Reclamation by dredged clay is a self-weight consolidation process with increasing thickness. In order to predict the elevation of reclaimed ground and to predict the future settlement, it is absolutely necessary to have the reliable information on the rate of soil solid volume discharged into the reclaimed land. However, dredging is planned and recorded based on the total volume of soil including pore water. If there is a lack of test data on the water content of discharged dredged soil, the solid volume becomes uncertain and the prediction becomes impossible. The authors proposed a procedure of determining the rate of solid volume based on the soil investigation of already completed part of reclaimed soil and back analysis of the reclamation. The practical use of the proposed procedure was verified by the case record of New Kitakyushu Airport construction on the disposal pond.

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It is considered that a tunneling method without or reduction of mucks is possible to use for the case of tunnel excavation under the seabed where the surface displacement due to excavation is allowed. However, the behavior of the ground due to excavation has not been clarified yet for this situation and besides, the development of an effective tunneling method should be expected for such cases. The purpose of this study is to conduct model loading test with X-ray CT scanner in order to verify the effect of cutting shape of tunneling on the passive failure region. And a series of centrifuge modeling test are also conducted to check the in-situ stress level of the behavior. Based on all the test results in this study, an effective tunneling method, especially the shape of the cutting face, is proposed and this will be able to be one of new tunneling method to reduce the volume of mucks.

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Influence of void ratio on the shear stress increment due to dailatancy is examined by unsaturated triaxial compression test. The shear stress increment is caused by the positive dailatancy (dilation) at dense sand, and increases shear strength. Linear relation is found between the shear stress increment and state parameter at failure state. State paramenter is defined as ‘e (present void ratio) - e_cri. (critical void ratio)’. Critical void ratio is affected by present stress condition. As the state parameter increases, the shear stress increment decreases. And this decreases until 0 at ‘state parameter is 0’. Same linear relation between shear stress increment and state parameter at any moment during shear is also confirmed.

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In this paper outlines the observations made on the change in permeability when an aqueous calcium solution was left to permeate a material consisting of sodium bentonite mixed with different quantities of sand over a set period of time. The Ca substituted test specimen was then subjected to a triaxial compression test to determine the effects of Ca substitution on shear strength.
An increase in permeability was observed as sodium ions were discharged from the sodium bentonite specimen when the aqueous calcium solution was left to permeate over a set period of time. Results of the quantitative analysis of the Ca substituted test specimen performed after the mechanics test indicated that the Ca substitution ratio was between 75 and 98%, with Ca substitution being confirmed. Results of a triaxial compression test to determine shear strength indicated that the Ca substituted bentonite sand mixture specimen with different quantities of sand displayed a higher shear strength than that of the sodium substituted specimen.

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Microstructure of cement treated soil cured under an overburden pressure was observed and estimated using a scanning electron microscopy and a mercury intrusion porosimeter, respectively. The results revealed that total void volume of a specimen decreased with increasing the overburden pressure whereas the pore size and volume relation changed hardly. Also, cement hydrates in the specimen were identified and evaluated by X ray diffraction and ignition loss test, respectively. The effect of overburden pressure was not recognized in the composition and content of cement hydrates. The cementation property developing in consolidation and curing processes was not affected by the applying overburden pressure.

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A method to evaluate the thickness of the liquefied layer from the boiling sand appearing on the ground surface is proposed. The method is based on numerous shake table tests of sand ground with thin low permeable layer at the top. Sand boiling was observed on the ground top and lateral sides, and the area and the number of sand boils were counted. Both the low permeability layer and the Toyoura sand layer liquefied in tests. Based on this result, a relationship between thickness of the liquefied layer and number of sand boils per unit area was developed. The validity of the proposed equation is proven by the observation during the 2003 Miyagiken-hokubu earthquake.

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We propose a new approach using the seismic reflection profiling for estimating geological structures around shield tunnels. In the study including field tests, we found that an elastic wave (S wave) generated inside a shield tunnel transmits to the ground around the tunnel through its concrete segments and reflects at geological layer boundaries. In the proposed approach, the reflected waves are detected by geophones set inside the tunnel and geological structures above and below the tunnel are estimated through the date processing of the seismic reflection profiling. This approach was experimentally applied for an existing shield tunnel and the estimated seismic zones are consistent with the geological data observed by the boring survey.

