Japan suffered from severe damage to levees, such as cracking and subsidence due to earthquake-induced liquefaction, infiltration failure and flood hazard due to intensive downpour. Currently, as one of major countermeasures for levees against these disasters, installation of sheet-pile, or soil improvement is executed at the foot of the embankment. However, these countermeasures were occasionally found to be insufficient. Therefore, we studied the applicability of a new type of countermeasure using a hybrid structure of soil and sheet-pile, which is installed at the top or shoulder of the embankment. In this paper, by conducting a series of model tests, we could confirm the effectiveness of the proposed countermeasure against various disasters.

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In this paper, a case study was carried out into the mechanical behaviour of a largely-deformed reinforced earth wall. The engineering properties of the fill material were in detail examined by performing various in-situ as well as laboratory tests such as surface wave survey, PS-logging, RI-logging, bender element test, direct shear box test, soaking test, etc. Based on the results of these tests, the process to reach a large-deformation may be described such that i) a considerable amount of settlement was induced over a weak soil layer in the reinforced earth due to infiltration of rainfall water, ii) the part of fill material was partially supported by the geotextile, and iii) the concrete panels were excessively deformed by the unexpectedly large tension force of the geotextile, and also by the decrease of shear resistance between the geotextile and the surrounding soil owing to the decrease of the overburden stress.

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According to the Japanese deep-well database maintained by the Land, Infrastructure and Transportation Ministry, many deep wells are partially penetrated, featuring multilayered screens as a result of the geological features of the auifer. This is a serious problem not only for the effective use of underground water as a water resource but also for the conservation of the water environment. As part of well design in such auifers, it is necessary to consider the cost of construction and estimate the design pumping discharge as accurately as possible. However, it is difficult to apply general well theory accurately to the calculation of the hydraulic constant and to pumping groundwater control for partially penetrating wells. Inappropriately designed pumping discharges often result. Therefore designs based on such calculations tend to lead to a drying up of the well through excessive groundwater pumping. Furthermore, the damage caused by subsidence of the ground because of the lowering of the groundwater level also increases. In this study, we propose a practical well loss estimation method that includes consideration of hydraulic geological features of an auifer using pre-boring, step-drawndown testing and Thime-Dupuit’s euilibrium theory to estimate safe designs of pumping discharges. This is a method different from Jacob’s method based on non-euilibrium theory. We examine the effectiveness of our proposed method, and conclude that it is possible to manage groundwater in auifers with partially penetrating wells using the new method. Furthermore, we elucidate that it is possible to apply the new method to groundwater in any geological structure.

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In this study, a practical test apparatus was developed, which can be used for triaxial compression tests of unsaturated soils, by using 2 common triaxial cells for saturated soils and improving their top cap and pedestal. It was shown that shear properties can be discussed with this device by running a variety of accuracy examinations on the developed test apparatus, which is only a slightly improved common triaxial test apparatus. Furthermore, by using compacted weathered granite soil at low lateral pressure conditions, a drained shear test at constant suction was executed with this apparatus. Thereafter, measured shear strengths were compared to shear strengths obtained from the estimation approach proposed by Öberg and Sällfors. From the results of the comparison under these conditions, the following knowledge could be obtained.
1)Shear strength estimations obtained from the approach proposed by Öberg and Sällfors result in lower shear strength than the values obtained from the test apparatus. The difference is attributed two factors. One of them is the difference of contributions to shear strengh by dilatancy, which depends on suction changes. The other is the difference of cohesions between unsaturated condition at suction “0” in wetting process and saturated condition.
2)The effect of the difference between estimated shear strengths of the conventional method and the measured shear strengths of the test apparatus on slope stability analyses of embankments in wetting process may not be neglected.

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In order to carry out the preventive maintenance control of expressway slopes, it is important to accurately understand the ground condition of slopes, followed by estimating the damaged area. Such ground condition is presently investigated by boring and/or physical prospecting on the slope surface. For the slopes widely distributed along expressways, however, a change of direction from the present corrective maintenance control to the preventive one is required. Therefore, it is indispensable that the critical slopes can be detected efficiently and economically. In this paper, an experimental investigation was carried out, applying the helicopter electromagnetic (HEM) method, by which the ground resistivity distribution of wide area can be detected, to some available expressway slopes. Based on the investigated data, the influence of the different prospecting techniques of HEM and the metal obstacles of slope reinforcements on the resistivity, and the estimation reliability of ground condition due to the resistivity were examined. As the results, it was confirmed that the ground condition of slopes can be understand effectively by the HEM prospecting data, especially detecting the areas of high volume water content. Finally, the applicability of HEM to the preventive maintenance control on expressway slopes was elucidated.

