During the 1995 Hyogo-ken Nanbu Earthquake, significant surface breaks occurred along a pre-existing active fault, the Nojima Fault on the northwestern coast of Awaji Island, Japan. In order to elucidate the characteristic structures of surface deformations as well as underground fault patterns, detailed sketching and surveying were carried out of the surface rupturing and a series of physical exploration by ground radar method were conducted of the internal faulting.

View full abstract

In a wide area of the near-shore reclaimed land, a very large bulk of mud was ejected immediately after the Hyogo-ken Nanbu Earthquake on 17 January 1995 and the ground subsidence of 30-50cm or more was observed. Such a noticeable settlement is considered to be mainly caused by the liquefaction in a sandy soil layer with about 20m thick which is underlain by the alluvial clay layer. However, there are many unknown factors about the earthquake-induced settlement of alluvial and Pleistocene clay layers. In this paper, the dissipation of the earthquake-induced excess pore water pressure and the post-earthquake settlement-time relations of clay layers are investigated.

View full abstract

The strong ground motions obtained during the 1995 Hyogoken Nanbu Earthquake are discussed from view points of strong-motion peaks and wave propagation characteristics. The consideration of strong-motion peaks shows that the event is usual one relevant to its earthquake magnitude. On the other hand, in order to interpret wave characteristics for the motions, the array records observed at Port Island are used. It is concluded from various analyses such as non-stationary spectra, cross correlations, etc. that the main part of the strong motions is composed of body waves and surface waves. Especially, the existence of surface waves, which are considered to be generated by the edge effects of the basin, suggests that they might have strongly affected the earthquake damage.

View full abstract

The Great Hanshin earthquake occurred on January 17th, 1995. Structures of 27 fishing ports were damaged. This paper presents the results of investigation of damages of the ports and liquefaction analysis of Kariya fishing port and Tarumi sea pasture as a representative. Damage characteristics were examined as the damage pattern of structure's type, direction dependence of damage compared with the main earthquake motion. Comparative study of liquefaction between one dimendional and two dimendional analysis was carried out.

View full abstract

An expand displacement method is presented to analyze the response of pile foundations. The method's suitability is then verified with an in-situ lateral loading test First, it is assumed that the pile behaves non-linear and yields with a plastic hinge area Ls, the length being equal to the diameter at the pile head. The proposed equation treats the spring constant, K₁*-K₄*, as a function of Ls. Then, a equivalent linear model is constructed to describe the non-linear response of pile foundations. The non-linear coefficient, y, is suggested for each ground type. Analysis result of the expanded displacement method has shown that the observed relation of H-δ of a in-situ loading test of a pile foundation can be simulated approximately, and it has a similar accuracy to the result of the pile-rigid frame method in the Specifications.

View full abstract

In the 1995 Hyogo-ken Nambu Earthquake, the soil liquefaction caused serious damage to the levees at the Yodo-river in Osaka city. The authors developed two kinds of analysis codes named EFFCTD and BOWL. These codes are based on the effective stress method. Using these programs, we carried out the simulation of the damage to the levees at the Yodo-river based on the following two steps: the dynamic analysis during the shaking and the static self-weight analysis evaluating the residual displacements (AD-MINGT and BOWL-DEFORM). The results of the analysis can express the damage of the dike qualitatively, but the liquefaction induced settlements and lateral displacements are underestimated.

View full abstract

The empirical law is introduced considering fuzziness involved in the characteristics of soils. A model proposed in this paper is based on the viscoplastic model. The proposed model has the learning ability via the descent method and it enables the model to get preferable degree of accuracy and to be adaptable to some kinds of characteristics of compound soils. Three items are coordinated as a first step. Physical meanings of dynamics of the viscoplastic model, introduction of the empirical law with fuzzy inference rules, and the effective learning ability.

View full abstract

A collapse of an underground quarry in Ohya district, located 7km west of the center of Utsunomiya city, caused a large scale subsidence about 3, 300m² wide. Unfortunately, subsequent large scale subsidence has occurred in this district. In order to explain the reason why such large scale subsidence occurred, the authors investigated strength deterioration and creep characteristics, and discussed the mechanism of the collapse. A collapse control with the cross section area and spacing of pillars was also discussed in this paper. According to a correlation between the earth tidal force and the occurrence of subsidence and rock-fall, earth tidal action may trigger collapses of underground quarries under critical states.

View full abstract

Many landslides have happened at sepentinite belts in Japan. The mineralogical and mechanical characteristics of landslides at serpentinite belts were investigated, Clay minerals were analyzed by X-ray diffraction and the angle of shear resistance φ′ was obtained by the triaxial test. The angle of landslides at serpentinite belt was relatively gentle, about 10-20. The φ′ of sepentinite clay, chrysotile and antigorite, was about 30. But the φ′ of soils of the slip surface was about 20. It was cleared that the soil of slip surface involved talc, chlorite and montmorillonite which had a small φ′.

