The main object of this study is to clarify the strength and deformation characteristics of mudstone deposited during the Tertiary Period, which is widely distributed in Japan, for the wide range of effective confining pressure σ′_m (=294kPa-5880kPa) during cyclic loading. It is found that degradation of shear strength according to increase of the number of cycles is relatively small in comparison with that of soft soils. Shear strength mobilized at irregular cyclic loading tests using actual earthquake acceleration records is about 110%-120% of that obtained by monotonous loading tests, and the relation between shear modulus G and σ′_m at small strain level is expressed by two straight lines with breaking points, which is given σ′_m equivalent to consolidation yield stress, in the log scale paper.

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To clarify mechanical properties in particular strain rate dependency and cyclic effect on strength and deformation of mudstone with weak plane, triaxial and cyclic triaxial compression tests are performed on specimens which has discontinuous plane with variable angle θ to the maximum principal stress plane. We mainly describe dependency of strength and deformation on the angle, and deformation characteristics during cyclic loading, and strain rate dependency of strength and Yong's modulus. Particularly, it is found that maximum deviator stress (σ₁-σ₃)_f at θ=60° nearly equals the residual strength, and rate dependency of strength clearly can be seen for the wide of strain rates, and (σ₁-σ₃)_f at θ=60° can be given by failure criterion for residual strength of intact specimen based on effective stress.

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For a rational estimation of the design impulsive load to rock fall protection structures due to rock falls, a test set-up with a tower of 24.8m height for the rock fall experiments has been constructed.
Using this test set-up, the impulsive accelerations of weights simulating falling rocks and the impulsive earth pressure through a sand layer which acts to the rock fall protection structures are experimentally measured. The effects of the weights, shapes and falling heights of the falling rocks to the impulsive acceleration and the earth pressure are investigated.

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This paper discusses the results of experiments on the settlements of poor cohesive soil ground caused by tunnel driving with a slurry shield. Driving tests were conducted with a slurry shield model having the diameter of 600mm in the laboratory and an actual performance of slurry shielding was compared with the model test. The model tests show that there exists an optimum slurry pressure dependent on the overburden pressure and ground materials, and the ratio of the amount of soil to be excavated to that estimated from the shield diameter is nearly 96 to 97% for the optimum pressure. The field tests show that the optimum pressure is nearly equal to the pore pressure, and the optimum driving speed is such that soil at the face is kept in the region of somewhat passive condition.

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This paper discusses the ground behavior during excavation of thin overburden tunnel in unconsolidated ground with the results of field measurements and numerical analysis.
Horinouchi and Tokko tunnel on the Narita Shinkansen Line provide the data for this paper. These tunnels were constructed in the diluvial sedimentary soil layer of very poor quality at the depth of 4-11m from the ground surface.
In this study, the mechanism of ground settlement, the condition of ground arch formation and the estimation of the amount of settlement of surface at each stage of excavation were obtained with looking upon the sorrounding ground as macroscopic elastic body.
This paper will be the usefull guide for designing and monitoring the similar tunnels.

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In this research, liquefaction tests by impact were performed for both improved ground with a single gravel pile and unimproved ground. We found that surface settlement of improved ground was larger than that of unimproved ground. And we obtained some knowledge of distribution pattern of pore water pressure in the improved ground. On the basis of these test results and some assumptions, we proposed a simplified designing formula for gravel piles against liquefaction during earthquakes. Shaking table tests were also performed in this research to represent that the simplified designing formula was proper from engineering point of view.

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In the small diameter pipe jacking method, a demand for a tunnelling machine, with which long and curved tunnels can be constructed, has grown in recent years. It is necessary for constructing curved tunnels to control the direction of tunnelling machine. This paper describes the design of tunnelling machine for controlling its direction, whose direction control is achieved by both directional control mechanism and position measuring system. The tunnelling machine designed based on this method has been used for constructing 50 meters long tunnels in silty loam deposits whose curvature radiuses were smaller than 200 meters. Experimental results show that this design method can realize long and curved tunnel in small diameter.

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In case of construction of an additional structure outside of the tunnel, enlargement from the inside would be more economical and time-saving comparing with conventional cut and cover method.
This paper presents how to enlarge the segmented lining tunnel under soft ground of water-bearing soil by application of slurry shield tunneling technique, and how to design enlarged structure of the tunnel.
Furthermore the design problems are clarified through prototype experiment to build composite structure with primary segmental lining which is already affected by stress prior to placing secondary lining.

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In order to detect the microscopic behavior of sand particles, acoustic emission emitted from sand under various shear stress levels was measured. From these experiments the following conclusions were obtained. (1) Acoustic emission and stress-strain relationships under two types of repetitional shearing tests were compared. One was the ordinary repetitional shear test. The other was the repetitional shear test on the sand which had been subjected to the repetitional shear along the direction perpendicular to the shear direction. Each compared characteristic was found to be different. (2) Kaiser effect of sand was realized according as the sand became elastic. (3) From the pattern of relationships between applied stress and number of acoustic emission three states of sand-elastic, elastoplastic and failure states-were classfied.

