To carry out a 2D simulation of soft ground improved by vertical drains under embankment combined with vacuum preloading, a method to convert the axisymmetric consolidation of the drain to plane-strain consolidation is needed. The paper presents and verifies a proposed conversion method for a sandwich subsoil, where a sand layer is sandwiched between two clay layers, which is often found in many areas in Japan. The analyzed results showed that the proposed method produced very good matching results, not only for the drain having no-well resistance, but also for the drain having high well resistance in the subsoil.

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In this paper, we focus our attention on relationship between water behavior in soil and variation of ground temperature due to rainfall and solar radiation. A new method was proposed to evaluate the water behavior in unsaturated soil based on the ground temperature measurement results. The modeling test for seepage behavior was also conducted to validate the proposed model. Results obtained from this paper show that using this approach, a new relationship that described the status of “Heat-Soil moisture characteristic curve” can be found. By using the developed technique, the time and the value when pore-water pressure was increased greatly was in good agreement with experiment.

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To evaluate ground displacement reasonably, we propose an analyzing method of ground behavior by the principal component analysis. About the laboratory compression test with clear deformation behavior, we compared specimen deformation under compression with the calculated deformation mode by principal component analysis. As a result, it was shown that this method can divide the total displacement of specimen between the barrel type deformation and shear deformation. We applied this method to displacement data measured by the electro-optical distance meters on an excavation slope. As results, the following two points of the movement of the slope were clarified. After the slope moves in the direction of the valley in the early winter, it returns in the direction of the mountain The movement is larger than the cut slope in natural ground. Next, this method was applied to the displacement data measured by the electro-optical distance meters and borehole inclinometer in the slope near an existing hydroelectric power plant, and three-dimensional slope behavior was examined. It was clarified that the movement of the slope in the direction of the valley accounted for 70 percent of the total movement. This method has possibilities as the estimation on behavior of slope.

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A new bridge foundation named “Sheet-Pile Foundation” has been proposed based on our studies. Sheet-pile which is usually used as temporary member in an excavation work is being recognized to be used as permanent structure of high bearing capacity by connecting it to the footing. This paper reports two cases of full-scale loading test of a sheet-pile foundation. The result of these test show the high bearing capacity of Shet-Pile Foundation.

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A high-level radioactive waste disposal facility might be built in a coastal area in Japan from the viewpoint of feasible transportation of waste. Therefore, it is important to investigate the effects of seawater on a bentonite-based buffer. This study investigated the influence of seawater on self-sealing ability of three common sodium-types of bentonite by the laboratory experiment and chemical analysis. From the results of laboratory experiment, suitable specifications were defined for a bentonite-based buffer that can withstand the effects of seawater. Furthermore, mechanism on filtration of seawater components in highly compacted bentonite was discussed by the results of chemical analysis.

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Rainfall would reduce the seismic resistance of an embankment if the drainage system of the embankment is not enough; however, aseismic design of embankments does not consider this effect. Based on the seismic response calculation results using a FEM code ‘FLIP’ and the previous shaking table test results, the effect of rainfall on seismic performance of embankments was examined in this study. As a conclusion, the reduction of the soil cohesion of embankment by the seepage due to rainfall is very important.

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One of the most important parts that determine the safety of a waste disposal site is the imperviouslayer. Recently, fail-safe impervious layer consisted of bentonite-soil mixture has been widly used. Thepermeability performance of an impervious layer should be evaluated by using its coefficient of permeability. However, it has become a common practice in-situly that dencity or water content, characterisitics indirectly correlated to the coefficient of permeability, is used to evaluate the coefficient of permeability performance rather than the coefficient itself. To accurately assess the safety of a waste disposal site, it is considered that the coeffisient of permeability is directly used to control the quality. Due to this reason, a simple field test apparatus was developed. A direct measurement technique for the coefficient of permeability by using this test apparatus is discussed in this paper.

