To estimate the degree of consolidation settlement, the soil mass conservation principle was used in this analysis. The specific storage coefficient was treated as a function of effective stress and void ratio. With this method, the behavior of consolidation from over-consolidation state to normal-consolidation state is easy to analyze. To evaluate its validity, results from the new method were compared with those from laboratory tests and Terzaghi's one-dimensional analysis. From these comparisons, it was shown that the principle is very accurate and reliable for estimating ground settlement. The new method was also used to analyse field conditions and to estimate settlement arising from (a) dewatering (pumping), (b) double-step load landfill phenomenon and (c) the disruption of groundwater flow during underground construction.

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In this paper, laboratory tests was performed to investigate the undrained strength characteristics of embankment soil using cement-stabilized muddy soil. The test results shows the followings.
The strength characteristics of the embankment soil prepared by cement-stabilized muddy soil is affected by confining pressure in laboratory tests that relate the cementation bond of cement-stabilized soil specimen. The shear strength parameters of the embankment soil can be expressed by the bi-linear type failure criterion intersecting at the confining stress.

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To examine the mechanical interaction between twin parallel tunnels, 2-dimensional trapdoor experiments are conducted under varied: overburden and tunnel excavation sequence. From experimental results, it is found that earth pressure acting on twin tunnels is larger than that acting on a single tunnel; it is ovserved that earth pressure acting on the first tunnel reaches the overburden pressure. Authors propose a simple method for estimating the earth pressure acting on twin tunnels by considering Terzaghi's theory. Applicability of the proposed method is checked by comparing calculation results with experimental results. It is found that the proposed method can estimate the earth pressure acting on the first and second tunnel.

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Settlement behavior of piled raft foundations on a natural deposited soil is numerically investigated in terms of the load transfer mechanism. Three-dimensional soil-water coupled deformation analyses are performed by modeling the piled raft as an elastic material and the soil as an two-phase elasto-plastic material. The followings are mainly clarified. Piled raft significantly reduces the settlement because the applied load is transferred through the piles into a deeper soil layer that is less compressive, and the outer piles mobilize the greater friction resistance. The more uniformly and/or the more outside the longer piles are arranged on the raft, the smaller the settlement and the greater the load sharing ratio of piles.

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To study effect of particle shape on mechanical behavior of granular material, simulations for biaxial compression and shear tests were carried out using specimens of different particle shapes. Obtained results are analyzed based on the FU value, which gives the roundness of the particle for sphere. The compression index, the internal friction angle and the coefficient of dilatency at failure depend on the particle shapes, even if they have the same physical properties. The shear resistance coefficient at the maximum compression state, which has relation to the shear resistance coefficient at the critical state, are almost the same values for different particle shapes.

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The mechanical effect of the shotcrete as the countermeasure against the key-block falling in the rock tunnel is considered by using the rigid-plastic finite element method. It is noted that the adhesive strength of the shotcrete to the rock mass is the most important factor to avoid the bending and peeling failure mechanism. The small adhesive strength causes easly the peeling off of the shotcrete from the rock mass which results in the bending failure with a relative long bending span and a small loading capacity. The minimum value of the adhesive strength is evaluated to be the half of the strength of the shotcrete so that no bending failure nor peeling failure occurs.

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After completion of a tunnel, constructed in soft rock, some deformations and cracks were observed on the lining. This situation is 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 reinforcement to repair the tunnel based on monitoring the deformation progress. In this paper, long-term measured tunnel deformations is simulated by means of rock strength degradation model located around tunnel, and subsequently affection of the deformed lining is considered.

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Various field investigation with laboratory tests on undisturbed samples were carried out to examine and confirm possible causes of a damaged shield tunnel, inferred by the observations of centrifuge model tests. A series of elasto-plastic coupled FEM analyses were also conducted to examine the influences of various factors, such as the thickness of soft clay and hydraulic boundary conditions of lining, on the long term lining load.

