embankment by applying the new type rehabilitation technique. This paper presents a general consideration of the factors to be considered in designing to improve the safety and to prevent the leakage of an old embankment dam. We concluded that it is important for the design of zoning pattern to rehabilitate the old small earth dam to minimize the strength gap between the additional embankment constructed by the cement-mixed muddy soil and the existing embankment.

View full abstract

  This paper describes a study on efficient pre-excavation grouting concept using cement grout for reducing water-inflow during deep underground excavation in hard crystalline rock. Although thick grout mix is favorable for the efficiency, clogging phenomenon at the entrance of rock fractures in grout hole is a critical issue. The clogging phenomenon is therefore studied by laboratory experiments considering single and plural fractures. Although it is possible to increase grout volume by raising grout pressure for the case of single fracture, it is unreallistic to raise grout pressure for the case of plural fractures due to the concentrated flow into large fracture. Finally, the efficient pre-excavation grouting concept with moderate to thick grout mix is proposed based on laboratory studies.

View full abstract

  To produce the raw soil used to develop the foamed mixture lightweight soil, five kinds of decomposed granite soil with different degrees of weathering were used. The specified flow value can be satisfied when the soil cement ratio is 1 and the ignition loss is 4% or less. At the soil cement ratio of 3 or 5, where the specified flow value cannot be satisfied, adding a high range AE water reducing agent satisfies the value if the ignition loss is 5% or less. The unconfined compressive strength of the mixture decreases as the degree of weathering increases. Without addition of the high range AE water reducing agent, the target strength can be satisfied if the specified flow value is more or less satisfied. However, if the high range AE water reducing agent is added, the target strength cannot always be obtained even when the specified flow value is satisfied.

View full abstract

  Shake table tests of two large-scale models with liquefiable deposit on lateral spreading are performed to reveal the failure mechanism of sheet-pile quay wall and pile foundation. These tests simulate the lateral spreading behavior of the deposit with slow rate of ground deformation. The test results also indicate that deposit's residual deformation induced by cyclic motions and structure's inertial force influence largely the deformations of the pile foundation. In order to reproduce the lateral spreading phenomena observed in the large-scale shake table tests, centrifuge tests of small models are conducted. The centrifuge tests are effective in respect of prediction of the lateral spreading phenomenon.

View full abstract

  A computer program of rigid plastic finite element analyses considering soil anisotropy was developed for evaluating the lining pressures and the verification was successfully attempted by comparing the calculated results with existing theoretical predictions. A direct comparison was made for well documented field measurements of tunnel lining pressure and pore pressure together with comprehensive testing data of the soft clay. The results demonstrate that the rigid plastic finite element analysis is one of the effective methods for evaluating lining pressures of tunnel in soft clay.

View full abstract

   Because road embankments damaged by earthquakes have been increased recently, the proper seismic design and reinforcement of road embankments are necessary for future disaster prevention. New design concepts: control of sliding failure and smoothing of longitudinal road surface elevation and a new management concept for blocked road just after an earthquake are proposed considering the road performance required. The applications of these new concepts are discussed based on dynamic centrifuge tests, simple numerical methods proposed and vehicle running tests. Based on the above discussion, future views on the seismic performance-based design, reinforcement and traffic management of road embankment are proposed.

View full abstract

  During the construction of excavated shallow overburden tunnel on soft ground using NATM, a phenomenon occurred of equal settlements of the surface, crown and footing, called the phenomenon of accompanied settlement. Footing reinforcement piles was used to prevent the surface settlement. In this study, FEM analyses are carried out to clarify the reinforcement mechanism of the footing reinforcement pile installed obliquely. The results of the numerical studies indicate that obliquely installed piles are effective than those installed horizontally and can prevent surface settlement by increasing the shear reinforcement effect and load dispersion effect by axial force.

View full abstract

  Earthquke-induced residual displacement of rubble mound revetments, widely used in Kansai International Airport, have been studied in this paper. Because of the absence of preceding studies on the issue and nonexistence of earthquake-affected rubble mound revetments, it was difficult to evaluate the residual displacement accurately by numerical analysis alone. Therefore, the authors have been conducted a comprehensive consideration on the issue, which contained shaking table tests, in-situ microtremor measurements, liquefaction prediction on the fill materials, and numerical analyses. As a result, it was concluded that the rubble mound revetments would not be so much displaced by earthquake motion in Kansai International Airport.

