A soil/water coupled finite element program (DACSAR-F) is coded based on finite elasto-plastic deformation theory. Cam-clay model is incorporated in the program. Then, the localized deformation developing in the normally consolidated clay specimen subjected to plane strain compression shear is numerically simulated. The transition of localized deformation mode is examined and the mode change of localized deformation is discussed. Emphasized is the dominant role of pore water migration inside the specimen to the change of localized deformation mode.

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In case of large-scaled bridge foundation of soft rocks such as weathered granite, it is important to evaluate deformation characteristics of bed rock properly for predicting deformation and rational foundation design. As the results of underground displacement measurement during construction, the authors have made to conclude as following points. In the range of the rock mass classification D_H and C_L at the survey point,
(1) The deformation characteristics depends on the strain level in the shallower zone.
(2) Whichever the rock mass classification, the deformation characteristics depend on the restrain in the deeper zone.
(3) The deformation characteristics depends on the large-scaled excavation in the near surface zone.

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Precast concrete culverts have an advantage of saving construction cost through shortening of job duration. However, on precast concrete structure, several analytical problems of design of connection joints have not been resolved yet. In this paper, a structure system of a prestressed precast culvert is proposed, which connects precast concrete elements by high deformable rubber-joints and is unitized by PC steel strands, so that the superior axial flexibility and watertight are performed. Accordingly, this structure is able to follow ground subsidence or severe earthquake deformation. An analytical method and a computer program have been developed to calculate continuous beams with non-linear elastic spring joints on elastic foundation. This model is possible to estimate the change of effective prestress on the rubber during construction stage and service period.

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A design method for buried flexible pipes based on anew concept of soil-structure interaction phenomenon is proposed to improve the current inadequate design procedures. Vertical deflections of buried pipes and maximum bending moments produced in the walls of the pipes were calculated by elastic finite element analysis. They are summarized as design charts for deflections and maximum bending moments in pipes in terms of the flexibility index of buried pipes (k), which is defined as the relative stiffness between the pipe and the surrounding soil. The new design method predicts actual pipe behavior reasonably well and therefore will be useful to prevent frequent damages to the buried pipes that occur throughout the world.

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A series of laboratory model tests was carried out to clarify the effect of rate of loading and thickness of soil layer on highly organic soft ground due to embankment construction. An estimation method was proposed for settlement of embankment and heaving of surrounding ground surface during embankment construction.
On the basis of experimental results, it was found that the deformation characteristics of surrounding area were related to the rate of loading (v_p) and thickness of soil layer (D₀). Furthermore predictions by proposed method was found to have a good agreement with in-site measurement.

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In case of constructing underground structures in deep conglomerate, it is considered that strength and deformation properties of conglomerate core samples are occasionally overestimated because of gravel effect, while the properties are underestimated because of sample disturbance by core sampling. A series of laboratory tests was therefore performed using deep conglomerate core samples and the quality evaluation of the samples was conducted. In this paper, it is presented that the sample disturbance which gives influences to the quality of the samples is complicatedly concerned with gravel fraction content and calcite content. Especially the smaller the calcite content and the gravel fraction content are, the more extensively the sample disturbance is influenced.

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A rational method of evaluating the skin friction of cast-in place piles in sandy soils is presented on the basis of geomechanical considerations. A critical state friction angle is shown to be effective as a design parameter to evaluate the skin friction. An empirical equation for coefficient of horizontal stress was also proposed on the basis of a few considerations of the soil-pile interaction mechanism. In addition, utilizing this proposed equation, the mean horizontal stress acting on piles was derived, to calculate rationally the total skin friction in piles. The applicability of the model is verified through the use of a newly developed in-situ friction test, a lull scale pile load test in volcanic ash ‘Shirasu’ ground and comparison with the data-base of pile load tests.

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The sand compaction pile (SCP) method is the most commonly used soil improvement techniques. In present design of the SCPs method, the SCPs are assumed to be fully penetrated up to the bottom of the clay deposit. However, there are many cases where the SCPs are partly penetrated to the bottom of the clay deposit because of the construction cost, the capacity of construction equipments and other factors. In this research, a series of model tests was carried out in order to clarify the consolidation behavior of the clay ground improved by the partly and fully penetrated SCPs. As the results, it was found that the stress concentration ratio of model ground improved by partly penetrated SCPs varied with time and depth and this ratio was dependent on the penetration depth of SCPs.

