In any projects involving the use or treatment of slurry clay, the shear strength, that is, the yield shear stress is an important parameter. Currently it is obtained indirectly through extrapolations of data from either viscometer or "vane-type" shear tests which have a number of shortcomings. A direct method which relies on the vertical penetration of a thin plate or a thin hollow cylinder under an incremental load is proposed in this paper. The yield shear stress mobilised at equilibrium is then obtained and compared with that from a series of viscometer tests. The very good agreement confirms the validity of the method which is easier to use and able to give the parameter directly. The rheology of the slurry clay is then studied and is found to be governed by a Bingham model at low strain rate and a power law model at higher strain rate. For different clays, when the yield shear stress is plotted against (water content/liquid limit), a unique relationship is obtained. Also there is a pronounced change at a limit of 2.0, below which the slurry becomes a paste. In this paper, this limit is termed the slurry limit.

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A series of field and laboratory tests was conducted on an Ariake clay found in Kyushu Island of Japan. Undrained strength values obtained from K_Oconsolidated triaxial compression and extension, direct shear, field vane, unconfined compression and cone penetrometer tests are first presented together with the relationships among these strengths. Consolidation yielding stress determined by two types of oedometer tests are also presented and discussed, and a new procedure of determining consolidation yielding stress of this clay is proposed. Undrained strength for stability analysis determined with considerations both on strength anisotropy and strain rate effect is presented and related to various undrianed strengths and consolidation yielding stress. Finally, change of compressibility through loading in the normally consolidated state is investigated. It is revealed that the change of compression index in the normally consolidated state reaches several times and this change should be taken into account in evaluating settlement behaviour.

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Active and passive earth pressures acting on retaining walls are known to be a complicated function of many factors, for instance, the cohesion and friction angle of backfill material, wall friction, and geometries of wall and backfill. Conventional theories based on stability analysis, e.g., Coulomb and Rankine methods which are now quite widely used, cannot necessarily take all these factors into consideration. Firstly this paper develops a numerical procedure for calculating active and passive earth pressures against rigid retaining walls, which enables to take account all these factors affecting active and passive pressures, and which presents full information about the earth pressures. Secondly, by comparing the procedure with Coulomb and Rankine methods, this paper aims to clarify the mechanical and practical meanings of these classical methods. Based on the lower-bound theorem in the theory of plasticity, the procedure searches the minimum and maximum values respectively of active and passive thrusts within the limitations of satisfying the equilibrium equations and non-failure condition. To represent these conditions, the earth pressure and the stress field within backfill are discretized in a similar manner as in the finite element method. On the problem formulation, two methods are considered depending on whether a potential slip surface is assumed or not. When assuming a slip surface, arises a serious difficulty that the criterion for locating the critical slip surface is contrary to the criterion for determining the stress field. When assuming no slip surface, it is shown that the proposed procedure provides the reasonable solutions of active and passive pressures and that the boundary condition of wall and backfill movements has an essential meaning in the analysis. The procedure is applied to a number of case studies, where comparisons are made thoroughly with classical theories. Through the development of the procedure, many important aspects in the earth pressure problems are clarified.

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Changes in shear wave velocities, V_S, which occurred during triaxial compression tests were measured on undisturbed samples obtained from a diluvial gravel deposit by an in-situ freezing method. Measurements on the reconstituted gravel samples were also conducted to compare the characteristics of shear wave velocity. The results of these measurements indicated that V_S increases at the initial stage of the triaxial compression tests, and decreases gradually until the failure of specimen and that the reduction in V_S was more noticeable for the undisturbed samples than for the reconstituted samples. The difference in the V_S reduction behaviour for the undisturbed samples and the reconstituted samples became remarkable after the expansive volumetric change occurred during triaxial compression tests. The results also revealed a unique relationship between V_S when evaluating the effect of stress ratio and confining pressure for both undisturbed and reconstituted samples at failure. Index of shear wave velocity is introduced to express uniquely the change of V_S in both undisturbed samples and reconstituted samples during triaxial compression tests.

