This paper describes (1) the determining procedure of the undrained strength of Iraqi alluvial clays for practical use and (2) the results of stability analysis for sliding of the jetty at Fao and Khor Al-Zubair, located on the mouth of the Shatt Al-Arab and on her old river channel respectively.From the considerations on the undrained strength for practical use and on the stability analysis (including the field observation), following conclusions were obtained : -(1) The undrained strength of Iraqi alluvial clays distributed along the Shatt Al-Arab should be fundamentally determined from the in-situ vane tests.(2) From the comparison of the results of stability analysis and of the field observation, it was suggested that factor of safety for sliding obtained using the undrained compression and extension strength, S_u(c) and S_u(e) may better represent the actual one.

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The purpose of this study is to investigate the propagation characteristics of the traffic-induced vibrations and to make a prediction method of the attenuation with distance of the traffic-induced vibrations. To do this field tests were performed by using test trucks and ground vibrations were measured on the ground surface and in the ground at depths of 2 and 4m. Moreover the investigation of the real traffic-induced vibrations all over Japan was carried out and ground vibrations were measured as far as 20m from the center of the outside lane.Conclusions obtained from the investigations are following : i) The Rayleigh wave is dominant in the traffic-induced vibrations. ii) The vibration due to large truck (the mass is about 20Mg) has almost same frequency as small truck (the mass is about 10Mg). Frequency of the traffic-induced vibrations is mainly determined by ground soil conditions. iii) The higher the frequency of the ground vibration is, the larger the attenuation with distance is. One of reasons on this is that soils have rate-independent damping characteristics. iv) The larger the acceleration at reference point (at a distance of 5m from the center of the outside lane) is, the larger the attenuation with distance is. One of reasons is that the propagation velocity and the damping ratio of soils depend on shear strain even in a very small strain region. v) In the condition that the acceleration at reference point is same, soft ground has smaller attenuation with distance than hard ground. vi) Quantitatively vibration level recuces 1-7 dB per double distance.

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To evaluate the effects of various static stress conditions and stress histories on shear modulus and damping of sand under cyclic loadings, a comprehensive series of cyclic torsional shear tests on hollow cylindrical specimens of a clean sand was performed. All the tests were performed and the constant value of mean principal stress =1.0 kgf/cm² (about 100 kN/m²) under fully drained condition. From the test results, the followings were found. For a wide range of shear strain amplitude (γ=5×10^-5∼5×10^-3), the effect of stress ratio on shear modulus is minor in the triaxial compression case but considerable in the triaxial extension case. Initial shear stress decreases shear modulus especially for the triaxial compression case. Although shear modulus is affected by various static stress conditions, its strain-dependency is insensitive to those static stress conditions. The effects of stress ratio and initial shear stress on damping ratio are less important than shear strain amplitude γ and mean principal stress p. It was found that the effects of overconsolidation history and previous larger cyclic shear stress history on G and η are also less important than γ and p.

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Undrained triaxial compression and extension stress-strain behaviour of a saturated remolded clay consolidated under K₀ and isotropic stress conditions was investigated. Test results indicate that octahedral stress ratio-strain relationship and effective stress path in octahedral stress space were affected by the stress system during shear as well as the stress condition during consolidation. Moreover, it was also found that not only undrained shear strength but also effective angle of shearing resistance were influenced by the two factors mentioned above. Octahedral stress ratio versus dilatancy curve was approximately represented by a set of two straight lines.Based on the test results, the authors proposed a new method of predicting undrained stress-strain behaviour of K₀ consolidated clay by using the data obtained from isotropically consolidated undrained tests.

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Cyclic shear stresses, τ, with constant amplitudes are applied to a dry sand up to 1, 800 cycles under constant over-burden pressures, p, using the simple shear apparatus in order to clarify the factors affecting the deformation behaviours under cyclic loading. The following results are obtained. The rotation of shearing direction by 90 degrees in the middle of a test does not affect the volume change.The deformation characteristics under cyclic loading are controlled mainly by the stress ratio, τ/p, and are divided into two phases by the stress ratio of critical disturbance (τ/p)_c. Namely, an amount of volume change accumulated during 1, 800 cycles of shearing increases abruptly when τ/p≥(τ/p)_c. The influence of an initial structure of grains on the deformation behaviours disappears by repeated cyclic loadings when τ/p≥(τ/p)_c; however, this structure remains intact partially when τ/p<(τ/p)_c. Moreover, the deformation by the stress application after stress reversal is not affected by the stress application before the reversal when tested in the stress range of τ/p≤(τ/p)_c, but affected in range of τ/p>(τ/p)_c. The stress ratio of critical disturbance (τ/p)_c increases as the void ratio of a sample decreases and it can be obtained by static shear tests. A fundamental and unified explanation of these experimental results is given by the two-dimensional stress-dilatancy model which is built on the basis of the concept of shifting the position of the sliding contact point in a limiting equilibrium state. As a result, the stress ratio of critical disturbance can be defined as the stress ratio by which all the points of contact are slid in one cycle, and the following relation can be satisfied : max (τ/p)_c=(τ/p)_dv=0=tan θ_μ.

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A true triaxial shear test box equipped with six rubber pressure bags was constructed to test cubical specimens of sand with a dimension of 100 mm×100 mm×100 mm. A series of drained tests was carried out on loose sand specimens prepared by depositing the sand under water. The tests employed different radial stress paths in which the major, intermediate and minor principal stresses were oriented independent of the direction of the specimen sedimentation. The test results indicated that when the shear stress was small the deformation of the speciment thus prepared was highly anisotropic because of the inherent anisotropy of the specimen, but when the shear stress became large enough to produce failure the effects of inherent anisotropy disappeared. A number of tests were also carried out on specimens rotated by 90° about the horizontal axis after the specimens had been prepared by deposition.

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