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In the ecavern excavated in hard rock, failure model is dominated by the slip slide or fall of jointed rock. In this paper, it is shown how to predict the frequency of keyblock and to evaluate supporting by joint data got from site investigation data

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Time dependent earth pressure on support system in excavations is investigated through the soil-water coupled finite deformation analysis employing the subloading Cam-clay model. In this study, two type of ground conditions (1) a ground which can self support the excavation, (2) a ground which can not self support, are considered. Due to pore water migration within the soil, lateral pressure initially increases with time finally reaching a constant value. In ground (1) the support system is exerted by higher lateral pressure when the support is introduced just after the excavation.
The pressure on supports reduces significantly when the installation is delayed. However, in ground (2) there is no much deference in pressure even with delayed support installation.

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Active mobilization of bearing capacity of surrounding rock mass characterizes the NATM concept of supporting. There have been many attempts to give quantitative expressions for this capacity, but no one has ever completely succeed. The authors have carried out a strict solution of a circular tunnel in an elastic ground and showed that the bearing capacities of a tunnel lining, the surrounding ground and the total can be evaluated quantitatively by a common index, ‘support-stiffness’. By advancing the above analysis, in this paper, the support-stiffnesses and the strict solution are utilized successfully to construct a theoretical characteristic curve of tunnel-support. This characteristic curve is helpful in understanding the formation of the Fenner-Pacher curve in actual tunnelling.

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Geosynthetic-reinforced soil wall has been widely used. Because of the flexibility of geosynthetic which can follow the deformation of soils, it is desired to clarify the mechanism of reinforcement considering the tensile deformation of geosynthetic. Developing the model device for reiforced soil wall, a series of tests was carried out on three kinds of reinforcements with different tensile stiffness and two kinds of backfill materials. Comparing the results with that of non-reinforced case, the tensile force applied to reinforcement was investigated. Additionally, the distribution of tensile force in reinforcement was measured varying the tensile stiffness of the materials.

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The purpose of the paper is to investigate experimentally the effect of skew angle of a roller cutter positioned in the center part of a tunnel boring machine on the amount of excavation and wear against granite and two-pyroxene gabbro. The radial cross section of the tip of roller cutter was designed to be trianglular shape for increasing the amount of excavated debris. The experiment was executed for a skew angle from 0 to ±π/9rad and a normal load of 0.98 to 11.8kN. As the results, it was observed that, the amount of excavation of two-pyroxene gabbro increases with skew angle and the amount of excavation per unit work has peak values at skew angle of ±π/36rad, after that it increases with skew angle, the amount of wear can be expressed as the exponential function of skew angle, normal load and rolling distance, and that the optimum skew angle to maximize the amount of excavation per unit work and minimize the amount of wear is ±π/36rad.

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In order to investigate the cementing effect of volcanic cohesive soils in their in-situ condition, the authors conducted constant volume direct shear tests together with standard consolidation tests on Takadate loam soils which locally distributes over Nanbu District of Aomori Prefecture and a Kanto loam soil which exists is in Hiratsuka of Kanagawa Prefecture. The cementation produces a higher consolidation yield stress than overburden pressure and a marked effect on the shear strength in over consolidated region up to the consolidation yield stress. The cementing effect is weakened by the consolidation pressure and the freeze-thaw action.

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A newly developed Self Boring In situ Friction Test (SBIFT), is presented. As a multi-purpose technique, it is aimed to evaluate soil/soil-structure strength, coefficient of subgrade shear reaction, deformation moduli and earth pressure at rest. Firstly, the device is introduced. Then theoretical background for interpretations required is discussed. Examination tests in the laboratory with the probe of SBIFT were conducted to investigate the technique's reliability. And, in situ SBIFT in various soils were conducted and compared with other tests' results. The conclusions are that the friction strength, subgrade shear reaction coefficient and deformation modulus can be interpreted, and the earth pressure at rest be possibly interpreted by SBIFT.

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Triaxial compression test was performed on two set of parallel grading samples, which were composed of crushed rhyolite and granite, respectively and compacted to 90% of relative density. Finer and coarser samples of granite showed same relation of confining pressure and shear strength, however, the finer sample showed higher strength for rhyolite. It would come from the flatter grain shape of finer sample. The nature of decreasing secant moudulus of shear strength with increasing confining pressure was due to the flatness of grain shape, too. On the other hand, crushing of grain during shearing seemed to no influence on shear strength.

