In Japan, since various kinds of small-sized pipes are buried in pavement under various conditions at shallow depth, it is necessory to establish a practical method to evaluate stress and deformation of the buried pipes induced by vehecle load. A simplified method to evaluate deflection and circumferential stress of small-sized buried pipe induced by wheel loads is proposed in this paper. The calcurated results were compared to the experimental results, finding the calcurated values gave a satisfactory agreement with measured values, which were obtained by field experiments.

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The disaster and the disaster prevention potential of landslides consist of the natural factors and the social ones. So, it is necessary for these potentials to evaluate for all of these factors. This paper aim at suggesting the method evaluating of these potentials and making the potential map using this evaluation. The multiple logistic model, which is based on the conception of multiple risks, is applyed for this evaluation. This evaluating value is regarded as the disaster potential, and the disaster prevention potential is evaluated by using the disaster potential. So, these potentials are expressed with probability. And then, some potential maps colored by the each potential are shown. These maps are useful for expressing not only the hazard zones but the effects of the prevention countermeasure considered the population.

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Since rock mass behaviour and tunnel support are influenced by volume changes along preexisting discontinuities, an understanding of these mechanisms is fundamental to tunnel behaviour prediction and reinforcement design. It is not clear that the prediction and the design are always suitable to the in-situ joint conditions revealed from tunnelling advances.
The proposed tunnelling method is directed toward improving practical applicability of the tunnel reinforcement design based on the jointed rock mass behaviour prediction. The joint behaviour model from Barton-Bandis is built on a fitting analysis of behaviour of jointed cores and in-situ joint monitoring by a “Joint Deformeter”. Jointed rock mass behaviours are predicted for a joint condition mapped on tunnel walls and for a reinforcement of rockbolt systems using a promising distinct element method (DEM). The procedure for the method is discussed from the standpoint of its in-situ applicability.

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This paper describes the effect of gravel content on mechanical properties of gravelly softrocks. Experimental study is conducted by using artificial specimens in which have marble as hard gravel and welded tuff as soft gravel. The following results were obtained. Fundamentally stress-strain relationships under shearing depend on the properties of matrix material. The equivalent modulus of deformation can be derived from gravel content, deformational modulus of gravel and that of matrix. Strength relation is nonlinear and it can be expressed by power function. Peak strength of gravelly rocks which take with strain-softening is smaller than peak strength of matrix. Strength relation of gravelly soft rocks can be estimated by gravel content, peak strength of matrix and residual strength of matrix.

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The soil reinforcement is expected to become an effective protection method in case that the soil liquefaction is anticipated to occur for the existing fasility. In this paper, the authors have investigated the effectiveness and reinforcing method by model test for various pattern of reinforcement. As a result, it has been became clear that the large friction and fixed head of reinforcement bars are very effective for prevention of soil liquefaction. Based upon the experimental results, they have also studied on the mechanism of reinforcement against liquefaction and suggested its evaluation.

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This paper deals with a proposal for settlement control of the earthfill or the embankment that is constructed on soft ground. This system is based on the settlement state space equation, the system identification method by adaptive observer. Following this, the settlement control methods, that also include the existing methods, are classified into three types. This paper shows a discriminate chart to judge the applicability of these settlement control systems, that can be utilized with the practical construction design and the site's works. By using this chart, we can also judge whether settlement can be finished within the construction period or not.

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Field measurements showed that the ram penetration of ground was proportional to the ram impact velocity and the impact duration; the impact duration was proportional to the ram mass of unit base area, not influenced by ram drop height. These facts lead to the idea that the ram penetration was proportional to the ram momentum and inversely proportional to the ram base area. This tendency was supported by the centrifuge model test and was also found in the ordinary laboratory compaction test. From these results, estimation of maximum acceleration, maximum impact force and maximum impact stress were discussed.

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Different five series of laboratory and outdoors slaking tests were carried out to investigate the resistibility of mudstone for slaking due to wetting-drying repetitions. Test results were analyzed using some indexes, those which are based on the grain size distribution obtained from sieve analysis at each cycle of the repetitions. These analyses concluded that the grain size distribution after slaking can be effectively evaluated by the negative binomial distribution, and two parameters prescribed the distribution were plotted on an unique relation curve depending on the maximum value of initial grain size distribution used in the tests.

