The analysis of the interaction between a circular tunnel lining and the surrounding saturated poroelastic soil is presented by use of the exact theory for the treatment of the lining. The method of analysis is performed by Laplace Transforms of the governing equations with respect to time and by numerical inversions of them. A parametric study is carried out to investigate the effects of the elastic properties of both the lining and the soil, the thickness of the lining, and the magnitude of applied initial stress states of the soil upon the behaviour of the lining. The comparison between the exact theory due to the Authors and the shell theory for the treatment of the lining is made by numerical results and graphical representations.

抄録全体を表示

In this study, the analysis of the absorbing conditions of hysteresis energy of soil was made. The hysteresis energy is calculated using the results of numerical analysis and on-line earthquake response loading test. Especially, the effect of the characteristics of the input acceleration wave is considered.
As the analytical results, the following conclusions were obtained; when an input wave is narrow-banded wave that have one predominant component, the hysteresis energy is largest. And, in wide-banded wave, the hysteresis energy is very small.

抄録全体を表示

A method is presented for predicting e-logp curve and logc_v-logp curve of a given soft soil from its natural water content, without making a consolidation test. The method, where an equation is used to predict e-logp curve and logc_v-logp curve, has been derived from the statistical analysis of the results of conventional oedometer tests on total 287 undisturbed samples containing venous types of soils such as ordinary clays, silty soils, organic soils and peat soils. Natural water content of these samples ranged from about 25% to 1000%. Good agreements can be seen between measured curves in the laboratory and predicted ones obtained from the proposed method.

抄録全体を表示

In surveying the permeability of dam foundations, Lugeon water test is usually adopted and the permeability is evaluated by Lugeon value (Lu). The curve between pressure and rate of water injection (p-q curve) is drawn by using the test results and Lugeon value is obtained from the slope of straight line part of p-q curve. However, quite a few p-q curves which have various shapes except the straight line, are obtained when Lugeon water tests are performed at fields. Therefore, in order to interpret the results of Lugeon water tests accurately the authors performs the following things: (1) p-q curves obtained from Lugeon water tests are classified into several categories, (2) causes of several p-q curves classified in (1) are summarized, (3) the methods to determine the accurate Lugeon value from each p-q curve are illustrated.

抄録全体を表示

Discontinuities have been investigated for years to determine actual rock mass behavior. However, data aquisition of discontinuity (joint) network displayed on the rock mass is not easy task. This paper describes an image processing method that will greatly facilitate this kind of job. Instead of land surveying and subsequent drafting of the joint map, this image processing system deals with photographs of a rock surface and produces a joint map easily. Fractal theory was introduced to quantify the complexity of the joint maps and it is extended to measure joint surface roughness.

抄録全体を表示

A mathematical model is presented for mass transport in fracture networks. The model is based on particle tracking method and is capable of simulating interactions between rock matrix and fractures. An analytical solution of advective transport equation considering matrix diffusion is used as a probability density function to determine the travel time of particles in each fracture element. By applying the model to some test problems and comparing results with an analytical solution and a solution by finite element method, the proposed model is found to have enough accuracy and reliability. In order to examine the effect of matrix diffusion on mass transport, fracture networks are generated stochastically. The result shows that matrix diffusion has less retardation effect as the distribution of fracture apertures becomes wider.

抄録全体を表示

According to present designing practice for soil-supported structures, superstructure and foundation are separately considered. This design procedure may lead to number of engineering and economical disadvantageous. This paper is discussed optimization of soil-supported structures considering superstructure and foundation as a system. In the developing of this method, load deformation relationship for both vertical and horizontal directions are considered. For the optimum system, the expected total cost is considered among various optional system designs. A case of soil-supported bridge structure on a piled foundation is also discussed using the proposed method and the optimum safety factor for the system are selected based on system reliability.

