The offshore expansion project of the Tokyo International Airport is to move toward an offshore land reclaimed by very soft clay, which was produced by dredging in the Tokyo Bay. Airport facilities such as a runway have very strict restriction on settlement for safe operation. To reduce residual settelments, various improvement methods were employed for large areas, considering soil conditions and type of strucutres. In addition, foundations of runways and aprons were designed, considering differential settlements caused by scatter in soil properties of the ground. These differential settlements were estimated by Monte-Carlo simulation.

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Based on the analysis of various in-situ measurement data collected during excavations of pumped-storage powerhouses located in deep ground, a concept that divides the excavation disturbed zones into plastic and non-plastic zones around underground openings is proposed in this study. A method to evaluate the excavation disturbed zones and the plastic zones based on measurement results of tangential stress and strain, radial interval strain, AE and joint behavior is developed. The validation of the method is carried out using real measurement data from Kazunogawa powerhouse cavern. Finally, a comparitive study is performed by changing material properties in zones defined acording to the proposed concept, and approaches to determine the rock mass mechanical properties which can predict the rock mass deformation behavior reasonably well are discussed.

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Recently, construction of high and steep earth fills using a high water content-cohesive soils is a common practice. Because geocomposites which have sandwiched structure of woven fabric between non-woven fabric have over the tensile strength of geogrids of woven fabrics and also having the drainage effect of non-woven fabrics. However, current design methods of nonwoven fabric-reinforced earth fills have considered the drainage function only. This paper presents an experimental study on geocomposites-reinforced steep earth fills using Kanto Loam. Comparing both no-reinforced and geocomposites-reinforced earth fills varying consolidated times, the efficiencies of the geocomposites as drainage and reinforcing material have been judged.

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Many types of Flexible Membrane Liner (FML) made of HDPE, TPO, FPA, EPDM and soon are used as a component of a liner system in waste landfill. But the FML spread on the bottom may create a tensile strain when the bottom subsides partially. In this paper, the authors conducted trapped door tests to confirm the area of FML where it deformed and to find the distribution of tensile strain creating in it. They also measured the change of vertical pressure acting on the FML according to the settlement of the modeled base. Based on the experimental results, they presented modified non-linear elastic model to calculate the maximum tensile strain where the redistributed vertical pressure was considered. As the result, it was recommended that the allowable partial settlement of the FML is about 15cm and 25cm for HDPE FML and FPAFML, respectively

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Stress boundary has conventionally been used for the prediction of ground movement during shield tunneling in plain strain two-dimensional finite element analysis. In this study, based on excavated surface displacement boundary input, a ground displacement prediction method was proposed for shield tunneling. The results of the proposed method of 2D and 3D analysis were compared and evaluated with the field measurement. As a result, it was made clear that asymmetrical surrounding ground displacement during curve excavation was able to be simulated with the proposed method and it achieved more precise simulation than the conventional method by stress boundary input.

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It has been known that the mechanical behavior of rock mass strongly depends on these of discontinuities such as faults, fractures and joints. In the rock mechanics literature, several constitutive models to predict joint shear strength have been proposed focusing on effect of geometrical properties of the joint surface roughness. It is shown, however, that some of existing models have problems that these do not quantitatively reflect on geometrical properties. In our study, the statistical parameter related to the strength properties obtained from the results of the direct shear experiments is introduced and a new constitutive model to predict shear strength of rock joint is proposed.

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Geomembrane sheets come to be commonly used for liners in waste landfill and are subjected to many kind of long term loads, and their function must be kept the sufficient safety during their serviceable term. In this study, creep characteristics of geomembrane made from High Density Poly Ethylene (HDPE) were experimentally investigated with considering the condition that the embedded geomembrane liners are subjected to differential settlement in base ground of waste landfill. The creep characteristics equation for soil material was applied to geomembrane materials to estimate their long term strength Furthermore, the decreased factor in tensile strength of geomembrane liner due to creep deformation is proposed for actual design.

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During the 2000 Tottori ken Seibu earthquake liquefaction failures occurred in reclaimed land at several locations. For reclaimed land in the Miho Bay area most of the liquefaction boils typically consisted of very fine soil. Samples were taken both from liquefaction boils on the surface and from boreholes sunk in the Takenouchi industrial zone and behind the quay wall in Showamachi. Using these samples comparisons were made between the characteristics of these various soils in order to identify the liquefaction layer in the ground. Current design specifications do not recognise fine material as liquefiable. However this study showed that it is important to consider the nature of the fines including the clay content and plasticity before excluding the possibility of liquefaction.