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In conducting the general check for D-runway project at Tokyo International Airport (Haneda Airport), the proposed soil stratum estimation based on Kriging was done by using the boring data extracted from the type of soil data base and a three-dimensional stratum was estimated for the selected area.
In this thesis, the result was revised using the additional boring data conducted for the detail design of this project. As a result, the original three-dimensional stratum estimation was found useful as the fundamental estimation to show the effectiveness of the proposed method.

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Sand compaction pile ground improvement method (SCP method) has been applied for soft clay layer beneath gravity-type quay walls in order to increase the ground stability. In the improvement method, solidified iron-and-steel slag is considered to be used as ground improvement material instead of exhaustible sand. In this study, a series of centrifuge model tests and circular slip analyses were conducted to investigate the stability of ground using iron-and-steel slag. Some types of soil materials were chosen as the improvement material for the backfill loading model tests. The model grounds using sand and slag showed the same ground deformation mode to the failure state. In addition, the displacement in the slag case was found to be smaller than that in the sand case.

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In the past, authors have clarified that the behavior of the pile foundation when the liquefied ground flows in the sloping ground by conducting the model shaking table test under 1.0g gravitational field focusing on the interaction between the pile foundation and the surface non-liquefaction layer. It was confirmed that the surface non-liquefaction layer greatly influences on the pile foundation behavior when the liquefaction and the ground flow occurred.
In this study, the influence factors such as extent of the thickness, the stiffness of the surface non-liquefaction layer, the ground inclination, the base input vibration etc. on the pile foundation behavior were examined by conducting additional tests when the liquefaction and the ground flow occurred.
As a result, it was clarified that influences of the thickness, the stiffness of the surface non-liquefaction layer and the ground inclination level on external forces acting on the pile foundation became large during ground liquefaction and after shaking although it was small in the process to liquefaction initiation.

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Permeability of alluvial fan deposit is variable with how fully matrix is packed, matrix packing level. In this study, undisturbed gravelly samples are divided into two parts by optimum calculation based on matrix packing levels. Matrix part is one part in which matrix is fully or almost fully packed, and water passage part is the other part in which matrix isn’t packed enough. A distribution model of permeability is induced by the arithmetic mean of the permeability of matrix and water passage parts weighted by their thickness. In the Toyohira-gawa river Alluvial fan, especially on Sapporo-surface, the optimum equation by setting four matrix packing levels I to IV can calculate the permeability to be nearly equal, ranged between half and double, to the measured one. This model is effective to estimate in-situ permeability of alluvial fan deposit. In addition, this model is expected to be applied to estimate heterogeneity by inferring the detailed distribution of permeability. The vertical distribution of permeability in the Toyohira-gawa river Alluvial fan indicates strong heterogeneity between adjacent points. The variogram of log(K’) reveals that the macroscopic heterogeneity occurs at observation distance in excess of 5 to 10 meters.

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Engineering properties of waste glass is evaluated and discussed in this paper. Firstly, the basic properties of a waste glass were examined by performing the physical properties test as well as pH test. Secondly, the deformation and strength of waste glass were measured by bender element test, direct shear test and triaxial cyclic loading test. Finally, consolidation test was carried out to examine the effect of evaluate waste glass content to improve the compressibility of a silty soil. Based on the results of these laboratory tests, a practical implication is posed how we possibly improve the properties of waste glass fragment in use for geotechnical engineering works.

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In order to examine the mechanism of shear deformation and compression of sandy slope due to rainfall, the measurement of the deformation and volumetric water content, suction were conducted during artificial rainfall and after rainfall in the sandy model slope. As results, shear deformation and compression in the slope were in progress not only at absorbing process during rainfall but also drying process after rainfall, and sometimes under the condition of constant water volumetric content or suction. They were generated at when wetting front reached the base of the slope layer. The increase of compression or shear deformation at shallower layer was relatively small at wetting process, while that at deeper layer was large with the increase of water volumetric content or the decrease of suction.

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