In this paper, the authors deal with the correlation between the releasing stress level on the preceded stress-strain diagram and acoustic emission (AE) under the repetitional loading. Models of soft and hard rock were made with cement mortar and the specimens were loaded by a stiff testing machine. The AE count rate, the mean square of amplitude and the frequency of AE wave were employed as the AE parameter.
It was clarified that the point of inflection in the increasing section of the AE count rate curve corresponds with the maximum hysteresis strain at the pre-loading, and the region included the releasing point on the stress-strain curve can ascertain with the position of the peak on the AE count rate curve. Based on the above test results, a new estimating method of initial geo-stress was suggested.

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We studied about the input parameters of supports and grounds for the tunnel design program reported in previous proceedings, 346/III-1. Creep tests of shotcrete in early stage of less than 1 week were done to decide equivalent modulus of elasticity. Tensile tests about ordinary bar and twisted bar clarified their characteristics, from which we find it appropriate to use the former for general tunnels and the latter for large deformation tunnel. Parameter studies of ground have been made comparing the measured and the calculated values of 12 tunnels, and therefrom it appears that initial lateral coefficient K₀ is strongly correlated to overburden H. Modification factor to modulus of elasticity was thus obtained for each class of ground.

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Until now, the quasi-three dimensional groundwater flow analysis has been used for many kinds of groundwater simulations in this country. However, to apply its computation method to the groundwater flow analysis for the tunnel and cavern in fractured rock masses is not available, because the discharges of both tunnel and cavern are unknown beforehand. In this paper, the authors proposed a new FEM technique for analyzing the flow around tunnel and cavern in fractured rock ground. The groundwater model is composed of some fractures and weathered layer on the rock ground, and the model can be applied to analyze the flow in both saturated and unsaturated aquifers under the assumption that the flow in weathered layer is subjected to the Dupuit's approximation.

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Due to development of injection technique and grouting materials, injection zone of grout became more homogeneous than before. Therefore, it has been possible for designing to utilize theoretical soil mechanics insteed of a judgement on the basis of experience. In addition, the advance of computer results in easy mathematic analyses. Accordingly, it is necessary to have the unifieded failure criterion in the region of tension and compression. For that reason, in this study, the strength properties of grouted sand were examined. As a result, criterion of failure was explained with octahedral stress. This failure criterion is also useful to evaluate the efficiency of injection.

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The mechanical behavior of saturated model rock mass with a clayey seam was investigated by conducting a series of undrained triaxial compression tests. In the tests, a rock mass was modeled by a specimen made by sandwiching an alluvial clay seam between two pieces of Ohya-stone (tuff). The effects of the thickness of clayey seam, the inclination of seam plane to the maximum principal stress direction, the shear strain rate, the confining pressure and the over-consolidation ratio on the mechanical behavior of rock mass were studied based on the effective strees concept. From the experimental results, even if the thickness of clayey seam was so thin, the shear strength of rock mass is found to be governed by that of the clayey seam.

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Dynamic modulus of rigidity and damping coefficient of sandy soils under low confining pressures (less than around 20kPa) were investigated in the present study. Series of cyclic simple shear tests in which horizontal inertia force is applied on the surface of the specimen by use of a shaking table apparatus were performed on Toyoura sand and a compacted sandy soil. Some features associated with deformation parameters such as their dependencies on confining pressure and shear strain amplitude were examined, and the results were compared with those of cyclic triaxial and torsional shear tests conducted under routine high confining pressures in order to discuss characteristic differences and correlation between parameters obtained in low and high stress ranges.

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The contact tensor and modified stress tensor for granular materials are proposed in order to account for the internal fabric state and internal stress state. The fundamental features of these tensors are discussed and the evolutions of them for monotonic and cyclic loadings are examined. The significance of them as internal variables for the description of mechanical behavior of granular materials is discussed. The simple kinematics of granular materials is proposed and the dilatant behavior is discussed. The spin tensor, which has been neglected in the kinematics of granular materials, is also studied.

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As an important problem of construction machinery, it is necessary to study the boundary region of mechanical properties between metal and rock mass to get a rational maintenance of rock excavating tip. Here, the amount of wear and wear length of pure rippertip and hard surfaced one by means of spraying or welding were measured respectively at several different ripping operation sites of land reclamation. It was clarified that the amount of wear of pure tip is fairly correlated to the index of rock mass strength for wear, and the wear resistance and self-sharpness of tip coated by carbide composite welded metal presents to be higher than the other metals. And also, the effect of hardfacing of sprayed metal can not present under high contact pressure, but develops considerably under low pressure.