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A series of undrained cyclic triaxial compression tests has been performed on high plasticity marine clays. Testing was performed on not only normally consolidated but also overconsolidated specimens under various combinations of overconsolidation ratio and cyclic shear stresses. At first, the effect of frequency on development of pore pressure and strain was investigated. Then, the cyclic shear strain amplitude was related with effective stress ratio at the peak of cyclic axial stress for normally consolidated sample while it was related with modified effective stress ratio for overconsolidated sample. A semiempirical model was proposed for evaluating the development of pore pressure and residual shear strain with number of cycles. The model successfully explained the behaviour of both normally consolidated and overconsolidated clays subjected to various cyclic shear stresses.

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The quasi-three-dimensional FEM which has used for composite ground improved by sand columns is arranged for composite ground of ‘lattice form’ which is assemblied by walls of sand. The proposed method takes into account the drainage to walls of sand. The proposed method shows well the characteristics of latticed composite ground on some tests by unit element. Analyses for the both composite grounds which are ‘column form’ and ‘lattice form’ are performed by the proposed method. Consquently at low replacement factor of sand the undrained capacity of the latticed composite ground is larger than that of the columned one. Stress concentrated to sand during consolidation is considerably different between the both composite grounds. It is clarified that the latticed composite ground has the advantage of the dissipation of pore-water pressure.

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The purpose of this study is to conduct a maximum and minimum densities test and a consolidation drained triaxial test, utilizing materials one of whose particle size, grain size distribution and grain shape is independently different, and to explicate how the primary properties of granular materials influence their void ratio and shear characteristics. The result is that the void ratio, the shear strength, and the dilatancy characteristics are greatly affected by the difference of grain shapes, but not much influenced by the particle size and grain size distribution. However, the modulus of deformation indicating the rigidity in the early stage of the shearing is uniquely determined by the volume decrease potential, irrespective of any one of the primary properties.

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Cyclic undrained behavior were investigated by means of triaxial and torsional shear tests on undisturbed and reconstituted samples of two kinds of sands including fines. Based on the test results, a simplified method is proposed for the estimation of liquefaction potential of sand deposit by critical number of loading cycles, (N_c)_cr. The estimated liquefaction strength curves for six kinds of sand deposit were almost coincident with test results until the double amplitude axial strain becomes around 2%, verifying a considerable potential of the proposed method.

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Blocks of undisturbed sample of a natural sedimentary sand called here Hayakawa sand were procured from the construction site of a pneumatic caisson. A series of drained triaxial compression tests and one-dimensional, isotropic consolidation tests was performed on the undisturbed and disturbed samples to investigate their stress-strain relationship and strength behaviour in view of soil structual characterristics, namely, particle crushing, anisotropy and cementation. The Hayakawa sand particles were crushed more by shearing than by isotropic compression at the pressure of around 3000kN/m². The undisturbed Hayakawa sand exhibits slight anisotropy at low stress levels and the anisotropy becomes less marked as the confining pressure is increasing. The Hayakawa sand had very small amount of cohesion of as small as 5kN/m². The deterioration of the cohesion was nicely modelled in an exponential manner proposed by Ooi et al..

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When 2-dimensional seepage flow experiments along/below a vertical sheet pile were made using sandy soils in laboratory, it was observed that a lot of air bubbles were formed in the sand during the seepage process. Those air bubbles were also observed to trigger a progressive failure of the sand deposits around the sheet pile. A series of seepage tests are again carried out by changing the degree of saturation of seepage water with dissolved air, and the mechanism of the air bubble formation in saturated sand that should happen with time under seepage flow application was found due to over-saturation of seepage water with air. Although the extent of the bubble formation depends on hydraulic gradient, confining pressure and grain size distribution of sand, those air bubbles may cause progressive failure of sands under even low seepage force.

