The directional strength behavior of a kaolin clay subjected to different stress conditions was evaluated experimentally by use of data from miniature vane shear tests. Clay slurries with flocculated and dispersed intrinsic fabrics were consolidated in large-diameter slurry consolidometers under conditions of no lateral strain to different values of the major principal stress. Upon completion of predetermined stages of consolidation, vertically and horizontally oriented vanes were introduced into the consolidated clay blocks while they were still under their in-situ states of stress, and vane shear strength determinations were made. Similar vane tests were then conducted on unloaded clay blocks to assess the effects of unloading history and back-pressure on the directional strength characteristics. In general, in-situ strength was dependent on fabric and vane orientation, higher strengths being obtained for flocculated clays and horizontal vane orientations. Variations in the unloading history also caused changes in strength, and some of these changes were direction-dependent.

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To evaluate the efficiency of fluid mud disposal in the case of one-dimensional forced dewatering, effects of applied load and clay type on forced dewatering behaviors are examined experimentally. On the basis of the test results, simple semiempirical formulae of forced dewatering are presented. The dewatering velocity is expressed by υp^a, and the time necessary for sufficient dewatering by τp^-βH₀², where p is the applied load and H₀ is the initial thickness of fluid mud. The coefficients υ and τ are markedly influenced by the clay type and less strongly influenced by the initial water content. The lower the activity of the fluid mud, the faster the dewatering proceeds.Analytical examinations of the disposal efficiency suggest that there exists an optimum thickness of fluid mud. A higher disposal efficiency can be attained when the initial thickness is near the optimum value, when the initial water content is lower, and when the applied load is higher. The optimum thickness can be predicted for any fluid mud when the value of coefficient τ, the applied load p, and a property of disposal machine are given.

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The characteristics of the earth pressure acting on a retaining wall are investigated on the basis of the large scale prototype tests in a field. The wall is made of concrete and 10 m in height. The silty sand and the slags are used as the backfill materials. The measured earth pressure at rest and change to the earth pressure in the active and passive states are shown. The influence of displacement of the wall on the magnitude and the distribution of earth pressure in the vertical direction are shown and discussed. The coefficient of earth pressure, the angle of wall friction and the point of application of resultant earth pressure are also examined. Based on the new informations obtained from the tests, the design philosophy of a retaining wall is considered and it is proposed that a general retaining wall should be designed against the earth pressure at rest. Finally the measured earth pressures are compared with the analyzed results by FEM.

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In evaluating liquefaction potential of saturated sandy deposits, it is necessary to estimate undrained cyclic shear strength of soils. On many occassions in actual design procedures, it is very convenient if engineers can evaluate undrained cyclic shear strength of sandy soils with use of ordinary engineering properties of soils and grounds such as grading properties of disturbed samples and blow counts (N-values) by standard penetration tests. For this purpose, available data of sand sampling, dynamic triaxial tests on undisturbed specimens, N-values by standard penetration tests and gradings were analysed and a correlation among dynamic shear strength, mean diameter D₅₀ and D_γ^*=21√(N/(σ_υ'+0.7)), in which N is the blow counts by standard penetration tests and σ_υ' is the in situ effective overburden pressure in kg/cm², was obtained. This correlation is represented by a simplified equation. Using this equation, approximate dynamic shear strengths of reclaimed and alluvial sandy deposits can be easily estimated from N-values, σ_υ' and D₅₀.

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A method to obtain undisturbed samples of saturated clean sands is presented. In this method a mixture of ethanol and crushed dry ice is circulated through a buried tube to freeze a column of sand which is then pulled out en masse. Laboratory tests and theoretical analyses were conducted to examine factors influencing the quality of the samples with the following results : (1) For sands containing less than 5-percent fines, the expansive strains due to freezing were less than 0.1 percent when the vertical effective stress exceeded about 0.3 kg/cm²; (2) a sequence of freezing and thawing had negligible effects on the strength and deformation characteristics of sands under drained conditions; (3) radial freezing in the field is not expected to cause significant change in the mean principal stress in the sand; and (4) the exterior part of the frozen column of sand nearly retained the in situ density. It is concluded that the proposed method of sampling is an effective means to obtain high quality undisturbed samples of clean sands below ground water table, with a built-in capability to check the quality of the samples by determining the density distribution in radial direction.

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