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Damages of houses and buildings by the upheaval of the Neogene mudstone foundation are observed in many regions in Japan. The upheaval of the ground was previously attributed to the expansion of the soils caused by the appearance of crystals of gypsum by the chemical weathering; the ground water containing sulfate ions goes up by the capillarity caused by the drying of the ground surface resulting in the concentration of sulfate ions. The concentrated ions react with calcium ions to produce gypsum crystals. However, as the damages were not universally obseved through Japan, the author perceived a participation of some bacteria in producing sulfate ions.
Further, the author investigated the effects of the upheaval of the ground on the wooden and concrete constructions on the Neogene mudstone, and discussed the results thus obtained.

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Method of estimating the pore volume in rock mass has been described. The pore volume is obtained by using the data of the “vacuum-permeability test” which is a method of detecting the loosened zone in rock mass from the air permeability distribution characteristics. To get the pore volume, the airflow rate and the pressure reduction in test section are analyzed during the field measurements and the calibration test executed within the highly sealed steel pipe. The reliability of this method has been confirmed by laboratory test, and some examples of field measurement have been shown.

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Based on the idea of wrapping a part of foundation like a soilbag, a new reinforcing method for bearing capacity is proposed. The validity of this method is illustrated by the results of the model footing tests and the model vertical embankment tests. Then, as an application example in the real engineering practice, a reinforcing method utilizing soilbags for the ballast foundation under the railway sleeper is stated and its validity is demonstrated by model tests. So far, the soilbag has been mainly used to prevent a flow of soils from water. In this study, however, the mechanical meaning of the soilbag is studied on the basis of the dilatancy characteristics of granular materials and it is found that the soilbag may be used as a load supporting body such as a footing or a pile.

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This paper describes the stress field of characteristic-line method for anisotropically consolidated saturated clays under plane strain condition at failure state. The undrained shear strength under plane strain condition is obtained from the elasto-plastic constitutive model proposed by Sekiguchi & Ohta which can represent the stress induced anisotropy, and thus obtained shear strength in terms of effective stresses is employed in the theory of characteristic-line field as failure conditions. By solving the partial differntial equations with the pore water pressure as an explicit variable, we obtain the distributions of total stress, effective stress and pore water pressure at the failure state.

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In-situ execution of soil improvement by vibrational compaction method with absorbing excess porewater pressure has been carried out for preventing the liquefaction of back-fill gravelly material (MASADO). The mechanism of ground improvement and the remarkable compaction effect of this method at gravelly soils were verified. The execution spacing became wider at the same target strength, this new method was cleared to be able to execute more economically and efficiently than the conventional one. Futher the accuracy of the suggested prediction method of improvement effect has been also confirmed.

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A new system of axi-symmetric triaxial freeze-thaw-shear testing apparatus is introduced. This system is developed to evaluate the shear parameters and their dependence upon freezing-thawing history of soil samples. Shear testing can be carried out immediately after thawing without any stress release between freeze-thaw and shear operation. It is found on the compacted clay that the frozen and thawed soil shows larger strength and smaller pore pressure development than those of unfrozen sample, however the effective shear strength parameters of isotropically or anisotropically consolidated unfrozen and frozen samples do not vary after the thaw settlement of the frozen soil is completed.

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The effect of pH on liquid and plastic limits of soils was examined based on present and previous results of liquid and plastic limits tests with changing pH, and on the mineral and chemical compositions of the soils. It was clarified that although pH has a very pronounced effect on liquid limits, its effect on plastic limits is slight. These results indicate that the pH-induced changes of the liquid and plastic limits are dependent on the structure of the clay minerals and the existence of cations between the sheets of clay minerals. Finally, it was shown that the pH-induced changes of the sedimentation and the microstructure of soil particles effectively clarify the changes of liquid and plastic limits with changing pH.

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A simplified simple shear apparatus and its test procedures were developed in this study. The reliability of the system was verified by comparing the test results of this system with those of the torsional simple shear tests conducted by Tatsuoka et al. (1986). Using this verified system, several types of liquefaction tests, such as stress controlled, strain controlled and on-line were conducted. The test results proved that this system was relevant to perform practical liquefaction tests.

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