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Design of foundations subjected to dynamic load can be carried out either by elastic half-space theory or by mass-spring-dashpot analogy. Another simplified method, called analog method has also been proposed. Using this method resonance frequency and resonant amplitude which are the major criteria in design of machine foundations, can be expressed in terms of modified mass ratio knowing appropriate damping factor. In this paper analog solutions in the form of equations (non-dimensional frequency factor vs. modified mass ratio, non-dimensional magnification factor vs. modified mass ratio) are presented for all modes of vibration, viz., vertical, horizontal, rocking and torsional. Finally results obtained by this method are compared with elastic half-space theory which shows good agreement between the two.

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The utilization of industrial wastes as cement replacement material is one of the most desirable methods to solve environmental problems posed by the production of these wastes. Concerning beneficial aspects, the potential uses create new construction materials. There are only a few studies that have been reported on the effective utilization of slag obtained from stainless-steel factory. The objective of this study is, therefore, to illustrate the potential use of a stainless-steel slag as a blended cement material, and to elucidate the contribution of blended slag cement to the development of strength for seabed dredged sludge (hedoro). The present study investigates hardening effects through the two important strength parameters, unconfined compressive strength (q_u strength)and California bearing ratio(CBR). Evaluation on reaction rate of tricalcium silicate (C₃S) using X-ray diffraction analysis is proposed, and representative data are obtained. Based on the experimental results, the q_u strength of the hedoro stabilized with slag cement is higher than that of cement-stabilized hedoro in all respects. It is concluded that the slag powders added significantly accelerate the initial reaction rate of C₃S, resulting in an increase in short-term and long-term strength. The development of strength in relation to the hydration mechanism of C₃S is then discussed.

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In the suburb of Dushanbe, Tajikistan Republic of USSR, an earthquake of magnitude 5.5 took place on January 23, 1989. In this event, extensive liquefaction developed in the loess deposit of aeolian origin in the gently sloping hilly terrain and led to a series of catastrophic landslides accompanied by a large-scale mud flow. In contrast to the hitherto known cases of liquefaction which have usually occurred in water-sedimented sand deposits, the liquefaction in Tajik was unique and novel in that it occurred unexpectedly in a windlaid deposit of silt in a semi-arid region. The reasons for such a liquefaction are thought to be the collapsible nature of highly porous loessal silt which had been wetted by irregation water over the past years. The complete collapse of the loess structure due to the additional action of the seismic shaking appears to have led to the catastrophic landslide. In addition, the silt-sized soil constituting the loess was of low plasticity and hence could easily slump and flow through a distance as long as 2.0km.

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The mechanism of the wave-induced liquefaction and densification in permeable seabed is examined with particular reference to the excess pore pressure. A concept of the 'oscillatory' excess pore pressure has been introduced and verified by model experiments using a newly developed apparatus. The following main conclusions are drawn from the study; 1)the oscillatory excess pore pressure is excited in the seabed where the wave-associated bottom pressure is propagated into the seabed with some damping and phase lag, 2) the magnitude of the change in the effective stress is identical with the oscillatory excess pore pressure, 3)the liquefaction and the densification occur alternately in the seabed, even in one period of the wave loading, and 4)the wave-induced liquefaction is quite different from the earthquake-induced liquefaction in the mechanism of the generation of excess pore pressures.

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Slurry disposal is a problem faced by many engineers dealing with mine tailings. In this paper, a study on the behaviour of a typical slurry is reported. When the slurry is very dilute, it undergoes particulate settling which is very slow. For treatment, it is desirable that the slurry undergoes hindered settling where the soil particles settle en-masse. When the soil partices settle and the water content of the slurry is reduced, it begins to gain in strength dramatically. This gain in strength may be small from a conventional soil mechanics view point but it can be used to treat the slurry. One way is to lay a thin layer of sand as a horizontal drainage layer on the slurry once it gains sufficient strength to arrest the settling of sand particles. Once this is feasible, a reclamation scheme whereby alternate layers of sediment and sand are constructed to reduce the drainage path of the fill can be considered.