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A jacket-type steel-pile foundation has a feature that it can reduce the load acting on the piles drastically because the foundation and the superstructure are connected continuously by the jacket that is much lighter than a conventional top-heavy foundation. Moreover, if inclined piles are properly used as a pile foundation, it is possible to increase efficiently the lateral resistance and the rigidity of the foundation. In this paper, the lateral resistance and the failure mechanism of a group-pile foundation with inclined piles by centrifuge model tests, the influence of the pile spacing and the inclined angle of the piles on the lateral resistance were analyzed by 3-D finite element analysis.

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Loose saturated sand behaves as a solid before liquefaction but as a fluid when the excess pore water pressure equals the initial confining stress, after which it recovers strength. In this paper, a simple constitutive equation for saturated loose sand was developed to express the phase transformation phenomenon between solid and fluid during liquefaction and the ground flow phenomenon. This is named the fluidal elasto-plastic constitutive equation, which combines a cyclic elasto-plastic behavior of sand and Newtonian viscous fluid characteristic of liquefied sand by defining a state controlling function. This constitutive equation was used for the shaking table test, and its applicability investigated by comparing numerical and experimental results.

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A series of centrifuge model tests and numerical analyses were carried out to investigate vertical bearing capacity of embedded foundation in a clay ground whose undrained shear strength increases with depth. The embedded depth and the width of the foundation are changed in the model tests to study these effects on the bearing capacity. It is found that the bearing capacity increases almost linearly with increasing the ratio of embedded depth and width of the foun-dation. A series of stress characteristic analyses was also carried out to investigate the effects of ground strength dis-tribution with the depth, and ratio of the embedded depth and width of the foundation on the bearing capacity. It was found that the measured vertical bearing capacities were well coincided with those of calculation.

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A sand sample erupted by liquefaction is one of the keys to estimate the grain size distribution of liquefiable soils. When the sampling of erupted sand is appropriately performed, the erupted sand can provide substantial information on liquefied layers. Moreover, since such a sample is easily obtainable from the liquefied site, reasonable evaluation of the liquefiable grain size distribution based on a large number of samples is possible. In this study, using 823 samples obtained from liquefied sites due to 13 earthquakes, the following aspects were examined: 1) the difference in grain size distribution between samples taken from young aged grounds (e. g., reclaimed lands), and samples taken from grounds composed mainly of Holocene deposits; 2) the properties of grain size distributions of the erupted sands; and 3) comparison with the conventional criteria of grain size distribution of liquefiable soil. It was found that there exist finer limits in the grain size distribution of liquefiable soils for young aged ground and Holocene deposits, respectively.

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The simplified model for weak rock tunnel is developed based on perfectly elasto-plastic concepts considering the effect of support pressure due to rockbolting with bearing plate. The model is verified by model tests in which we adopt axisymmetrical tunnel models with various bolting pattern (bolt length and circumferential and longitudinal bolt spacing) in artificial ground modeled on weak rock. The model proposed in this paper could be estimated the optimum bolt length and bolting pattern based on the allowable displacement of tunnel wall. The results of a series of test indicate that: i) the shear stress along the bolt acted as anchor length if the bearing plate set at the tunnel wall; ii) the support effect increased with the decrease of bolt spacing rather than bolt length within the test cases.

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Proposed is a nonlinear earthquake response analysis in frequency domain. Stress-strain relations in frequency domain are defined by the vector spectrum method, i. e., Fourier transforms of stress and strain in a complex plane, and relationships between stress-strain behavior in frequency domain and actual stress-strain curve are investigated. Frequency range where response of subsoil is affected strongly by the nonlinear behavior is evaluated by comparing the unsteady spectrum with a nonlinear effective function that is defined as the first derivative of an amplification factor with respect to a shear wave velocity. A method to evaluate effective strains in frequency domain from the maximum shear strain in time domain is proposed by combining above two findings. The proposed method is compared with conventional equivalent linear methods at two sites where strong motion vertical array records were obtained. The proposed method always shows better agreement with other methods.

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This paper describes chemical and physical properties of 15 weathered soils of the Sangun metamorphic rocks. Also, compaction and CBR characteristics of the soils are discussed in terms of applicability for filling material. Main conclusions are as follows. The Sangun metamorphic rocks mainly distributed in Yamaguchi prefecture are pelitic schist, basic schist and serpentinite. The finer and clay contents of the pelitic schist are lower than those of the basic schist and the serpentinite. Compaction tests on the pelitic schist showed a better result, compared with the others. There exists a good correlation between the maximum dry density, the contents of SiO₂ and Fe₂O₃, the finer content and the ignition loss, respectively. Because the modified CBR values of the soils are under about 7.5%, the cement stabilization is examined to utilize the soils as filling material.