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This study presents theoretical and experimental investigations into the strength-deformation characteristics of sand under cyclic loading. A constitutive relation for expressing the inelastic behaviour of sandy soil is proposed based on experimental data. The theoretical aspects are based on a plasticity theory framework. The effect of non-coaxiality was progressively incorporated in the model and was found to be very effective, particularly for modeling the behaviour of sand during unloading or reverse loading. A comparison between predicted and actual results for undrained cyclic shear tests shows that the dynamic strength-deformation characteristics of sands can be satisfactorily simulated

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This paper is concerned with a further extension of the authors' back analysis methods presented previously to non-circular slip surfaces. where the Morgenstern-Price method (M-P method) is used to express the factor of safety. Back analysis based on the M-P method is rather complicated in comparison with back analysis based on the other methods, because of the inherent complexity of the M-P method itself. The first part of the paper presents a way to determine the c-tanφ relationship for the M-P method. Subsequently, two procedures are given to obtain trial slip surfaces. By combining each of these trial slip surfaces with the c-tanφ relationship, an extremely limited range within which the unknown parameters, c and φ, should exist, is obtained. Application of this method to a fictitious and a practical problem indicates that the proposed method provides accurate and reliable strength parameters.

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This paper describes the behavior of ground anchorages installed in multi-layered strata under tensile load. It also shows a predicting method of load-displacement and load distribution curves derived from specific differential equations. Displacement and load distribution of anchors computed by the predicting method were compared with the results obtained from pull-out tests of actual anchors installed in a Kanto-loam stratum. There were good agreements between the computed and the observed load-displacement and load distribution curves.
In the end, this paper shows soil constants for the predicting method obtained from pull-out tests at 30 sites, and results of a numerical simulation for a model ground consisting of two strata.

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To investigate the quantitative applicability of the distinct element method (DEM) to stress-strain behavior of granular materials, direct shear box tests and biaxial compression tests on granular assemblies of aluminium rods are compared with DEM. And using the analytical results, the stress ratio versus strain increment ratio relation on the “mobilized plane” is investigated from the microscopic points of view. The conclusions can be summarized in the followings. (1) DEM can be a useful tool for research into the microscopic mechanism of the behavior of granular materials. (2) On the “mobilized plane”, the stress ratio and the strain increment ratio can be linked respectively through the average value of interparticle contact angle and the stress ratio can be linearly related to the strain increment ratio.

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A deep vertical shaft down to 50m and a relatively large-diameter tunnel were excavated in a sedimentary mudstone deposit for research purposes. The deformation characteristics of sedimentary soft rock was studied from field observations and their back-analysis taking into account the initial stress state estimated by the over-coring method. The Young's modulus from the field behavior was very similar to that obtained by various in-situ tests and the triaxial tests when the strain level-dependency of stiffness and shear stress-dependency of that evaluated by the triaxial compression tests are considered. Therefore, in this mudstone deposit, the effects of cracks, joints, faults and the confining pressure are insignificant.

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To explicate how the grain shape of sand can influence its isotropic consolidation and shear characteristics, an isotropic consolidation test, a drained triaxial test and a cyclic undrained triaxial test had been carried out on materials whose particle size and grain size distribution are the same but grain shapes are different. From these tests it appeared that the shape differences have a great influenceon the angle of internal friction, the dilatancy characteristics, and the liquefaction resistance; and that the compression index when the sand is isotropically consolidated is uniquely determined by the initial void ratio, and the modulus of deformation indicating the rigidity in the early stage of the shearing by the volume decrease potential.

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On the basis of σ_m-constant plane strain test results, a double-hardening elasto-plastic model is proposed. An associated flow rule is employed for plastic compressive strain, and a non-associated flow rule for plastic shear strain. The failure criterion, yielding function and work-hardening parameter are discussed. Applying the model to σ₃-constant plane strain condition, the predicted results showed good agreement with the test results. The same procedure of modeling is also carried out for a series of triaxial compression tests and the same conclusion is obtained. Finally, by comparing the parameters obtained from the triaxial and plane strain tests noted above, the generalization and extension of the model is discussed.

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Three loading tests of square footing (0.2, 0.3, 0.4m) were conducted in a pneumatic caisson being constructed 8.7m below the ground surface on a sandy layer containing cobbles, of which cohesive intercept was estimated to be 1kN/m² from triaxial compression tests and field direct tension tests. After the loading tests, visible shear bands were observed. A detailed examination of the shear bands by X-ray radiograph and magnified photograph reveals that the shear bands beneath the footing under high pressure were formed with densification by particle crushing, whereas the shear bands in passive zones under small pressure were loosen by positive dilatancy.