抄録全体を表示

The coefficients of earth pressure of dry sand C₀ and C′₀ was obtained by means of cyclic shear tests using Kjellman's type simple shear test apparatus fixed on a shaking table. C₀ was defined by the ratio of horizontal stresses to vertical stresses, developed in sand during cyclic shear, and C′₀ the ratio of minor or intermediate principal stress to major principal stresses. It was found that C₀ and C′₀ increased with increasing the horizontal seismic coefficient k_h, and C₀ in shear direction was 1.2-1.5 times as large as C₀ in the direction perpendicular to that up to k_h=0.4. It was also found that the internal friction angle of sand φ′ decreased by 2.5° with increasing k_h by 0.1.
For the case of liquefaction tests on saturated sand, the variations of C₀ and C′₀ with number of cycles were presented.

抄録全体を表示

To investigate the dilatancy characteristics of normally consolidated cohesive soils, isotropically consolidated triaxial compression test with mean effective principal stress equal to constant (CIPCC) was performed on two soils. As a consequence, the time dependency on volumetric and shear strain rates was shown. In conventional laboratory triaxial testing, on the other hand, isotropically consolidated triaxial compression tests (CIUC) primarily are conducted because of convenience and simplicity of testing procedures. Comparison of CIUC and CIPCC test results suggest that the dilatancy characteristics from the CIPCC could be extrapolated from results obtained on CIUC test.

抄録全体を表示

The paper explains the phenomenon that the dynamic moduli of cohesive soil consolidated anisotropically depend on the strain history, through a series of triaxial vibration tests. First, by the deduction of constitutive relation for drained shear of clay, it is concluded that the difference of strain history between isotropic and anisotropic consolidation causes the characteristics of mechanical behavior of each soil. Then, the undrained vibratory test with the strain level of 10^-4 indicates that the dynamic rigidity of K₀-consolidated clays is as high as 1.5 times that of isotropically consolidated ones. The dependency of the dynamic rigidity on the confined stress and the void ratio is also investigated using the test results.

抄録全体を表示

In the consolidated undrained test on cohesive soils, consolidation duration influences on the undrained shear behavior. Consequently, appropriate criterion for judging end of consolidation is required.
In order to study the applicability of the square root time fitting method and the usefulness of 3t method (JSSMFE, 1979) to determine consolidation duration, a series of consolidated undrained triaxial compression test with different consolidation duration on four normally consolidated cohesive soils was performed. Based on the test results, it was shown that the square root time fitting method can be applicable to triaxial isotropic consolidation, but 3t method is better to minimize the influence of consolidation duration on the stress-strain-strength behavior of cohesive soil during undrained shear process.

抄録全体を表示

In this paper, the method to identify unsaturated soil hydraulic properties which allows for hysteresis in the retention function is investigated in inverse problem. This study proposes a new method to determine the main drying and wetting curve from observed values of the main drying curve and from those of the scanning curve in wetting process. Especially, the importance of the selecting observed values of water contents or heads is emphasized, and the reasonable phases for observing is clearly shown by the sensitivity analysis. The applicability of the proposed method to the simple model and the observed model is estimated.

抄録全体を表示

In this paper, the results of tests on various kinds of in-situ piles are summarized, and the following knowledge has been obtained regarding the evaluation methods of the uplift resistance of transmission tower foundations: (1) The majority of the uplift resistance of piles is borne by the skin friction. (2) When the skin friction of steel pipe displacement and non-displacement piles in sandy soil are compared, the friction of the former is greater than that of the latter. However, there is observed to be no significant difference in the skin friction of both of them in soft clayey soil. (3) The maximum skin friction is evaluated to be f_s=1/5N (≤10tf/m²) for sand and f_c=N(≤3tf/m²) for clayey soil. (4) Where the allowable bearing capacity is 1/3 of the Ultimate Capacity, any hazardous effect will not be caused on the superstructure.

抄録全体を表示

Actual earthquakes generate complicated patterns of motions involving changes not only in amplitude but also in direction. In order to investigate the behavior under irregular pattern of shearing, several series of multi-directional drained simple shear tests on Toyoura sand were conducted by means of a simple shear test device incorporating two cyclic loading apparatus in two mutually perpendicular horizontal directions. Cumulative shear strain G and resultant shear strain Γ were introduced to find a unified law for dilatancy. And it was found that there exists a unique relationship between G and volumetric strains with a parameter of Γ independent of the shear strain history. Based on the arrangements of the test results, we find that the bowl-shaped slope, which compresses in accordance with G, exists in the strain space.

