Installation of pile foundation at the sites with subsurface contamination is required to prevent cross contamination beneath the aquitard. If the drilling slurry used in cast in place pile installation such as Earth Drill Method exhibits sufficient sorption capacity against chemicals of concern, installation of piles with less complex or expensive method preventing cross contamination will become possible. In this study, batch sorption tests were conducted to assess sorption capacities of suspended solids in the drilling slurry against arsenic (As), fluorine (F), and lead (Pb) for three different concentration levels. Three types of drilling slurry were used, namely polymer-dominant slurry, bentonitic slurry, and a slurry which was obtained from an actual construction site. Effects of the addition of magnesium oxide (MgO) and aluminum hydroxide (Al(OH)3) as the adsorbent were also evaluated. Filtered liquid samples obtained from API (American Petroleum Institute) Filtration Test were subjected to the chemical analysis. Experimental results indicated that suspended solids in drilling slurry exhibited high sorption capacity against lead. Addition of 5% MgO or Al(OH)3 enhanced the sorption capacity, and consequently satisfied the Japanese environmental quality standards for groundwater. Drilling slurry might function to limit the cross contamination, and advantageous against the sites where natural contamination exists above the aquitard.

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In order to dispose of dredged clay effectively, it is important to plan the dredged clay disposal based on the settlement prediction in advance and to understand accurately the acceptable quantity of dredged clay in the disposal pond. However, it is still a great challenge to understand properly the consolidation characteristics of the dredged clay for the settlement prediction. The purpose of this paper is, in the disposal pond at Kobe airport, to calculate the settlement of the clay using the volume ratio f represented uniformly by logf for the consolidation characteristics of clay (compressibility, permeability and consolidation velocity) and to compare the calculation with the measurements of various properties. Soil improvement was done in the disposal pond by the vertical drain using the difference in the water head after the dredged clay was disposed of several times, and then additional dredged clay was disposed of. The authors performed calculations with the proposed consolidation method against the bed of dredged clay with the complex complicated disposal history. It is reported that the results agree mostly with the measured settlement, pore water pressure and the water content at the site.

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A newly developed reinforced member incorporating both a bearing resistance and a friction resistance was confirmed the effectiveness using a prototype reinforced earth wall. The axial forces of the reinforcement members installed in the prototype reinforced earth wall were measured through a construction experiment and a field measurement. As a result, the measured axis forces of the reinforcement members increased during the construction of the reinforced earth wall. Then, the most of the axis forces of the reinforcement members were kept constant after the construction. The resistances by both the friction plate and the bearing plate occurred from the early stage of the construction, and then converged at the final stage of the construction. The measured friction resistance was greater than that of the bearing resistance at the upper part of the reinforced earth wall. On the other hand, the contribution ratio of the friction resistance decreased with increasing the overburden pressure, and converged to about 40 %.

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The purpose of this examination was to explain the internal stability of the ground reinforcing pile composed of the different two materials with greatly different deformation characteristics. This pile was consisting of the soil cement column and the nodular thin steel pipe of which elastic modulus and yielding strain were greatly different. The mechanism of internal stability for this pile was temporarily formulated using the punching capacity of the nodular thin steel pipe and the compressive capacity of this pile and then, the compatibility of the formula was experimentally verified. As the result, compared the design value to the limit value of the punching capacity, the design value provide assurance of the short-term safety factor (1.5), indicating that this pile become unified. In addition, the yield of the thin steel pile occurs the internal yield of this pile. The yielding compressive capacity of this pile is equal to the sum of the load of each material when the thin steel pipe reaches to the yielding stress. Furthermore, after reaching the internal yield of this pile, the deformation characteristics of this pile depends on the mechanical characteristics of the soil cement column because the thin steel pipe has already yielded.

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The long-term settlement behavior of reclaimed land was analyzed based on the observed data in the commerce and industry center and the eastern sewage treatment center located in reclaimed land in Hiroshima Bay. The coefficients of secondary compression of clayey grounds in the 2 sites were back-calculated from the measured settlements which have been observed for about 40 years and 20 years, respectively. It was found that, in the reclaimed grounds improved by sand drain method or in the reclaimed lands with no improvement, the back-calculated values of coefficient of secondary compression were close to those measured by the conventional consolidation tests before the construction. In the grounds improved by sand compaction pile (SCP) method, the back-calculated values of coefficient of secondary compression were close to those obtained in the laboratory test multiplied by the coefficient of settlement reduction which is used for the design of SCP method.