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The structure is composed of a superstructure and foundation. The superstructure and foundation are designed separately in the present design method, but it is an ideal that the optimum design of a structure is carried out as one system. The present paper describes the procedure of optimization for system reliability of spoil-supported structure. Each optimum design alternative of a superstructure and foundation is decided by minimizing the expected total cost as a whole. The plate girder bridge constructed on the poor ground is examined as a case study. The optimum safety factors of the main girders and the foundation are decided from the view point of system reliability.

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The present paper makes the important part of a series of study on the earthquake-proof design method and the examination method for aseismicity of slopes and earth structures. The failure case and the adjoining non-failure case of embankments and slopes under the actual earthquakes are inversely analized. As a result, the distributions of the seismic coefficient κ which can significantly distinguish the failure and the non-failure cases in the statistical meaning are obtained. In addition, the attenuation equations are investigated by the regression analyses of the measured maximum ground accleration α and the (κ-α) relationships for design and examination are proposed. The methodology to judge the degree of safety under earthquake is also shown.

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We observed in the previous experiments that the pore pressure produced by the repeated shear stress is two or four times as much as the one by the static shear stress and therefore the repeated shear strength decreases in proportion to the increase of the pore pressure. So, in this experiments, the volume change which attained to an ultimate value depending on the shear strain amplitude and the pore pressure generated during cyclic shear were measured and the relations of them were investigated. As a conclusion, the volume change converted from the pore pressure increase using the coefficients of volume expansibility was a half of the one obtained in the cyclic shear tests with drainage.

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The studies of decomposed granite soils in undisturbed state have been done by means of new sampling and testing technique. But because of the poor situation with regard to relevant literature, the classification system for engineering purposes have not been established, so that these results of studies on the sample taken from various localities do not have compatibility with each other.
The paper proposes a classification system for engineering practice in the decomposed granite soil on the basis of physical and mechanical properties.

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A sand is a complicated material that is associated with dilatancy by loading and is also largely influenced by stress histories. In order to represent the characteristics of sand, subsequent anisotropy, which is induced by dilatancy accompanying plastic deformation, is evaluated on the basis of the results obtained from simple laboratory tests under axisymmetric stress conditions. Furthermore, an elasto-plastic stress-strain relation for sand is derived from considering a sand as a strain hardening material not only for shear but also for compression and adopting stress-dilatancy relation. From comparisons of the calculated results with the strains measured in the stress path tests with complex stress histories, it is shown that the proposed equation may be useful in prediction of the stress-strain behaviour of sands.

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In order to investigate influence of fabric of clay soil on shearing behaviour, three kinds of samples were prepared which have different fabrics, that is, naturally deposited undisturbed sample, artificially consolidated samples which were remoulded under higher water content and under several water contents lower than the liquid limit. The consolidated undrained triaxial compression tests were carried out for these samples under normally consolidated, over consolidated and cyclically sheared states. The influence of fabrics on shearing behaviour can be found in Fig. 12 and Fig. 13 which show the relationship between the coefficient of pore water pressure A_f and the parameter b which is determined on water content-logarism of consolidation pressure diagram.

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An elastic-plastic constitutive model is presented in this paper which is capable of describing the cyclic behavior of sands reasonably accurately. A non-associated flow rule is used by modifying the model available to monotonic loadings. Undrained cyclic triaxial tests are simulated and the results are compared with the experimental data. The numerical formulation and solution techniques are presented to analyze the dynamic behavior of sand deposits subjected to earthquake shocks. The characteristics related to liquefaction are investigated about the effective stress path, liquefaction zone and pore pressure. It was shown that the permeability coefficient can significantly influence the response of the ground during earthquakes.

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Long life and reliability in pumping abrasive slurry are more important than initial cost and efficiency. Here, several wear tests for impeller, reducer and frontliner of unshrouded centrifugal pump were executed at 2 sites of shield tunneling work. The influences of soil and metal including some surface coatings properties on the wear characteristics of pump parts were investigated. As the results, the effects of surface coatings treated on a reducer are displayed remarkably at initial stage of wear. To prevent the eccentric wear at a bottom of reducer or frontliner, it is necessary to increase the flow velocity at the inlet of pump not to occur a state of bed-load slurry movement, or to rotate their setting positions periodically.

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Strength properties of sandstone prepared in cylindrical specimens with different moisture contents were studied using triaxial compression test under confining pressure in the range of 0 to 80MPa. It is shown that the relations between strength and confining pressure are generally non-linear, and the non-linearity depends on the moisture content of specimen. In order to express these strength properties of sandstone, Lade's failure criterion for soil with curved failure surfaces was extended for including the tensile strength in the criterion and was applied to the test results. As the results, it may be concluded that this failure criterion is available for rock as well as for soil when the value of material parameter related to tensile strength is determined from the uniaxial tensile or compressive strength.

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