In this study, we conducted a series of loading tests to investigate load support systems of a rubble rock foundation supporting a breakwater caisson. The test results show that the loading block is supported by a small number of contact points and the contact forces have a wide range of distribution. This discrete and inhomogeneous load support system of the foundation is very different from linearly distributed load support system assumed in the current design. As a result, the bottom slab of a caisson has larger bending moments than those predicted by linearly distributed load. The test results do not show a dependence of the load support system on the foundation surface roughness made by expert divers.

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Slaking phenomenon lowers the strength of rocks in cut slopes. In Shikoku, the slaking phenomenon is quite prevalent, especially in the Izumi Group where shale rocks containing expansive clay minerals undergo slaking easily. X-ray diffraction tests, however, show no expansive minerals in the shale, which means the slaking of shale is not only due to the swelling of the expansive minerals. Lab tests such as x-ray diffraction tests, analysis of water properties, etc. revealed that the shale undergoes slaking easily because mica and feldspar in it undergo structural changes in presence of water and due to loss of cementation by amorphous minerals.

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At present, two design methods are both adopted for shield tunnel receiving the history of the load; one is “The design method considering the history of the load” and the other is “The design method not considering the history of the load”. But, it hasn't been proved which is more rational. Therefore, to investigate the cross-sectional behaviour of such a shield tunnel, model tests in sand-box and the numerical analyses based on the above-mentioned two design methods are carried out. Consequently, it reveals that “The design method considering the history of the load” is more rational than the other one and in the numerical analyses, the Beam-Spring Model, in which ground springs set all around the tunnel lining, can explain the results of model tests better.

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This paper describes swelling and shear characteristics of a clay in a slip surface during an increase in pore water pressure due to rainfall, snow melting and so on. A saturated clay specimen before failure was subjected to such the increase in pore water pressure under a constant shear stress using triaxial slice shear test apparatus. As the pore water pressure inside the specimen is increased monotonously, effective stress path moves toward a critical state line. Shear strength mobilized on the slip surface decreases along the critical state line, simultaneously. During the increase in pore water pressure, relationships between an increase in void ratio and normalized effective normal stress or shear strength are determined by swelling index, respectively. Safety factor at first-time sliding can be approximately estimated by the changes in void ratio or pore water pressure.

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Recently, sensors that use an optical fiber have spread in the field of civil engineering. The BOTDR method to use an optical fiber sensor has a characteristic of continuous measurement for along distance. Sod is a soft and heterogeneous material. These features make it difficult to set and use a sensor on soil and maintain its accuracy also affected by grand water.
We carried out three types of experiment, two loading tests, a tensile test and a bending test. In this study, we estimated the conditions for measurement of the deformation of soil structures due to external factors by using an obtained fiber sensor. This paper describes an appropriate sensor structure to be used for soil structures.

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The mechanical behaviors of the two-dimensional uniform assembly of circular elements are studied by a simple model experiment and the rigid plastic limit analysis. In the experiment, the deformation patterns and the load-settlement curves of the partially-loaded ground are observed using the brass cylinders as the model of granular material while the frictional slippage and the rotation are assumed at the contact points of two elements in the rigid plastic numerical analysis. The comparison between the experiment and the analysis is quite interesting and discussed from a view point of applied mechanics.

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This paper describes a stability estimation of filling on soft ground under vacuum consolidation based on FEM analysis and case histories. Practically, the filling combination with vacuum preloading enables rapid construction on soft ground. However, the reasons why filling rate can be accelerated and how stability of embankment is improved are not clarified yet.
Stability mechanism of filling combined with vacuum preloading is presented using soil-water coupling FEM method. Based on that, stability control method is proposed. Its applicability and validity are examined through practical project.

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It has been 400 years since many castle masonry walls were constructed. Most of them are deformed and in the critical situation of collapse. In order to restore these masonry walls, as cultural properties, it is necessary to grasp their characteristics of deformation as correct as possible. First, the cross sectional shape of the castle masonry walls was measured. Secondly, it was examined whether the three design procedures are adaptable to the restoration of the walls. They are three manuals adopted in Japan in the past, “Gotou-ke Monjyo”, “Ishigaki Hiden-no-sho” and “Sekishou-sho”. As a result it has clarified that three design procedures can be formulated as three different equations. Besides, good correlation was found between the equations and the really measured values of masonry walls.

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A new soil stabilization method is studied as recycling excavated soils and slurry wastes from construction sites. This method is based on thorough distribution of cementation materials among liquefied soil particles. Stabilized soils flow like concrete mortar before hardening, require no compaction at the time of placing, and induce little volumetric changes in hardening. This paper summaries recently conduced studies on mechanical characteristics of the stabilized soils, such as relationship between specific gravity of slurry and amount of cement in terms of unconfined compressive strength, relative contribution of density and cement in mechanical characteristics, and remarkable soil properties necessary for a mixing design.