View full abstract

  Clinker ash is the coal ash that is collected in the bottom water-tank of the boiler of a coal-fired power station, and it is crushed to the grain size level of sand and gravel. No special processing is required for using it and it is a light-weight material with high shear strength. Therefore, using the clinker ash as a ground material is now in progress. However, this has been carried out without a sufficient understanding of its characteristics. In this research, the particle characteristic of the clinker ash was thoroughly investigated. Assuming that the clinker ash is to be used as a soil-material for reclamation ground, its cyclic or monotonic shear strength and deformation characteristics were examined in loose condition. As a result, it was clarified that even though the clinker ash is a friability material, it has a high monotonic shear strength even in loose condition and that it has a high undrained cyclic shear strength when compared with the Toyoura sand or decomposed granite soil.

View full abstract

  The rock mass strength evaluation method combining a mathematical homogenization theory and critical strain of rock mass is proposed. This method is based on two basic ideas. One is that we extend critical strain expressed by axial strain on triaxial compression test to the expression by the second invariant of deviator strain on three dimensional strain field. And the other is that the macroscopic failure criterion is evaluated by calculating macroscopic stress corresponding to failure strain. Shear strength of the jointed rock mass was evaluated by this method, and compare with the examination. As a result, it was clarified that the macroscopic strength change in according to failure strain. A methodology to estimate for rock mass strength was devised by using the evaluation method.

View full abstract

  The last goal of this study is to develop a constructing method of the high density sand pile by irradiation of the ultrasonic wave that can reduce the noise, the vibration, the electric consumption widely. The purpose of this study is to examine the three points of following by comparing the test specimens made by irradiation of the ultrasonic wave with the test specimens made by the compaction method. (1) Uniformity. (2) Increasing tendency of the density. (3) Shearing characteristics. From the result of the experiments, it was confirmed that the examined three points of the test specimens made by irradiation of the ultrasonic wave were more than the same level as the test specimens made by the compaction method.

View full abstract

  The potential of surface ground-penetrating radar (GPR) for measuring unsaturated seepage flow in sandy soils was evaluated. It is shown from field infiltration experiments performed in homogeneous unsaturated dune sands. Non-steady behavior of the wetting front caused by two-dimensional seepage flow from the infiltration tests was non-destructive measured by using GPR in profile survey modes with the antennas on the surface. The utility of our proposed GPR profile survey was demonstrated by using seepage flow analysis of field infiltration experiments. There was good agreement between computed and measured wetted zone movements in two-dimensional unsaturated seepage flow.

View full abstract

  Disc cutter wear in TBM tunneling is caused by initial fragmentation of a solid rock face (the primary fragmentation) and fragmentation of residual rock pieces between a cutterhead and a face (the secondary fragmentation). The authers have studied the relationship between the rate of cutter wear caused by primary fragmentation and the modified F value, and analyzed the proportion of cutter wear caused by secondary fragmentation in four projects. It was concluded that there was a good correlation between the two indices, and that the secondary fragmentation invited the excessive cutter wear beyond the estimation in the two projects.

View full abstract

  This study forcus on the liquefied stabilized soil one of the cement treated soil. To begin with, in this study, the mechanical properties of liquefied stabilized soil which incureded surplus soil or surplus soi mixed coal ash were revealed. Next this study conducted to investigate the reuse of excavated liquefied stabilized soil under the assumption that the liquefied stabilized soil was excavated in order to do repair or maintenance. As a results the characteristics of excavated liquefied stabilized soil was depended on cement content. It was revealed that the excavated liquefied stabilized soil can be reused directly, need to some improvement. Futhermore it was revealed that when the excavated liquefied stabilized soil was applied to liquefied stabilization method again, it have equivalent to mechanical properties of the liquefied stabilized soil and satisfy the Japanese geo-environment standard.

