This paper tries to examine the dynamic behavior of earth-structure as a ground with embankment during liquefaction and assess the effectiveness of the liquefaction countermeasures. From a total of six types of shaking table tests it can be seen that even for soft sandy ground liable to give rise to liquefaction in the surrounding horizontal ground parts, the excess pore water pressure of the foundation ground directly below the embankment did not reach the effective overburden stress and liquefaction did not occur. With a two-dimensional direct non-linear liquefaction program using effective stress analysis, it was possible to reproduce the measurement results obtained in the shaking table tests.

View full abstract

The vertical strain measurement in a rock mass was carried out by means of borehole strain gauges during progressive excavations of an underground powerhouse cavern, measuring 24m wide, 46.6m high and 134.5m long at 280m below the ground surface. Through the measurement, the following phenomena have been clarified, such as the irregular distribution of the compressive strain, the behavior of the strain increment at the loosened region, the effect of geological structure including discontinuities, and the effect of support system.

View full abstract

This paper describes displacement properties of rigid foundations on weathered rock by dynamic and static field tests, and comparisons the properties with theoritical and numercal computed solutions.
The contents are properties of bearing rock, relation between measured natural frequencies and computed eigenvalues, variability of resonance frequencies and complex rigidities in forced vibration tests, simulations of the forced vibration test by FEM, static response properties by repeated tests under large loading, and relation between dynamic and static properties. We think that obtained results are very useful for developments of seismic design methods.

View full abstract

In order to investigate on temperature effects of normally consolidated clay, consolidation tests under different temperature were carried out. It was clear that volume change of clay induced by heating is in proportion to increment of temperature change, while independent of consolidation pressure. Consolidation yield stress of clay is influenced on sort of clay and temperature change. From the above results, method for predicting yeild stess of clay subjected to temperature effects was proposed.

View full abstract

The water content of unsaturated soil does not always correspond to its suction, which results in the extream hysteresis loop of water characteristic curve. In this paper the influence of different water distribution on the compression behavior of unsaturated soil is examined. On this account, the influence on intergranular forces are examined based on a particle model, and added consideration are given to the effect of suction stress. The isotropic compression tests on spacimens of differnt water distribution under constant suctions were carried out, and the difference of volume change behavior and water content behavior between each spacimen were made clear.

View full abstract

The authors proposed an evaluating method in terms of the external work done to rock masses and the energy dissipated within rock masses, and showed the effectiveness of the method to evaluate the stability of rock masses without supports. This paper extended this method to be able to evaluate the stability of rock masses under the influence of internal pressure or rock volts. By the parametric model for the mechanical characteristics derived from shearing test data on rocks, the stability evaluation of soft rocks around tunnels under the inner pressure and the influence of the timing of support settings on the stability of rock masses were discussed.

View full abstract

With steel fiber reinforced concrete (SFRC) it was seen that the sectional force capacity becomes larger than that of plain concrete, because the tensile stress is transmitted through the steel fibers intersecting the crack surface even after cracking has developed. However there are almost no methods to calculate the sectional force capacity, with consideration of the tensile stress transmitted through the steel fibers. Therefore in this paper a method to calculate the sectional force capacity in SFRC is proposed based on fracture mechanics. To apply the method to SFRC tunnel linings the authors conducted test on a ring model and analyzed load-displacement curve of a ring model by nonlinear F.E.M. analysis.

View full abstract

In discontinuous rock mass whose behavior is mainly controlled by joints, it is the most important concern for us to find potentially unstable rock blocks. The block theory can determine a number of unstable blocks in the rock system, if the mechanical properties of joints are known. However, the strength parameters of rock joints are very often dispersive. In this paper, an attempt is made to analyze the stability of tetrahedral block by probabilistic approach. Application of performance function to a plane sliding failure mode and a wedge sliding failure mode was discussed by using the first order second moment method. It was also discussed how we can reduce the probability of failure within a certain range for the critical block by using a support system.

