Response of individual piles to externally applied loads is one of the most complex soil-structure interaction problems in the field of foundation engineering. For any realistic analysis of this problem, it is essential to take into account both the elastic and plastic properties of the soil, as both these states occur along the embedded length of the pile. Herein, analysis and results are presented for the problem of axially and laterally loaded piles, taking into account elasto-plastic nature of the soil for both cohesive and cohesionless soils. The results indicate that the flexural behaviour of laterally and axially loaded pile in an elasto-plastic soil is considerably influenced by type of variation of plastic resistance, soil modulus variation and the boundary conditions at the top.

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In the soil surrounding a laterally loaded pile, there are two zones; the top plastic zone where the soil yields once the ultimate resistance is reached and the bottom elastic zone where the soil reaction is proportional to pile deflection. In this paper, an analysis is presented for an axially and laterally loaded, uniformly tapering circular pile embedded in sand, taking into account the plastic behaviour of the soil near the ground surface. The differential equations governing the pile deflection at the top plastic zone and the bottom elastic zone are transformed to non-dimensional form and solutions are obtained. Free-free and fixed-free end conditions are considered. Top deflection coefficients and maximum moment coefficients are plotted against lateral load factor for different axial load factors and taper. For given axial and lateral loads, the top deflection and the maximum moment are found to increase with taper. The fixity at the top considerably reduces the deflection at the top. A numerical problem is worked out to illustrate the use of the plots to obtain the top deflection and the maximum moment.

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In the paper are shown the expressions for calculating stresses and displacements beneath the rigid rectangular foundation resting on an elastic isotropic layer of finite thickness, underlain by a rigid base. The contact between the compressible layer and rigid base is assumed to be perfectly rough.Using Fourier's series, stresses and displacements have been determined for the ratio H/B=1.0; 2.0; 3.0 and 5.0 (where H is the thickness of the compressible layer), for the ratio L/B=1.0; 2.0 and 5.0 (where L and B are the dimensions of the foundation) and for the Poisson's ratio μ=0.15; 0.30 and 0.45.

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The upper bound technique of limit analysis is used to obtain rationally founded solutions to the active and passive limit earth pressures for a cohesionless soil retained by a rigid wall of varying roughness. These results are found to favorably agree with known solutions including those obtained by slip-line methods. The formulation is based on a treatment of the soil as a perfectly plastic medium obeying the Mohr-Coulomb yield condition. Several failure mechanisms composed of rigid bodies and radial shearing zones are studied. A new circular shearing zone for finite soil friction is also developed. Considerable solution improvement for passive pressures on rough walls is obtained. The necessary formulation for cohesive soils and surcharge loading is also given.

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From statistical analyses of accumulated data on dynamic characteristics of various soil deposits measured by means of seismic exploration, it has been found that shear moduli for small shear strain level are well correlated with N-values of the standard penetration test, and that their interrelation may be expressed by a simple, approximate Eq. G=1200N^0.8 (tons/sq. meter) regardless of soil types and depths from the ground surface. A few matters related to dynamic Poisson's ratios of soil deposits are also discussed from a statistical viewpoint.

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In order to estimate the active earth pressure and the earth pressure at rest against the walls during earthquake, the authors carried out the tests using a large scale vibrating soil bin in laboratory. The resultant force due to the oscillating earth pressure, its applied point and the angle of wall friction were measured during the wall displacement. The active earth pressure during earthquake and its applied point are derived based on the measured values of the earth pressure of which angle of wall friction is fully mobilized for the maximum inertia force. This equation can be applied to the vertical or inclined retaining walls with any backfill sands. The equations for earth pressure at rest are also derived.

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