抄録全体を表示

In order to determine the optimum executive conditions of the primary lining constructed in a time dependent soft rock tunnel, a theoretical method has been proposed. In this method, earth pressure, displacements and axial stresses of supports and shotcrete are calculated, and in which such factors are taken into account as (1) viscoelastic behavior of the ground, (2) advancing velocity of the tunnel face, (3) time dependency of the modulus of elasticity and the strength of the shotcrete, (4) elastoplastic behavior of the lining, (5) executive conditions of the lining.
By appling the method to the highly time dependent ground, good applicability of the method has been shown through the comparison of analytical and field measurement results on earth pressure.
Some considerations on reasonable executive conditions of the primary lining are given by performing parametric study.

抄録全体を表示

An attempt is made to interpret the strain measured along a strain-pipe embedded in landslide areas with the aid of a continuous curve fitting by cubic spline functions. The aim of the present research is to identify the slip planes in the particular areas as well as to evaluate the current extent of the sliding movement.
The strain-pipe employed is made of a plastic material with strain gauges attached on its side wall. The pipe is penetrated into stable layers beneath a slope so that the bottom tip is fixed.
The pipe is modeled as a beam lying on an elastic foundation. The theory of beams suggests that the strain measured by gauges are proportional to the bending moment whose first-order derivative is equal to the shear force. The maximum shear force is expected to occur at an elevation close to the slip plane. Furthermore, the lateral displacement of the pipe and surrounding soils can be evaluated by integrating the moment twice along the pipe.
The method described above was used for two case studies at the Er-Jen Mountain and the Lung-Tan District. By comparing the results with those of the limit equilibrium analyses, it was found that both strain-pipe and numerical methods gave very similar locations of slip planes.

抄録全体を表示

The problem of elastic wave travelling in rock mass that usually contains cracks, involves several difficulties from the theoretical point of view. In this paper, a new model to treat such problems is proposed, in which, instead of modelling the cracks directly, the mechanical effects of cracks are transformed into an equivalent nodal force in a numerical procedure. Accordingly, the response is obtained by the superposition of the incident wave field and the scattering wave field which is produced by the radiation of the reflected waves from the crack surfaces. Finally, a numerical example is given and it is shown that the calculated results by the proposed method is in very good agreement with those of the exact ones.

抄録全体を表示

In order to analyze 3-D (three-dimensional) slope stability, a new 3-D slice method is proposed by extending 2-D Spencer's method. This method is applicable to the case of non-circular slip surface and satisfies moment equilibrium and vertical and horizontal force equilibrium for sliding mass. Two examples of calculation are presented to show the accuracy of the method and comparatively large 3-D effect in a practical case.

抄録全体を表示

Numerous methods of three-dimensional (3-D) stability analysis have been proposed based on the limit equilibrium by the use of a cylindrical slip surface with various shape of caps. Herein we consider the mechanism that produces the 3-D effects by a variational stability analysis, in which a log-spiral slip surface is provided. From the numerical results, it is shown that 3-D effects are caused on account of the soil mass not moving to the steepest direction on the slip surface for a moderate slope of small friction, while 3-D effects are caused mainly by the end-effects for a steep slope of frictional material. It is noticed that 3-D effects fail to be evaluated properly by the cylindrical surface for a moderate slope with small friction.

抄録全体を表示

Present study describes a new method of back calculation of the shear strength adaptable to a heterogeneous slope as well as homogeneous one. Proposed is an iterative method of the variational stability analysis, in which friction-dependent slip lines expressed by some log-spirals are provided. Therefore cohesion and friction angle are determined independently, especially the latter is particulated every different zone. After the verification of the method by the stability analysis results, the effects of the errors of the safety factor or location of the slip line specified as input data of the back analysis on the calculated strength are also examined. Finally the method is shown to be effective by applying it to a problem reported by other researcher.

抄録全体を表示