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There are many uncertainties involved in the shear characteristics during the vane shear strength development. Therefore, when the mechanism of the vane shear strength development becomes further clarified in the future, the vane shear strengths may be calculated more reasonably than at present. In this study, the shear characteristic around the vane was observed in an experiment where a vane shear test was simulated for the reconstructed test specimen obtained from the X-ray CT scanning to examine the developmental mechanism of the torque involved in the vane shear test. As a result, it was found that the shear zone was not developed in the perimeter of the vane during development of the vane shear strength. During the maximum torque development, the shear zone was formed throughout the perimeter of the vane, and it was inferred that the majority of maximum torque was developed due to the resistance caused by the soil sample located in the front side of the vane.

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This paper addresses the liquefaction disaster that significantly damaged houses and lifelines in Urayasu City on Tokyo Bay during the 2011 off the Pacific Coast of Tohoku Earthquake. Aiming at reconstruction and mitigation of damage during future earthquakes, subsoil investigation was carried out intensively in the city. It was found that the damaging liquefaction occurred in the reclaimed sandy layer near the ground surface as well as in the upper part of the underlying alluvial sand. The present paper provides detailed information about the liquefied ground and soil characteristics therein with special emphasis on relationship between building and sewage pipe damage extents and the locations of sand discharge during dredging works. Furthermore, undrained cyclic triaxial shear tests were conducted on undisturbed sand samples to show that the obtained liquefaction resistance is consistent with the resistance assessed by in-situ investigations and soil characteristics.

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Many coastal dykes were damaged and collapsed during the 2011 off the Pacific coast of Tohoku Earthquake. The application of double sheet-pile walls to dykes has been proposed as an effective reinforcement method against earthquakes and flood hazards. In this study, double sheet-pile walls were confirmed to be effective in reducing the settlement of coastal dyke on liquefied ground during a large scale earthquake with high acceleration amplitude and long duration based on shaking model tests. In addition, numerical analyses indicated that the countermeasure by double sheet-pile walls was very effective for high acceleration amplitude and long duration earthquake.

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A new cap with a slider structure was implemented to triaxial testing apparatus for measuring elementary behaviors of an anisotropic material. Top of a cylindrical specimen could displace to perpendicular directions against the loading axis and frictionless boundary conditions were given by the cap. Using this apparatus, six small strain tensor components of tuff including bedding plane were investigated during both uniaxial and triaxial compression tests. The results of uniaxial tests, using two specimens sampled in parallel and perpendicular orientations to the bedding planes, demonstrated tangent Young’s modulus in the bedding direction is 1.5 times larger than that in the perpendicular direction. The anisotropy of Tage tuff assuming transversely isotropic elasticity is identified via proposed method by a single triaxial test using each specimen with inclined bedding plane at 15° or 45°. The results demonstrated that the dominant orientation of the anisotropy agreed well with that of the bedding plane, and anisotropic stiffness values obtained from a single triaxial test were close to those by uniaxial tests.

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In the construction project of 4th runway of Tokyo International Airport, the evaluation of strength of clay layer was carried out with various methods, such as unconfined compressive strength, the recompression method by triaxial test, the combined method with unconfined compressive strength and triaxial compression strength and the strength of triaxial UU test. By discussing the results of the tests, the quality evaluation of undisturbed samples and the estimate of strength obtained by triaxial UU test. It was found that the unconfined compressive strength of low plastic clay samples, the liquid limit of which are less than 40%, were reduced by the serious disturbances not dependent on the depth. However, the quality of samples, the liquid limits were equal to or larger than 40%, were good. The strengths obtained by triaxial UU test were evaluated as “adequate” or “good”, suggesting that the reduction of strength due to crack-type disturbance in unconfined compression strength was recovered in triaxial UU test.

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Recently, a methane hydrate-bearing layer located near the islands of Japan has been investigated as a new potential energy resource. This study examined the feasibility of in-situ ground improvement technologies for enhancing carbonate precipitation in the pores of the turbidite layer. First, the authors isolated urease producing bacteria from this methane hydrate-bearing layer in the Japan Sea. Then, two types of laboratory tests (a particle growth test and soil strength improvement test) were conducted using the in-situ microorganisms isolated from the seabed. The main findings of this research are as follows. 1) The urease-producing bacteria inhabit the methane hydrate-bearing layer near the islands of Japan (Pacific Ocean side and Japan Sea side) , 2) The urease-producing bacteria live under high and low salinity conditions, 3) The urea hydrolysis speed is slower than that of other bacteria such as Bacillus pasteurii (1/5 or less), 4) The microbial carbonate precipitation process can increase the particle size compared to that of the original particles coating the calcite layer surface, 5) The mechanism for increasing the soil strength is based on the addition of cohesion as well as a cement treated soil.

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