The finite element method has been used increasingly in recent years to simulate the process of excavation. When the soil is linearly elastic, the results of excavation must be independent of the number of steps in the cutting process. However, recent experiences with finite element analyses indicate that the results of actual computer runs can be seriously in error and, in particular, the displacements at the top of a vertical cut can appear to depend on the number of steps of cutting into an elastic soil. It is shown that these errors are caused largely by the inability of the finite elements to model adequately the stress gradients near the toe of the excavation. A modified procedure is recommended, and it is emphasized that such simulations of excavation should be done in as few steps as possible.

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The analysis and application of repeated load test results of soils are approached from the point of view of improving the design of subgrades. The soils dealt with are unsaturated sandy loam and sandy clay loam. First, the characteristics of soils under repeated load are investigated by performing a simple repeated load test on the soils; next, the fatigue problem of soils are studied; thirdly, several instances of introducing the test results to the design problems of subgrades are described. Consequently, the results are found applicable to the design and construction of the subgrade.

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A method is presented for determining the complete behaviour of either a single or double, homogeneous elastic layer, with an underlying rigid base and arbitrary vertical loading. The method is readily programmed for a computer and is both accurate and rapid.The axisymmetric point load solution for a half-space is used together with a series of spherical harmonics and biharmonics to satisfy the layer boundary conditions. The series coefficients are determined by the multiple Fourier method. Expansion into polynomials in radius and depth is then effected, enabling analytic integration of the stresses and displacements for both the half-space solution and the polynomials, over a circular sector. The sector method is then used for arbitrary loading.Results are presented for the constant depth single layer with a rough rigid base, for a surface point load, and uniform and linear square surface loading. Accuracy is satisfactory for loading and point of interest within a cylindrical region of width/depth ratio, 3, for point loading and a ratio of 3.5 for uniform and linear loading.

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Based on a critical review of the available data in creep tests previously published by many investigators, a new concept of flow envelope is presented and substantiated for normally consolidated clays. It is shown that the flow envelope is expressed by a simple equation irrespective of the type of clays, water content, drainage condition and stress history. This fact provides a clue from field observations for more proper understanding of the dividing line between the secondary compression-type deformation and the plastic flow-type deformation. A flow envelope for a lightly overconsolidated clay is also obtained, which suggests that even a moderate overconsolidation is effective in suppressing the rate of the subsequent flow.In order to elucidate the loading path dependency of stress-dilatancy relationship, a series of drained incremental creep tests were performed on a normally consolidated clay. The results indicate that while a linear relationship between volumetric strain and deviatoric strain holds for each increment of sustained loads, its slope is larger than that predicted by a theory of quasistatic equilibrium but it is finally reduced to the value associated with an equilibrium state as the increment value of effective stress ratio decreases.

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The shear behaviour of granular materials at moderately high pressures up to 1600 lb/sq.in. was studied in drained triaxial tests. Three angular sands were artificially prepared with the same initial grading. The materials used were aluminum oxide, quartz and limestone, in order of decreasing particle strength. Enlarged lubricated end platens were used to achieve more uniform crushing and stress-strain distribution throughout the sample. It is shown that the stress, strain, volume change behaviour are primarily governed by particle degradation. The effective angle of friction decreases with increase in confining pressure but the rate of reduction is diminished with decrease in particle strength, with the result that the φ' is actually higher for a weak-grained material than a strong-grained material. It is also important to distinguish between the two points of zero dilatancy rate for the interpretation of test results at high pressures.

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The effects of time duration of the confining pressure and stress-history patterns were studied through resonant column tests of soil samples. For each soil the dynamic shear modulus obtained at small shearing strain amplitudes was the quantity evaluated as the testing conditions were changed.Under uniform confining pressures an increase in shear modulus occurred which was approximately linear with log time after about 1000 minutes of pressure application. This rate of shear modulus increase per log cycle was expressed as a per cent of the numerical value of the shear modulus at 1000 minutes, to minimize the influence of the pressure magnitude for each test. For soils with median grain size larger than about 0.04 mm the per cent increase in shear modulus per log cycle was about 3% or less. For dry and saturated samples of kaolinite, this increase averaged about 6% to 13%. The effect of overconsolidation was to reduce slightly this rate of shear modulus increase per log cycle.Soils with median grain size of 0.04 mm or greater showed little change in the small amplitude shear modulus as the time of applied confining pressure increased, or little influence of previous preconsolidation. For finer soils (D₅₀«0.04 mm) the effects of time of loading and of preconsolidation were significant. Consequently, extrapolation of laboratory shear moduli of fine-grained soil to field applications requires careful study.

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Expansive soils pose a problem to the construction engineers. At present there is no universally accepted simple procedure for identifying these soils. The authors present in this paper a method for identifying expansive soils from its liquid limit, plasticity index and shrinkage index values. Test results on fifty soils from Tamil Nadu and the Deccan Trap regions and the data taken from other research publications are analysed and a comparison is made between the different methods to demonstrate the reliability and simplicity of the proposed method over the other methods available to the practising engineers.

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