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A compacted benntonite−sand mixture containing gravel has been developed for use as an impervious material. For the purpose of understanding a compacted benntonite−sand mixture containing gravel, the authoes investigated the effects of gravel content, bentonite content, maximum grain size, water content.
Laboratory tests have shown that the permeability of bentonite-sand mixture containing gravel is lower than that of a similar material which does not contain gravel. The coefficient of permeability of bentonite-sand mixtures, k, has a significant correlation with effective bentonite wet density (initial wet density of bentonite excluding gravel and sand portions). This method could also be applied to estimating the permeability of mixtures including bentonite.

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In the design of ground improvement to accelerate the consolidation of reclaimed land with dredged clay, the profile and consolidation parameters of such a ground are necessary. In the case of rapid construction, as time from the completion of reclamation by dredged clay to ground surface treatment is too short, a usual method based on ground investigation cannot be used. In this study, the determination method of ground model which is composed of profile and consolidation parameters is proposed based on the reclamation analysis, and its applicability is confirmed by the case records of construction of New Kitakyushu airport.

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Deep Mixing Method, a kind of in-situ admixture stabilization technique using quicklime, cement or their mixture as a binder, was developed in Japan and Scandinavian countries in 1970s. After then, a lot of research efforts have been performed on the strength characteristics of treated soil, interaction of treated and surrounding soils, development of new binder, development of new execution machine and technique, establishment of design procedure, and so on. The method has been widely applied to improve many varieties of soils such as soft alluvial clay and organic soil in many countries. However, long term property of treated soil is not throughout investigated.
Authors have kept two columns of in-situ treated soil with quicklime underground more than 27 years in order to investigate their long term property. Laboratory tests were carried out on one of them at 11 and 27 years' curing periods in order to investigate the long term change in the treated soil property. In the tests, unconfined compressive strength, wet density, water content and Calcium content were measured. For the 27 years' curing soil, needle penetration tests were also carried out to investigate the durability of the outer surface of treated soil. The series of the tests reveal that the treated soil cured for 27 years has gain three fold strength of original treated soil.

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A model for cyclic shear deformation under undrained condition is proposed as combining an effective stress path model with a nonlinear stress-strain curve. The effective stress path, which is given by a function of stress ratio with a harmony of two terms corresponding to positive and negative dilatancy, can express the cyclic mobility without using the phase transformation line. In order to couple to the nonlinear stress-strain curve with the effective stress path, the residual excess pore pressure buildup under undrained cyclic stresses is formulated as a function of accumulative shear work, which depends on the initial shear stress for sand and the strain-rate & strain amplitude for clay.

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It is quite important to mine ores with forming a stable retaining wall from the viewpoints of the safety for miners and the scenic preservation of the mine. However, there have been always a lot of the collapse of retaining wall. Four collapses in 2004, one in 2005 and two in 2006 occurred in the Shikoku, Japan. Therefore, the Shikoku branch of Chugoku Shikoku industry. safety and inspection department established a technical committee in the Chugoku Shikoku mine safety committee in 2005 and 2006. The technical committee summarized the present status of the retaining wall in Shikoku. From the summarized materials, all cases of the collapse of retaining wall were investigated. Moreover, they were reviewed and considered from the viewpoints of cause, foresight and provision.

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A study was conducted on the seismic behavior of piles in composite ground through non-linear dynamic analyses by using 2D FEM. As a result, displacement and strain of piles and ground deformation tended to be gorverned by the formation of composite ground. This behavior was similar under both level 1 and level 2 earthquake motions. It was also found that the influence of the improvement depth which is set as 1/β on the displacement and strain of piles was particularly significant. Ground deformation during earthquakes tended to decrease with an increase in improvement depth. Based on these findings, a seismic design method adequate for such piles was proposed and seismic issues were reviewed.

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Granulated Blast Furnace Slag (GBFS) has a hydraulic property and is expected as useful geo-material against liquefaction. In this paper, in order to clarify the cyclic shear strength in the process of hardening, the authors carried out the static shear tests and cyclic un-drained tri-axial tests for hardened specimens of GBFS with D_r=50% and 80%. As a result, it is observed that the dynamic shear strength increases proportionally with static shear strength and specimens with unconfined shear strength over 50kN/m² or cohesion over 40kN/m², show tensile break down without liquefaction in the cyclic un-drained tri-axial test.

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