View full abstract

  The objective of this study is to establish a method to evaluate the risk associated with the failure and damage based on the deformation of embanked structure such as a road embankmet etc. At first, a method is proposed to evaluate the fragility curve by considering the uncertainty of the seismic response and the soil properties simply. Two limit states are defined based on the deformation of a sliding block. This method is applied to evaluate the effect of the uncertainty of seismic action and the spatial distribution of soil strength on the fragility curve is made clear. It is obtained that the seismic action have a larger effect as the uncertainty and that the factors affected each fragility curves are different from each other.

View full abstract

  Mountain tunnels damaged in the 2007 Chuetsu-oki earthquake were localized around the Tochikubo anticline, 30km southwest of the epicenter, although the tunnels near the epicenter were not much damaged. To examine a behavior of deformation around the damaged tunnels, we analyzed SAR interferometry and mapped the surface displacements associated with the 2007 earthquake. The estimated surface displacements reveal uplift deformation at the Tochikubo anticline. We interpret that the damages to the mountain tunnels were caused by flexural-slip due to uplift of the Tochikubo anticline or amplification of ground vibration due to earthquake directivity.

View full abstract

  This study focused on compression failure and spalling of concrete which can be considered as limit states of plain concrete tunnel linings, and proposed a numerical simulation method considering the compression softening of concrete which can express above mentioned phenomena. From the simulation analyses on the loading tests of 1/5 scaled railway tunnel concrete lining and the reproduction analyses on seismic damages of actual mountain tunnels, it was confirmed that the crack and the compression failure of plain concrete can be properly expressed, and the seismic damages of the tunnel are reasonably reproduced by the proposed method.

View full abstract

  Mountain tunnels are generally thought to be less susceptible to seismic damage. However, tunnels often suffer seismic damages such as cracks and compression failure depending on the magnitude of the earthquake and the distance from the epicenter. Authors paid attention to the seismic damage of tunnels in poor geological conditions and performed model tests and numerical analyses to clarify the mechanism of seismic damage to tunnels as well as the aseismic performance of tunnel lining. It was revealed that actual earthquake damage was able to be reproduced by the model tests, in which loading conditions and structural defects were modeled. From the model tests and numerical analyses, it was found that the void above the lining have negative effects on the aseismic performance. The tunnel rigidity can be effectively increased by constructing the invert, resulting in the reduction of tunnel deformation, especially heaving at the invert. However, as the stress in the lining is also increased by the invert when large ground displacement is expected, another countermeasure is necessary to prevent the failures caused by the overstress of the lining.

View full abstract

  Mountain tunnels are generally thought to be less susceptible to seismic damage. However, tunnels often suffer seismic damages such as cracks and compression failure depending on the magnitude of the earthquake and the distance from the epicenter. The authors proposed fiber reinforced concrete and a buffer material of styrene foam as the seismic countermeasures for the lining of newly constructed mountain tunnel in poor geological conditions and assessed their applicability by model tests and numerical analyses including the invert as existing countermeasure. It was found that the inverts can reduce tunnel deformation and bottom-heaving, and fiber reinforced concrete can improve the ductility of lining, disperse the cracks of the lining and reduce the crack widths, and the buffer material placed between the lining and shotcrete can suppress the tunnel deformation and cracks.

View full abstract

  Application of Tunnel Boring Machine (TBM) for constructing road tunnel is considered as the rational and economical tunneling method because rapid excavation and reduction of support lead to cost reduction. However, the application is limited to small section such as pilot tunnel and evacuation tunnel. To widen the adoption, establishment of design method for support of TBM tunnel is essential.
  The load acting on the support by the excavation with TBM was analytically calculated on the basis of the measurement results in sites. The load was also evaluated by the case of collapse above the face in TBM tunnel. Consideration on load for support design by TBM excavation was achieved in this study.

View full abstract

  The compaction grouting method is used for soil foundations beneath existing structures as liquefaction countermeasures. It improves the ground by injecting mortar into the ground with high pressure. However, heaving, which affects the existing structures, may be caused in the grounds by the injection. A prediction method for the heaving is proposed using cavity expansion method and conventional design method. The proposed method is validated with the field data in actual executions of the compaction grouting method.

View full abstract