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In analyzing the deformation of soft ground, it is necessary to estimate the in-situ effective stresses before the construction works through the careful examination of the fluctuation of water table and reclamation history on the ground. A mehtod using one dimensional finite element method is proposed to estimate the distribution of the water pressure in the ground. This method is applied to four construction sites and is examined by comparing calculated values with monitored the ground behaviour.

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This paper describes the mobilization mechanism of vane shear strength revealed in the naturally consolidated clay deposits. The vane shear test has been successfully simulated by the 3-dimensional soil/water coupling finite element program, DACSAR, and through this numerical analysis the mobilization mechanism of vane shear strength has been explained. After verifying the finite element modelling, discussed are, mainly, the development of shear stresses along the blade of vane, their distribution, the effects of partial drainage and material viscosity. The in-situ vane shear test hardly escapes from much influence both of partial drainage and material viscosity. In particular, the partial drainage of pore water yields the difference between strengths at the top and/or bottom edges of a vane blade and at the side edge of a vane blade.

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The behavior of an exciter which vibrates on the ground is studied through a numerical simulation. Results of the simulation make it clear that the vibrating behavior of an exciter varies not only with the stiffness of the ground, but also with the mechanical factors of the exciter, such as weight, frequency, etc. The effects of those factors on the behavior of a exciter are arranged with the resonant frequency of the exciter-ground system. The results of the arrangement yield a figure on which the ground stiffness can be uniquely specified from the vibrating behavior and the mechanical factors of the exciter. In this paper, we suggest a developing method with which the degree of soil compaction can easily be measured from the vibrating behavior of any exciter using this figure. The application of this method was examined in some model and field experiments.

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To investigate the validity of an automated grain size analysis equipment for soil samples, X-ray method analyses were carried out on five soils. The JIS and laser method analyses were also performed on the three soils to evaluate the reliability of the results obtained by the X-ray method. It was found that the X-ray method showed significantly more accurate results than those which were obtained by laser and JIS methods. It was confirmed that the main advantages of the X-ray method are its simplicity, repeatability, reliability, and speedy in engineering practice. In addition, it provides added advantages of fully-automated operation for grain size analysis control and analysis data management and also ability to correct measured fine content (clay fraction) omitting human factors.

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Two types of centrifuges exist in geotechnical model tests: beam centrifuge and drum centrifuge. The authors have designed, constructed and utilized two samll diameter drum centrifuges since 1985. They have examined the applicability of the drum centrifuges to geotechnical model testing, including problems of self-weight consolidation, liquefaction, behaviour of buried piles during earthquakes. This report summarizes their five years experiences and discusses the potential use of the drum centrifuge.

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Effects of some protection methods against frost actions were experimentally studied. A filter layer of gravel or permeable thermal insulating material was set in the field test basins which were filled with frost susceptible soil. The filter layer used in this study can prevent capillary rise and permit seepage water downward. The amount of frost heave, frost heaving force, depth of freezing front and water transfer were measured during winter.
The main results of these experiments were as follows:
1) The amount of frost heave at the ground which has a filter layer of gravel or permeable thermal insulating material was about one-half or one-third of that at the untreated ground.
2) Bothh gravel layer and thermal insulating layer could cut off capillary rise completely.
3) When permeable thermal insulating material was used, the freezing front would be stopped in the filter layer.

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When excavating shallow tunnels in ground consisting of granular materials like sands, both surface subsidence, due to loosening of the ground, and earth pressure acting on a tunnel lining, become serious problems. In order to solve these problems, model tests have been conducted in the laboratory by using a group of alminum bars, in which a circular hole is made as a model of a tunnel. In the tests, a new piece of equipment has been developed, which can apply air pressure on the internal surface of the hole. The air pressure is then gradually reduced from a certain level to represent an excavation operation of tunnels. Thus, it enables to us to determine the minimum pressure necessary to stabilize the hole. The experimental results discussed in comparison with those obtained by a conventional method, applying constant displacement all over the internal surface of a tunnel.

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This paper proposes a method for improving the accuracy of ground displacement measurements by using the Global Positioning System (GPS). Adaptive filtering was adopted to formulate the method. Numerical simulations were conducted in order to prove the applicability of the method to GPS displacement measurements.

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