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For studying non-stationary seismic ground response subjected to a strong earthquake motion, a new method is proposed. The method is time-frequency domain analysis using a fast wavelet transform, and non-stationary variation of shear stiffness and damping ratio are determined by dissipation energy and maximum shear strain amplitude. Most valuable point of the method is that the deterioration of shear stiffness can be obtained explicitly as a result of analysis. Applicability of the method to practical problem is studied by the case history of the seisimic array observation site of Kobe Port Island in the 1995 Kobe earthquake.

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Residual effective stress (σ_r) was measured for various soils, which were recovered from various sites in the world. As a result, it turns out that measured σ_r is considerably different among those sampled specimens.
Behavior of negative pore water pressure (u_w) is found to be dependent on c_v. Soils with large value of c_v, can't retain their suction for long time, while the soils with low c_v can retain u_w for relatively longer time. It has been found that σ_r of samples obtained from different areas are influenced by their depositional environments.

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Rock is often considerably anisotropic. But it may be said that there has been no practical method of measuring it in the scale matching the insitu tests. The features of the newly developed method are that, 1) it requires only one hollow cylinder specimen to obtain a set of orthotropic anisotropy, 2) it does not require the directions of anisotropic axes to be known beforehand. To develop this new method, a simple and accurate solution of elastic deformation of the hole of an anisotropic hollow cylinder has been newly established. Further, an effective way of reducing the number of independent parameters for orthotropic anisotropy has been established through theories and measured data. Then it is shown that the anisotropy can be back-analysed stably using the deformation of the hollow cylinder.

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The vacuum pre-loading is advantageous over the conventional pre-loading method since the effective stress increase in the ground may be achieved by having comparatively small-scale equipment and by avoiding any danger of ground failure during embankment. Currently, this method suffers from a drawback that neither the strength nor the deformation of subsoil during and after the pre-loading is systematically manifested. In this study, negative pore water pressure loaded to specimen, which assumed the stress state of the original ground in triaxial testing system. From the test results, the authors proposed to recognize that the strength increase after vaccum preloading is due to the “preconsolidation effect” and pointed out the importance of assessing effective stress change after the discharge of vacuum.

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In-situ rock shear tests and laboratory shear tests are common for evaluating shear strengths of rock masses and rock cores. However, these methods are rather time consuming and costly, so that they are not appropriate for preliminary stage of geotechnical investigation. In this study, a novel technique of instrumented drilling under cyclically controlled thrust (ID-CCT) is developed as a simple and inexpensive sounding method for evaluation of strength characteristics of rock ground. A series of prototype drilling tests are conducted in two kinds of rocks, siltstone and tuff breccia, to investigate the influence of drilling conditions on the results of ID-CCT sounding. The tests demonstrate that the obtained results are insensitive to various drilling conditions except the type of drilling bit.

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From a series of in-soil creep test, it has been found that the deformation and strain increment of geogrid due to creep is concentrated in the vicinity of pull-out opening. Based on the comparison between calculated in-soil creep deformation behaviors by using the method proposed in this paper and those observed by in-soil creep test, it has been pointed out that it is important to construct a reinforced soil structure so that sufficient frictional resistance develops between soil and geogrid. The importance of the establishment of design method considering the overall deformation of the reinforced soil structure due to the in-soil creep deformation of geogrid has also been pointed out.

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Several specimens should be prepared when strength characteristics of rock is evaluated by conventional single-step loading triaxial compression tests. On the contrary, multiple-step loading triaxial compression test, hereafter denoted as ML-TCT, is advantageous as shear strengths for different confining pressures can be obtained on a single specimen. ML-TCT, however, is not established as a standard test method, because of possible under-estimation of shear strengths due to accumulated damage by repeated axial compression steps. In this study, Multiple-step loading damage model is proposed to simulate ML-TCT properly, and appropriate number and procedure of axial compression steps for ML-TCT are investigated.

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The incremental nonlinearity has been studied experimentally and theoretically for the exact modeling of mechanical behavior of geomaterials. However, the micro-mechanical origin of the incremental nonlinearity has not yet been clarified. We discuss the micromechanism with the aid of discrete element simulations. The results obtained by a series of stress probe tests, which are conducted under the true tri-axial stress states in terms of the 3D-GEM, suggest that the behavior of granular materials have to be described by the incremental nonlinearity. The characteristic deformation modes and fabric parameters calculated for each stress probe give important information to clarify the micromechanism of incremental nonlinearity.