View full abstract

This paper is concerned with the estimation of permeability of an aquiclude clay layer in deep zone during construction of Trans-Tokyo Bay Highway and Kawasaki Manmade Island. The estimation was tried before and after construction of diaphragm walls.
First, the estimation of permeability of clay layer before the construction of the wall was simulated by pumping tests and Hantush's conventional t-s type curve method. Second, we estimated the permeability of clay layer after the construction of the wall by using ‘permeability estimation element’ in the model.

View full abstract

One-dimensional consolidation characteristics of undisturbed peat was examined in terms of the rate of settlement. From the test results, it was found that log settlement rate vs. log t relations were essentially composed of two portions of straight line. The measured slope of initial portion was smaller than that of theoretical value. From this fact, it was concluded that the settlement behavior of peat might not be explained by the Terzaghi theory. It was also found that if the slope of final portion is equal to -1, then the settlement occurs in proportion to log t. If its slope is not equal to -1, however, the coefficient of secondary compression decreases with time and settlement approaches to an ultimate value in an infinite time.

View full abstract

The dynamic elasto-plastic FEM is applied to analyse the difference of the behaviors of 2D and 3D slopes (end effects) during earthquakes. Simple homogeneous slopes are assumed to be subject to various simulated sine waves and two real earthquake motions. It is shown that the response of acceleration of slopes during earthquakes is reduced due to sliding, and the end effect gives much more influence on the slope stability in the dynamic case than in the static case.

View full abstract

A comparative study was made on the amount of the excessive pore water pressure produced during shield excavation and values of the current management items for various types of slurry. The result of the study revealed that current management item alone are not sufficient to evaluate the slurry properties. Then, we evaluated the slurry properties during shield excavation using the groutability ratio (GR). Our study has demonstrated that the excessive pore water pressure is minimized in the case of slurry having the GR value of 14 to 16, density of 1.20, fannel viscostiy of 25 to 30 second.

View full abstract

The testing method on the residual strength is not established. The residual strength of soils was obtained using the several shear test apparatus. The residual strength became smaller in the order of pre-cut triaxial test, reversal direct shear test, pre-cut direct shear test, simple shear type ring shear test and direct shear type ring shear test. The influences of restraint conditions and gravel fraction on residual strength were investigated. The residual strength of clayey soils by the simple shear type ring shear test was bigger than one by the direct shear type ring shear test. But the residual strength of the soil containing gravel showed the reverse tendency. This is due to the difference of the restraint condition of a slip surface.

View full abstract

The frame analysis is extensively used in designing of tunnel lining. In order to enable frame analysis of lining which involves cracking and its development, this paper proposes modeling and analytical procedures of plain concrete members. The proposed model and analytical scheme allowed us to conduct frame analysis capable of including cracking behavior, by assuming pin connection or rotating spring at nodes where a crack occurs. In addition, the effectiveness of proposed technique was verified by comparison with results of experiments using tunnel models and those of finite-element analysis based on the failure mechanics of concrete.

View full abstract

Known liquefaction sites were compared on the basis of survey results from ruins in Tokyo and of extant records for the historical earthquakes. The results have shown evidence to confirm that re-liquefaction has occurred. The properties of the liquefaction sites were assessed on the basis of topographical, geological and soil characteristics. The results indicate that the level of fines content in the alluvial deposit has a strong influence on the liquefaction. The results obtained from dynamic tests were evaluated to obtain the equation for the liquefaction resistance. An effective stress dynamic analysis has substantiated the usefulness of the characteristics in differentiating between re-liquefaction and non-liquefaction sites.

View full abstract

The dynamic strength by cyclic loading testing is compared with the static strength by monotonic loading testing using triaxial and torsional simple shear tests as for cyclic number, shear strength, relative density of specimen, confining pressure and initial shear stress. The results show that during an undrained cyclic loading test, the increase in the cyclic number is accompanied by rising axial strain and a rapid buildup of the porewater pressure to between 90% and 100%, but that liquefaction or flow failure does not occur. The cyclic shear stress ratio obtained from a torsional simple shear test is smaller than that obtained from a triaxial test, regardless of the mean principal stress or initial shear stress.