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A laboratory investigation was carried out into anisotropy and time effects on undrained shear behavior of Holocene clay underneath Kobe Airport. A series of undrained compression/extension tests as well as constant-volume direct shear box test both performed using different consolidation time and various shear rates was carried out. The ratio of undrained shear strength to vertical consolidation pressure, S_u/σ_vc was larger in the order of triaxial compression, direct shear box and triaxial extension tests. The S_u/σ_vc value also increased with the consolidation time and with the shear rate. The deformation and strength behavior exhibited an isotach property in which the shear rate was the predominant factor to govern the behavior.

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The distribution of the change in groundwater volume at the site of Mizunami Underground Research Laboratory in the Tono area, Japan, was estimated by the inverse method proposed by the authors, using tilt data measured with four tiltmeters at the surface during drainage, submergence and re-drainage in excavation of shafts. Furthermore, the reliability of the results was evaluated by a model analysis for groundwater flow in a single ellipsoidal field. The results showed that the hydrogeological structure for the region of 1000m×1000m in area and 100m to 180m in depth is such that groundwater flow occurs mainly in a region between two impermeable faults with the center at 100m to 150m south of the Main shaft and this region tends to shrink toward north-west and be widened toward south to south-east. However, at the same time, the model analysis showed that areas north-west and south-east of the Main shaft in the corners of the region are vacua for estimation due to the aligned layout of the tiltmeters.

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  After completion of a tunnel, constructed in soft rock, some deformations and cracks were observed on the lining. This situation was dealt with experimental judgment based on similar situations in the past. In view of recent tunnel repairing, the authors proceeded with investigating the quantification of prediction and reinforcement to repair the tunnel based on monitoring the deformation progress. In this paper, long-term measured tunnel deformations were simulated by ground strength reduction model. In addition, in order to evaluate the effects of various countermeasures for deformation, the proposed model is studied to examine their applicability to actual countermeasures and remaining issues. And, the characteristic of ground strength reduction is analyzed through the analysis of the deformed tunnel, and prediction method of deformation is proposed.

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  When evaluating trajectory of rock blocks in the event of bedrock slope failure, there is an usefull technique called three dimentional distinct element method which models shape and size of rock blocks faithfully. However, jumping height observed in a rock fall model experiment differs considerably depending on how a rock block makes contact with slope surface. This paper covers a rational dynamics model of the contact mechanism taking into account relations between coefficient of restitution and contact area in order to reproduce jumping of a rock block. We applied this idea to the rock fall model experiment and a real field and were able to get a good reproduction result.

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  As part of the construction of a new subway line in Osaka, Japan, called the Nakanoshima Line, a large and deep excavation has been successfully carried out by the open-cut excavation method with two earth retaining walls through the thick Holocene Nakanoshima clay deposit. In the present study, a case history of the excavation is numerically back analyzed via a viscoplastic finite element method. A comparison between the simulation results and the measurements shows that the simulation method can efficiently reproduce the deformation of earth retaining walls. In particular, the modified measured deformation of the earth-retaining wall by the measured axial force of the struts is consistent with the simulated results.

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  The conventional selection of construction method is focused on construction cost with the allowable safety factor. However, a performance of structure should be evaluated with an adequate method. In this study, to evaluate the performance of earth slopes with and without reinforcement, a life cycle cost was calculated on the seismic condition after the evaluation of damage cost functioned by a seismic deformation. For the calculation of the life cycle cost, construction costs were estimated from the actual construction data. In the results, the life cycle cost of the earth slopes with reinforcement was lower than that of the earth slopes without reinforcement.

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In order to use a ceramic industrial by-product “Kira” as a geomaterial, KIRA is improved by crushing, lime-mixing and compaction and its mechanical properties are investigated through laboratory tests and numerical simulations. The new findings as follows; 1) The unimproved soil is the soil in which the loss of overconsolidation proceeds as fast as the decay in structure with plastic deformation. 2) The 28-day strength is about 5 times as larger as the 0-day strength and the compressibility with 28 days curing is half of the one with 0 day. 3) A mixing “Kira” with lime makes speed of decay of soil structure and loss of overconsolidation decrease, and a curing makes initial structure high and initial overconsolidation heavy.