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The sand compaction pile method is the most frequently used methods as a countermeasure against liquefaction of sandy deposits. The authors have already proposed a method to predict the SPT N-value after compaction. It is, however, found that the method does not appropriately consider the effect of fines content of soil deposits on the compaction efficiency. This paper describes the correction of the proposed method for the fines content effect. The correction is done on the basis of the relationship between the fines content and the drainage characteristics of soils, and the drainage effect on the dilatancy behaviour of soils during cyclic loading. And it also describes the effect of the driving rate of the sand pile on the compaction efficiency by considering the effect of the driving rate on the drainage of the soil deposits.

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The authors tried to evaluate the stability of the rock slope at Honzon-iwa where rock fall and rock block failure had occured frequently considering mechanism of the rock block failure. The authors tried to detect vulnerable locations by visual inspection of rock face. The locations pointed out were in accordance with the stability evaluation of the whole rock slope. Consequently, it was concluded that there were no drastically effective measures except the relocation of the road considering the high degree of risk to the present route. To maintain the present route until the completion of relocated route, temporary measures consisting of rock stabilization, rock fall protection and monitoring system were taken.

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When a tunnel is submerged, the air is stayed in it. Here, the rock mass surfaces are exposed in the tunnel. The condition of water sealing for the staying compressed air is that, the pressure of the compressed air is smaller than the pressure of void water pressure in rock masses. By the results of measurements, it is ensured that the compressed air stays for ten months in the tunnel. Moreover, the change in terms of the time of void water pressure in rock masses have been cleared. Then the outline of the results for the field measurements will be described.

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A laser displacement measurement and AE monitoring were employed to monitor an unstable rock mass left after rock block failure, to secure repair works under it. Accumulated displacements around 50mm were measured for 20 days. However, since neither rapid increase of the displacements nor active AE occurrence was observed, it was considered that the rock mass was stable and a failure would not occur soon. The fact that the rock mass did not failed down in spite of such a large displacement of 50mm suggests that various kinds of displacement measuring techniques having not so high accuracy are applicable if continuous measurements are conduced. The results also indicate that AE data are very helpful to judge risk of rock mass failure.

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Recently, we have a very difficulty to repair the leakage of the small old earth dams because of the shortage of suitable impervious soil. This paper represents a improvement method of impervious property of embankment soil in such a dam. This method is the mechanical stabilization of embankment soil obtained from the existing old earth dam need to repair the leakage by adding mud soil in the reservoir.
A series of laboratory tests was performed to investigate the effect of mud soil content on the permeability of a embankment soil stabilized mechanically by adding mud soil. The test results show that the permeability of a mechanical stabilized embankment soil is reduced to less than 1×10^-6cm/sec by the addition of about 10% of mud soil.

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The water absorption by the roots of plants was focused as the main reason of the increase of suction in the ground. Field measurements were carried out to study the effect of the roots of plants on a long-term change of the suction in the ground by using tensiometers. It was made clear from the measurement that the water absorption by the roots of plants plays an important role in the recovery of the suction after rainfall and obtained some knowledge on the difference in the suction by the season in a year, the time in a day and species of plants.

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The measurement of elastic wave velocity is effective as the technique which grasps elastic characteristics of rock, and recently the evaluation by S wave is mainly carried out. In this paper, it is tried to develop the simultaneously measured system for P, S wave velocities and electric resistivity of a rock sample and to manufacture the laboratory equipment. In this system, P and S wave are analytically found out from the recorded waves. And on the same time, the electric resistivity of this rock specimen is measured by geo science method. Furthermore, P, S wave velocities and electric resistivity obtained from this system are compared with these quantities given by the usual measurement methods. As the results, it is confirmed that this measurement system is useful for the various rock specimens.

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To examine the effect of the propagating directions of shear waves and the pluviation directions of specimen on the shear wave velocity of sand, the shear wave velocity in three different directions was measured by the bender element method under anisotropic stress conditions. The triaxial specimens were cut from the frozen sand blocks in the directions of vertical and horizontal. Test results showed that; 1) the shear wave velocity more depends on the normal stress than the parallel stress relative to the bedding plane, 2) the velocities of two kinds of shear waves, whose propagating or vibrating directions are vertical and horizontal directions, are almost same under anisotropic stress conditions irrespective of the fabric anisotropy.

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