View full abstract

This paper presents model tests of heavy tamping focusing on the compacted area and strength increase by ram blows in the 100g centrifugal acceleration field in relation with the governing factors: ram mass, blow height and number of blows. The model materials are sandy soil passing the 2mm sieve. The compacted area is evaluated both by the increases of volumetric strain and cone penetration resistance. Main conclusions are: 1) the compacted area is governed by the total ram momentum rather than the total kinetic energy of the ram, 2) the depth and radius of the compacted area show linear relationships with the logarithm of the ram momentum, 3) the compacted area is not much influenced by the initial ground density and kind of soils used.

View full abstract

A series of monotonic and cyclic triaxial tests was performed on two decomposed granite soils and a volcanic soil “Shirasu” which are typical crushable soils in Japan. Both contractive and dilative monotonic shear behaviour were observed depending on the confining stress and initial relative density. The cyclic shear strengths were also dependent on the confining stress. The monotonic and cyclic shear behaviour were compared each other to find the mutual relationship. It was found that there is a unique relationship between the cyclic shear stress to cause liquefaction and the monotonic shear strength of phase transformation independent of the difference of soils, initial densities and confining stresses which is useful for estimating the cyclic strength by the static strength.

View full abstract

Disk cutters can excavate rock efficiently. But, the life of disk cutters are affected from the mounting position to the cutter head. Especially, the disk cutters installed at the center of cutter head are loaded by irregular force which induces the short life of disk cutters. In this paper, the acting forces are cleared near by center position of TBM. The experiment were carried out using the artificial rock models in order to keep the experiment conditions. The independent rotary type cutter with two disks is more suitable than the one body cutter with three disks.

View full abstract

It has been pointed out that the maximum depth of the Plastic Board Drain (PD), which is used for accelerating the dissipation of the pore water pressure in soft clay, is about 20m because of the small sectional area and low rigidity. The authors have developed the cross shaped drain (CSD) in order to be applied for the improvement of deeper soil. This cross shaped drain is composed of four band shaped drains, and the dissipation of pore water pressure is expected to be uniform. Triaxial K_o-consolidation tests were carried out. It was found that the equivalent diameter of CSD is about 1.5 times that of band shaped drain for the same width. A simple analytical method to estimate the equivalent diameter has been proposed.

View full abstract

The vibrating behavior of a vibratory roller was discussed through numerical simulation as a part of the development research of the ground evaluating system in which the ground stiffness can be evaluated in real-time by monitoring the vibrating behavior of a vibratory roller which depends on the ground stiffness in soil compaction. In the simulation, the vibratory roller-ground system was replaced by the second degree of freedom vibrating model and the reason its vibrating behavior changes according to the ground stiffness and its characteristics were discussed in detail by introducing the consideration of the nonlinear vibration and chaos.

View full abstract

Liner system used in waste landfill has tendency to be built as composite of geosynthetics like geomembranes and geotextiles. When it is used on side slope, driving forces from cover soil and/or vehicle create draw down of liner. In order to develop a practical procedure by which tensile force carried by each layer can be estimated, 4-layered shearing tests were conducted. As a result, it was found that the 2nd layer could create tensile force even when a frictional coefficient on the top interface was equal to that on the bottom interface. Based on theory of elasticity, an iteration procedure estimating tensile force is also proposed which considers relative displacement between components of layers.

View full abstract

This paper describes the mechanical properties of light-weight soil which were improved using cement and foam. Especially, failure criterion of light-weight soil, the influence of unconfined compressive strength and initial void ratio on light-weight soil is studied.
From the results of these studies, it is clear that the failure criterion should be described using q-p' relation and e-logp' relation. It was also learned that the unconfined compressive strength and initial void ratio of light-weight soil is influenced by slope failure of q-p' (M) line and e-logp' (Cc) line.

View full abstract

In the case of low temperature materials storage in openings excavated in rock mountain, such as LNG, LPG and frozen food etc., cracks occurs around openings by shrinkage of rock mass have been shown. Also in the cases a “water curtain system” and an “ice lining system” for countermeasure for preventing leakage of gas and liquid from the openings have been proposed. In this study, as another method a “resin lining system” was proposed, physical properties of resin at low temperature were obtained by the test. From the results of the stress analysis using these value, it was found that by the lining of resin make independent with rock, that is the “resin lining system” is an effective way to prevent leakage of gas and liquid from the openings.

View full abstract