View full abstract

This paper describes the performance of a proposed two-dimentional groundwater model with moving boundaries by employing the zero-extention theory. Charged fronts under unsteady conditions are recognized as moving boundaries. There are three principal parts to the proposed method. The first and second parts consist of directly and inversely analyzing the presented model in a hypothetical basin, respectively. After solving the inverse problem, the third and last part contains a description of the procedure adopted to determine pumping rates with a constraint for pumping demands. Numerical results of direct and inverse problems for the proposed model support the validity of the proposed method in this paper.

View full abstract

This paper presents the centrifuge model tests of heavy tamping to investigate the relation between distance of tamping points and improved depth. The model material was sandy soil. The surface was tamped at several points by a model ram under centrifugal acceleration field of 100g. Then the cone penetration test was carried out at several locations.The improved depth was evaluated by the increase of relative density converted from the increase of cone penetration resistance. The depth of the increase of cone penetration resistance and the increase of relative density were deeper than single point tamping. The optimum distance between tamping points was decided. Finally, a design procedure of heavy tamping on the basis of ram momentum was proposed.

View full abstract

Seismic wave velocities of hard rock mass are very important property because they influence earthquake responses of dams and underground caves. Therefore several types of seismic prospecting have been carried out to obtain wave velocities. In this study, seismic wave velocities are evaluated from data of observed seismic waves and are compared with wave velocities obtained from field tests for hard rock mass with cracks. The differences are found among them and the reasons of the differences are investigated from the point of the density of cracks in the hard rock mass.

View full abstract

The failure of a large discontinuous rock slope causes severe damage not only to economic but to social, thus the stability evaluation of such slopes is a very serious engineering problem. This paper discusses the methods to evaluate the stability using the Base Friction Model Test (BFMT) and the Distinct Element Method (DEM) based on the field measurement data of the large-scale failure caused in a limestone quarry. The results of this study have revealed that both methods are useful ways to perform failure prediction, and also confirmed that the use of both methods at the same time is indispensable when evaluating the stability of discontinuous rock slopes.

View full abstract

Oedometer tests of composite ground were performed to investigate the effects of construction type on consolidation behavior. Specimens of composite ground are made of soft clay replaced by sand in column type or lattice type. In the experiment it is clarified that at low replacement by sand consolidation speed of lattice type is faster than that of column type, and at high replacement this relationship is reversed. Also at high replacement settlement of lattice type is smaller than column type. FEM analyses using constitutive equations for sand and clay predict well the test results. A practical design method of composite ground of lattice type is proposed on the bases of these analyses.

View full abstract

Bottom ash is discharged from every regional incineration plants and is buried at final disposal sites as general waste. It is significant to make use of these sites and bottom ash. Several series of drain triaxial compression tests and undrain triaxial compression tests of bottom ash were conducted in this study. Comparing the results of these experiments with those of past researches about bottom ash, this paper make the mechanical properties of bottom ash obvious. Moreover, several compaction tests, unconfined compression tests, CBR tests and dissolution tests of bottom ash stabilized by cement or lime were performed to investigate the utilization of bottom ash. Consequently, it was dear that the stabilized bottom ash can be utilized into abase course.

View full abstract

With the increasing demands for electrical and electromagnetic surveys in the civil engineering works, the study on electrical properties of rocks becomes essential for the interpretation of such survey results. Since the elastic wave velocities are well accepted for civil engineering, the relation between electrical resistivity and elastic wave velocities is investigated. The resistivity of rocks are measured with various pore water resistivity, and the phenomenon of excess conductance was examined. Those experiments reveal the importance of electric surface conduction, and empirical equations which relate rock resistivity and elastic wave velocity are presented.

View full abstract

We performed a series of pull-out tests of metal strips in in-situ under various conditions, and determined the required relationship between normal stress and shear stress both of which develop usually between strips and filling material. With the results obtained from the above-mentioned test, it has been learned that the Coulomb's failure criterion has been affected between them and, more over, obliquity of the wall facing will be less when friction angle developed between them is more.

View full abstract

When embankment is constructed behind a piled bridge abutment in soft clay deposits, lateral deformation of the clay caused by the fill loading may lead severe damages of the pile foundations. After completion of the backfill, however, ground deformation occurs due to undrained creep and consolidation, and these phenomena may affect the stability of piled structures. In this paper, a series of centrifuge tests were conducted to investigate the long-term behavior. An attempt using FEM with modified Cam-clay model for clay was also made to predict it. From these results, the effects of some influence factors as depth of soft clay and pile tip fixity conditions to the long term behavior were studied.

View full abstract

A method to estimate the bearing capacity of the pile, using the easily obtained data of displacement of a pile head and penetration of the pile or the wave form of particle velocity at the pile head, is presented in this paper. If the wave form of the driving force is estimated, the bearing capacity of the pile should be calculated based on the fact that the penetration of pile is represented by the integration of the particle velocity at the pile toe.
As the results of the examination of the applicability of the method using the actual data, it is shown that pile capacity is determined within the allowable precision.

View full abstract

The authors made a hydraulic rock fracture machine on a trial basis. In this paper, the results of field test, laboratory test and theoretical analysis were described. That is, to obtain an effective fracture, it was found that a combination with empty holes and pressed hole, distance between pressed hole and empty holes, angle of edge were important factors.

View full abstract