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The attempt was made to examine the changing of long-term load acting on established shield tunnel lining in soft clay ground, by using a series of centrifuge model tests, in which assumed that it was the influence by consolidation. Consequently, the changing of long-term load could not only be occurred by the condition of bottom drainage (which is well-known Marston-Spangler model), which considered from the former, and also it could be occurred by the condition of tunnel drainage. And, it was shown that deformation of the ground being controlled by existence of a tunnel and the stress in the ground being redistributed has caused the long-term load changing action.

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Frost heaving of the ground is strongly affected by thermal properties of soil. Temperature in soil, heat flux, frost heaving rate and frost penetration rate, etc. had been measured in natural ground at Kitami Institute of Technology from Nov. 2001 to May 2002. In this study, the characteristic of temperature gradient, heat flux and thermal conduction in soil were discussed. It became clear that thermal characteristics of soil are strongly related to the latent heat accompanied with frost heaving and frost penetration.

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The authors had carried out some kinds of trapdoor experiments and had discussed in detail the mechanical behavior of the ground during tunnel excavation. In this research, three dimensional trapdoor experiments and its numerical analyses were carried out with various overburdens for the purpose of investigating in detail and quantitatively the earth pressure characteristic and the deformation characteristic during tunnel excavation. Validities of analyses are inspected by comparing the analytical results with experimental ones. Moreover, Terzaghi's earth pressure theory and Arching theory are applied to the trapdoor experiments, and their applications are discussed comparing with experimental results and analytical ones.

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The density of absolutely dry conditions, the clay lump content, and organic impurity content of decomposed granite soil met all the quality standards for fine aggregate. Soundness by the use of chloride and standard sieve 75μm passing content, in contrast, did not meet all of the standards. The coefficient of water absorption met the standard for decomposed granite soil of Li≤2.5%.
Concrete compression tests were performed on two types of fine aggregate grain size distributions with three water-cement ratios. Results showed that the water-cement ratio had a greater effect than the grain size distribution on the compressive strength of the concrete.

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Since the outbreaks of huge earthquakes in Taiwan and Turkey in 1999, attention has been paid to surface fault rupturing causing damages to various civil engineering structures. The mechanism of surface fault rupturing is significantly affected by characteristics of fault movement and unconsolidated surface layer, and very little has been elucidated for the cases of strike-slip faults and oblique faults. This study examines a series of model tests of strike-slip faulting using sand. Characteristic features of shear band structures observed on the surface of model sand layer are investigated.

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Thermal expansion measurements of granitic rock at high temperature and confining pressure demonstrate the effect of fractures and fracture fillings. Based on mode of fractures, samples are grouped into those with: 1) no fracture, 2) a single artificial fracture and 3) a single natural fracture filled with materials. Results indicate that while fractures alone have very little effect on thermal expansion of the rock samples, fractures with fillings cause distinctive thermal expansion behavior due to contraction in fracture fillings during heating. Therefore, in evaluating rock mass thermal expansion behavior, the effects of fracture fillings should be considered in regard to fracture densities, compositions and thickness of fracture-filling materials.

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Special working ships, on which cement soil mixing plant and conveying device are pre-installed, have been deveoped and found practical applications in coastal engineering. Two examples of widening a dyke and building an embankment inside the reclamation by use of soft dredged soil are presented. Long distance transportation of the cement treated soil is an urgent problem to be solved. Though the working ships are able to convey cement treated dredging of natural water content by 250-300m, many projects require a transportation as long as 500m. Some improving ideas are discussed. Finally, a ground improvement method by use of the introduced cement treatment technique is suggested, so as to eliminate the disposal of dredging.

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Most of irrigation reservoir dams in Japan were damaged by a secular change because they were constructed over one hundred years ago. Such dams were mostly accumulated with a mud soil. This mud soil generally is high-water-content and very soft clayey soil. In order to make efficient use of such a problematic soil as embankment soil, we have developed a new type method to repair the damaged embankment by means of the stabilized mud soil with cement stabilizer. This paper describes an example of repairing work of the reservoir dam embankment that applied this method for the first time. It also represents the results investigated the strength and permeability characteristics of the embankment.

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In this study, the method of measuring the density of soil in situ with a split spoon sampler with built-in tubes was applied to a double-layer ground consisting of a sand layer and a cohesive-soil layer and its measuring accuracy was evaluated. The evaluation was made by comparing the wet densities, water contents, etc. measured with a radioisotope-cone penetration tester and those measured with the split spoon sampler. As to the cohesive soil, the wet densities, water contents, etc. measured with a thin-wall sampler were compared with those measured with the split spoon sampler and the radioisotope-cone penetration tester. As the result, the method of measuring the density of soil in situ with a split spoon sampler proved to be practical enough.

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The authors have proposed a method to predict the SPT N-value between piles by the sand compaction pile method. It is, however, found that the method tends not to predict large SPT N-values because the effect of the increase in K₀-values due to the compaction is not considered. In this study the effect of the K₀-value on the SPT N-value is taken into consideration to modify the prediction method. The modified method is examined with observed SPT N-values and a conventional prediction method called A-method. It is found that the modified method has higher accuracy than the original.

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