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In this research, upward seepage flow tests and analysis have been performed for the model ground with or without a sigle pile, in order to investigate the effects of gravel piles on the stability of surface soil against so-called secondary liquefaction. The results calculated by analytical procedure are in good agreement with the experimental results for every case tested in this research. Finally, authors estimated the effects of gravel piles against secondary liquefaction by calculating bearing capacity of the improved ground considering excess pore pressure in the ground.

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In order to know the Kaiser effect of AE (Acoustic Emission) in triaxial directions of a rock mass, the Kaiser effect of AE in the granite specimens were investigated by applying the compressive pre-stresses of various intensities repeatedly on the respective directions to the specimens.
From the testing results, it was found that the pre-compressed principal stresses were precisely estimated by the Kaiser effect, provided the specimens had been repeatedly pre-compressed until the increment of the residual strain ceased.

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Effects of undrained cyclic stress-strain history on clay behavior were studied by cyclic triaxial compression tests. An apparently-overconsolidated clay produced by undrained cyclic loading decreases its undrained strength because of the decrease in effective stress in clay. while a clay subjected to drained cyclic loading gains the strength similarly to the long-termed consolidated clay. Undrained strengths of a reconstituted marine soft clay were predicted by a method which was formerly extended from the empirical relation existing between overconsolidated and normally-consolidated clays. In terms of the effective stress analysis, the critical state parameter in clay has nothing to do with undrained cyclic loading histories.

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The quasi-overconsolidation characteristics of a so-called aged normally consolidated clay are considered from the viewpoint of change in state during the secondary compression, in order to explain the mechanism of variation in stress and strain under the condition of 1-D compression. Especially, it is shown that the difference of time-dependency between the dilatancy and the distortional creep discriminates the pattern of change in state, through a series of the drained creep test and the long-term consolidation test using kaolin. As an approximate approach for analyzing such behaviors peculiar to the cohesive soil, a three-dimensional dilatant visco-elastic model of clay is calculated quantitatively by means of Laplace transformation.

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A new preparation method of undisturbed specimen of decomposed granite soil by freezing a block sample is developed. Triaxial and simple shear tests were carried out for undisturbed and compacted specimens. The following results are obtained.
1) The simple shear test results can give the strength parameters of the unsaturated and the saturated specimens at the low pressure. These parameters are valid for the analysis of a slope stability.
2) The relationships between stress, strain and volumetric strain on the undisturbed and compacted specimens are different. This fact, especially concerning the dilatancy characteristics of these samples, is explained by the distribution of pore size and crushing of the particles.
3) The suction in unsaturated specimen is important for the strength.

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Although the rockbolts are used very often as a main member of supports in NATM, the fact is that there are various understanding of the effects of rockbolts and that there has been no specified way of design. It is because the effects of rockbolts have been recognized mainly through experiences and also because there is no good way of investigation of them.
This study of rockbolts by two lowering panels is a method of examining more positively the mechanical properties of rockbolts presented by our authors, following the previous study by one lowering panel. This series of the experiments by two lowering panels were made to examine the mechanical properties of a group of rockbolts while the experiments by one lowering panel were made to examine the effects of a rockbolt.
This report describes the behavior of rockbolts found through the experiments of two lowering panels including theoretical consideration. And it also describes our view of design of rockbolts.

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This paper discusses stability analysis of inclined and inhomogeneous cohesive slopes with finite length. The method of analysis is based on three-dimensional limit equilibrium techniques and variational calculus. The three-dimensional stability factors were calculated as the functions of the ratio of failure length (perpendicular to cross section) to slope height, slope angle and factor of inhomogeneity. Based on these calculations the three-dimensional stability charts were presented. The solutions obtained here give the upper bounds of the problem in limit analysis.

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The purpose of the present paper is to propose a methodology of the seismic risk analysis of slopes and earth structures based on the seismic coefficient. First, attenuation study of peak acceleration for various earthquakes in Japan is made and this shows noticeable scatterness depending upon the region of the earthquake. Second, the records of about twenty thousands earthquakes which occured in Japan are investigated to determine the area of “earthquake nest” and Gutenberg-Richter's equation is given for each “earthquake nest.” These results are incorporated with the seismic risk analysis assuming the circular seismic source and poisson process as a seismic source model. The actual cases are analysed by the proposed method and they show the validity of the method to distinguish the failure case and non-failure case.

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The sand compaction piles are often applied in order to improve a poor ground in Japan. The very soft clay layer under a sea inevitably heaves by driving the sand compaction piles in the ground. Since the removal of an upheaved part brings a high cost and a muddy water, it is strongly demanded to utilize the upheaved part as a foundation of structures. This paper discribes the results of a proto-type field test in a sea. The generating mechanism of the upheaved ground and its shape by the sand compaction piles are shown with the soil properties. The shear strength of the upheaved ground increases with the effect of the sand piles for drain wells. The deformation characteristics and stability of the upheaved ground are investigated by a field loading test. The loading control method to construct the structure safely on the upheaved ground is also proposed.