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With the development of large-scale offshore reclamation, the long-term deformation of the diluvial clay deposits situated deep in the foundation ground has become an issue, along with the deformation and stability of the alluvial clay deposits sedimented near the seabed. Detailed studies are needed to estimate the above time-dependent behaviors of clay foundation in order to control the harmful effects of ground movements on superstructures and their foundations. Coupled stress-flow analysis, in terms of the elasto-viscoplastic finite element method, is performed to evaluate the deformation and stability of a marine foundation due to the construction of reclaimed land. The calculated performance ascertains a stable process of deformation and the stress state during revetment construction and reclamation. Furthermore, the measured settlement, lateral displacement and excess pore water pressure profiles agree well with the calculated performance.

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The stress-strain behaviour of clay around a pressuremeter was investigated using the program DACSAR, a finite element program based on an elasto-plastic constitutive model. To check the program, a series of miniature pressuremeter tests were conducted in a sample of soil in a triaxial chamber, and the results were compared to those predicted using the program. The input parameters for the modelling were obtained from standard laboratory tests. This exercise showed that the clay behaviour could be reasonably well simulated using of the DACSAR program. In addition, it was demonstrated that the miniature pressuremeter test was not an accurate model of an in situ test, because of the effect of the finite dimensions of the sample in the triaxial cell on the pressure-expansion behaviour. Partial drainage was also shown to have an effect on the response in the model tests, and this effect was also reproducible with the DACSAR program. The DACSAR program was also used to investigate in situ pressuremeter tests in clay. The analysis showed that the stress-strain behaviour of the soil around the pressuremeter may be strongly influenced by partial drainage, with this effect being dependant on the permeability of the soil and the rate of testing. Consequently, when the so-called "Sub-Tangent" method was used to deduce the stress-strain curve from the numerical "tests", the derived "undrained" shear strength was higher than the true value, because the assumptions of undrained behaviour and plane-strain deformation, on which the method is based, are violated to some extent.

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The oscillatory pore pressure excited in porous seabed by ocean waves is theoretically and experimentally examined in the context of the wave-induced liquefaction. A govering equation on the oscillatory pore pressure is presented and verified with the model tests. The comparisons of the finite difference solutions with the measurement of the oscillatory pore pressure have shown a good agreement. The governing equation is also adopted to estimate the liquefaction potential of the model seabed and its applicability is confirmed. It is shown that the wave-induced liquefaction is a kind of quick sand caused by the upward seepage force induced repeatedly in the seabed by ocean waves.

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A series of shaking table tests of earthen embankment founded on saturated sand ground was perfomed. Six reduced scale models were subjected to different input accelerations. The results of this experimental study show the followings : (1) when the model is subjected to shaking, the ground beneath the embankment does not liquefy, whereas the ground in the free ground easily liquefies, (2) the soil that has liquefied exhibits sharp response acceleration, (3) embankment slumps and cracks as a result of softening of the underlying ground associated with porewater pressure generation. The extent of such damage is more extensive when subjected to an earthquake input motion of vibrational type with longer duration and lower frequency. Further, the experimental response of the models and especially the spiky accelerations are explained by using an inverse technique to reconstruct the local response of soil from measured data. This inverse technique shows that the spiky accelerations were caused by cyclic mobility effect and that the liquefaction largely depends on the spatial variation in stress condition.

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This note proposes a numerical procedure in which the material parameters affecting soil dynamics are back-calculated from the acceleration response monitored in the field. By assuming the values of soil parameters, the acceleration response of the dynamical system is calculated by a finite element analysis in time domain. Because the direct comparison in time domain between the calculated and monitored accelerations has less reasonable meaning, the Fourier coefficients both of the accelerations are calculated. And the least squares method is applied to the Fourier coefficients corresponding to the calculated and observed quantities respectively. The formulated problem is successfully solved by mathematical programming technique. As the first phase of the research, the back-analyzed soil parameters are Young's modulus and damping coefficients by assuming the linear elastic behavior and the viscous damping of subsoil. The proposed procedure is applied to hypothetical case studies and its validity is verified. Subsequently the trial application of the procedure to actual case study is discussed which is concerned with the parameter estimation in soil deposit during an earthquake.

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