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A new rational design method for buried pipelines subjected to differential ground settlement was proposed on the basis of a data set from 3-D centrifuge model tests. The proposed method considers both marked earth pressure concentration on the upper-halves of pipelines and change in the length of the area with the earth pressure concentration, predicting well non-linear change, observed in the centrifuge model tests, in the pipeline response (earth pressure and deflection) due to increase in differential ground settlement. Its validity, as well as its superiority against a current design standard, was confirmed through comparison with the results of the centrifuge model tests.

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An investigation of hydraulic confining system, in which gas leakage would be prevented by surrounding underground water, was conducted using measurement data that was acquired in an experiment of compressed air storage in underground rock cavern for demonstrating hydraulic confining system. Hydraulic confining system would consequently function under two conditions, in which (a) there's no air leakage or (b) a water-air interface moved statically, depending on a relationship between gas pressure and surrounding water pressure. It was also presumed that air leakage would not emerge because of very small relative permeability of air in condition (b), and that flow channel of air would be formed in higher pressure than that in condition (b). Relative permeabilities of air and water on saturated or undersaturated condition in rock around the cavern was also calculated to suggest relative permeability models which represent a relationship between air and water relative permeability well.

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A reclaimed land for New-Kitakyushu airport has been constructed on 2km offshore in Suo-Nada sea. In this site, the dredged soft clay is widely distributed below the reclaimed land, which is characterized as the highly under-consolidated soft clay ground. In this paper, a rational design method of the road embankment on under-consolidated dredged clay ground in the reclaimed land is presented to evaluate the vertical settlements and the strength increment s due to the construction of the road embankments. The key idea is in the treatments of the excess pore water pressure for the under-consolidated soft clay. It is verified that the presented method gives a good agreement with the results of the field measuremen

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Cone Penetration Test (CPT) is a simple in-situ testing method and can gain useful information in a short period of time. However, the CPT has not been used in practice in Japan. The purpose of this study is to verify applicability and reliability of the CPT to cohesive soils. In this paper, with actual data obtained site investigation results from different cohesive soils at 26 locations in Japan and overseas, it is shown that the cone factor is unaffected by sedimentation environment and local characteristics. Expressions are then proposed to estimate engineering properties of the cohesive soils with necessary and sufficient accuracy using various parameters obtained from the CPT results.

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Granulated blast furnace slag used for backfilling of quay wall is found to be solidified by several research programs. We now need to know when and how granulated blast furnace slag is solidified. In this paper, we report the change of strength property of actually used granulated furnace slag for backfilling. In the investigation, we found the development of the solidified area with time, and about 70% of the slag layer will be solidified after 18 months from the construction, the relation between SPT-N value and the solidified area. SPT-N value will be a simple index for solidification. Finally we report effect of the solidified slag to the anti-seismic deign of quay wall.

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A method of reflecting the strength of composite ground formed by deep mixing on horizontal resistance of piles was put into practice. In this design method, the necessary area of ground improvement was set as the area raised to the working gradient of passive earth pressure from the depth of characteristic length of piles. And the horizontal subgrade reaction of piles was introduced from the modulus of deformation of composite ground. The same horizontal resistance of pile as the design was obtained from on-site horizontal pile loading test in composite ground, which supported the reliability of the above process. It revealed that the application of this method to the design of abutment foundation caused much reduction of cost compared with to the current method.

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The effect of pore water on solidification of granulated blast furnace slag, called slag for short hereafter, is discussed in this paper. The effects of pH and the concentration of Ca²⁺ are mainly discussed. When the pore water was sea water, pH of the pore water was not enough high and slag solidified. When the pore water was with NAOH solution, the slag did not solidified over than 90 days of curing in spite of its high pH. Duration needed to slag solidification was longer than the case the pore water was sea water. These results mean not only high pH but Ca²⁺ concentration affects the solidification of slag.

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