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A superstructure and a substructure are designed separately in the general design method, since an interaction between them is very complicated. The present paper proposes a procedure of optimization for system reliability of a soil-supported structure as one system. A plate girder bridge is taken up as an example of a structure. Ununiform settlement between an abutment and a pier which is generated by consolidation of a clay layer influences on the degree of safety of a main girder. Under such a condition, the optimum safety factors of a main girder and an abutment are investigated with some numerical examples. The optimum safety factors obtained are close to those given in the current design specifications.

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Both vertical and horizontal samples of undisturbed fibrous peats, which were obtained by maintaining the axes of thin-walled tubes parallel to the vertical and horizontal directions in the peat ground, were used. These samples contained the amount of organic matters more than 70%. A series of the undrained triaxial compression and extension tests with pore water pressure measurement were performed on the specimens which were normally consolidated and overconsolidated under an isotropic stress condition, and the influence of fabric anisotropy on undrained shear behavior of peats was investigated. Test results indicated that as the anisotropic fabric of fibrous peat which had formed during accumulation still remained after the end of isotropic consolidation, anisotropic shear behavior was observed remarkably.

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This paper discribes a probabilistic finite element method using the first-order approximation at a failure point of a set of random variables and the method is extended to the equivalent normal representation of nonnormal distributions. The method offers two advantages Firstly, the method will give a consistent measure of failure probability for the limit-states which are defined in terms of different but equivarent formulations of performance functions. Secondly, the method can be applied to the reliability analysis for nonnormal variates. Comparing the result of this method with that of Monte Carlo simulation, this method gives a satisfactory approximation. Furthermore an application of this method to the stability analysis of earth slope gives probability levels for a local failure and global failure on an assumed failure surface.

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A number of analytical tools are available for engineering calculations involving excavations. These include numerical methods, physical model techniques and limit equilibrium analysis. Block theory is new and it uses the stereographic projection. It can be applied to analyze the three dimensional system of joints and other rock discontinuities to find the critical blocks of the rock mass when excavated along defined surfaces. This paper describes the way to find key blocks in the systems of joint networks and to support them by bolting or other suppoting methods. For a severly jointed rock mass, an idea of a key block existing space which contains all key blocks in the excavated rock surface is proposed and it is used for determining the optimum support forces which stabilize such jointed rock mass.

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Bearing capacity due to plugged soil in an open-ended pipe pile is analysed. A mechanism of indentation of soil into the open-ended pipe pile is simplified making it easy to employ the deformation characteristics of soil in the analysis. The modelled plugging mechanism and the equilibrium of the plugged soil lead to an equation for bearing capacity due to the plugged soil. The validity of thus obtained equation is verified through a series of laboratory pile loading tests using a steel pipe pile penetrating a diatomaceous mudstone ground.

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In this paper, the correspondence was investigated between indoor compaction test and vibratory roller compaction as follows.
(1) From compaction results with various vibratory rollers, it was made clear that soil densities were determined by their dynamic line pressure.
(2) From impact compaction tests with various impact energies, it was ascertained that soil densities were determined by energy of rammer defined by the product of rammer weight and dropping height.
(3) The relationship between rammer energy and dynamic line pressure was investigated through the medium of densities obtained from (1), (2).
On the relationship obtained from (3), we suggested a new method for predicting the density of the field compacted soil from impact compaction test whose energy was changed according to respective vibratory rollers and its applicability was confirmed in field compaction.

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Japanese National Railways developed a new construction method of an underpass beneath the railway banking using a horizontal pipe jacking in 1976. But in earlier time, it was one of important problems to estimate its thrust when one wants to carry out this work. Thereafter, the author found that the thrust depends upon the characteristics of the ground, the shape of an element to be jacked, that of a cutter head and so on, proposed a formula to estimate this value and proved its practicability comparing the estimated value with that measured. The author also carried out the experiments to find out the effects of a few conventional methods to cut down the thrust on this construction method quantitatively and succeeded to enlarge the jacking length.

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The clay subjected to cyclic shear with drainage is in the state of quasi-overconsolidation. In order to investigate the characteristics of shear strength and of consolidation of quasi-overconsolidated clay, static shear tests and consolidation tests were carried out, using the simple shear test apparatus. Then, the results were compared with the ones for the overconsolidated clay. As a conclusion, it was clarified that quasi-overconsolidated clay induced by cyclic loading is affected with the disturbances of fabrics, comparing with the overconsolidated clay induced under static conditions.

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