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  This study carried out full-scale tension, compression and shearing test for various types of joint sections in steel pipe sheet pile (SPSP) as detailed understanding of mechanical characteristics for the SPSP foundations. Furthermore, 3D-frame structural analysis that can consider obtained mechanical characteristics of joint sections in SPSP was developed.
  In this study, the tension, compression and shearing behaviors were clarified experimentally for P-P, P-T, L-T and H-H joint sections. Furthermore, applicability and validity of 3D-frame structural analysis with considering the mechanical characteristics of the joint section was confirmed.

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  To allevate the poverty in rural area of developing countries, maintenance of the small scale infrastructure is necessary. The communities are required to develop capacity for improving rural infrastructure on their own initiatives to mitigate the losses which are likely to occur in both production and transportation processes. To enable the people maintain the infrastructures by themselves, a simple maintenance method with Do-nou, which is a Japanese term for soilbag, was developed. The technical transfers of the developed method has been conducted in four contries in four different approaches. The objectives of the technical transfers are how to take the technology to the grass root and expand it in short period. Through the four approaches for the technical transfers some communities have started maintenance at their own initiatives. After the demonstration of the road maintenance, a community maintained a bridge by themselves using Do-nou. To maintain the rural infrastructures in developing countries leading to poverty alleviation, one approach from the department of civil engineering has been proposed.

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  A new evaluation method of a risk of slope failure during rainfall is proposed in this paper. In the new evaluation method, Principal component analysis (PCA) is employed, and the field measurement data (rainfall, pore-water pressure, ground displacement) are used as input parameter. Then, the effectiveness of proposing “principal component score (PCS)” as an evaluation index is investigated. As a result, PCS can be directly reflected rainfall intensity, water behavior in soil and ground displacement; and therefore it can be configured more concrete timing of dictating to evacuate and to release. Moreover, the soil tank test was also conducted, it was shown that the proposed method was the effective evaluation one.

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  In-situ air permeability (K_{a, insitu}) is a rapid field measurement that provides important information on soil-gas and water transport properties in soil. The K_{a, insitu} can be determined by using a shape factor taking account of field flow geometry effects on one-dimensional air flow. In this study, effects of lateral and bottom boundary conditions on the shape factor (G) and subsequent K_{a, insitu} were investigated by combining finite-element numerical simulations and a model experiment with repacked sand in a container. Results showed that calculated and measured values of G and K_{a, insitu} were highly dependent on the bottom boundary, and especially that a shallow zero-flux bottom boundary caused an underestimation of K_{a, insitu}. This shows that special care must be taken to determine the shape factor with due consideration to the proper boundary conditions. This is especially critical in the case of impermeable layers such as highly-compacted subsurface soil or a shallow groundwater table.

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The ground strength parameters (cohesion c and internal friction angle φ) are key factors in the seismic performance assessment of geotechnical works. However, the procedure to determinate the ground strength parameter is dependent on the experience of the engineers, and it is not well documented. In this study, a questionnaire survey to 76 civil engineers in Japan is conducted to reveal their empirical procedure of parameter determination. The result of the questionnaire clarify the considerable variation of determined ground strength parameters which depending on the experience of engineers.

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In this study, in order to clarify the effect of lime soil stabilization of acid sulfate soil, two kinds of soil samples (acid sulfate soil generated gypsum, and Fukakusa standard soil) mixed with calcium hydroxide at different mixture rate were investigated by pH tests, unconfined compression tests and scanning electron microscope observations. The following main conclusions are obtained from the present study: 1. Since acid sulfate soil contains many acid things such as sulfuric acid ion (SO₄^2-) etc., most of the calcium hydroxide in soil is used by neutralization. 2. The lime-treated soils become strong gradually by increase of mixture rate and curing period and become brittle material. 3. The strength property of the lime-treated soils is closely linked to the formation state of etrringites.

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  In this study, a new non excavation purification method for machine oil polluted ground was examined. The method is pushing machine oil away by the vegetable oil within the flow of horizontal continuous oil phase. The laboratory experiments with soil tanks were conducted and expected oil flow was formed. Machine oil was flowed out to the recovery well. But the thin machine oil layer was formed below the injected vegetable oil. This thin machine oil layer will be difficult to remove iu-situ. From the results of additional experiment using the biodegradable surfactant together with the vegetable oil, machine oil layer was emulsified and flowed out to the well efficiently.

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