The stress‐strain response of a granular soil along constant stress increment ratio paths is experimentally investigated for the condition of ${\sigma }_2={\sigma }_3\text{.}$ Since the strains manifested along such paths can be very small, several measures have been developed to improve the accuracy of the strain measurements. A more accurate method of isolating the elastic strain has also been developed to enable reliable determination of plastic strain increment ratio. Test data unambiguously indicate that the elastic response is anisotropic, and the degree of anisotropy increases with the principal stress ratio. The plastic strain increment ratio so deduced from test data is dependent on the stress increment ratio, but can be predicted by combining Rowe's stress dilatancy equation and the energy equation of the Cam‐Clay model. This leads to a new method of predicting the stress‐strain response along such paths. The input parameters can be determined from constant ${\sigma }_3$ tests and constant principal‐stress ratio tests. Excellent agreement with test results is achieved.

An extensive series of undrained triaxial tests were performed on reconstituted samples of Alaskan silts in both the normally consolidated and over‐consolidated state. The results of the investigation show that the pore water pressure increases to a peak and then gradually and continuously decreases with strain. As a result, there is no unique value for the undrained shear strength of a silt. In addition, silt samples are easily disturbed, and their undrained strength is more likely to be seriously affected by disturbance than those of many clays. Sample disturbance is shown to increase the strength measured in IC‐U and AC‐U tests, while decreasing the strength measured in the UU test. Strength anisotropy is as significant in silts as has been reported for some clays. Creep strength loss is small. Results are also presented that analyze the normalized strength behavior of silts.

A constitutive model with a single yield surface has been developed for the behavior of frictional materials, such as clay, sand, concrete, and rock. The model is based on concepts from elasticity and plasticity theories. In addition to Hooke's law for the elastic behavior, the framework for the plastic behavior consists of a failure criterion, a nonassociated flow rule, a yield criterion that describes contours of equal plastic work, and a work‐hardening/softening law. The functions that describe these components are all expressed in terms of stress invariants. The model incorporates eleven parameters for normally consolidated clay that can be determined from simple experiments, such as isotropic compression and consolidated‐undrained triaxial compression tests. A study of the three‐dimensional behavior of remolded, normally consolidated clay has served as a basis for evaluating the capabilities of the model. Overall acceptable predictions are produced for the normally consolidated clay.

A method is described to obtain the static stiffness of the soil under a spread footing by using a hammer impact test. In the first part, the analytical background is presented. In the second part, a test setup is described and the associated results are discussed. The test consists of placing two geophones on the footing, hitting the footing with the instrumented hammer, and recording the force time and velocity time signals. The paper shows that the static stiffness obtained in a load test and the stiffness obtained from the impact test by Fourier transform analysis are reasonably close.

Forced‐haimonic‐vibration tests, using an eccentric‐mass shaker, were conducted on two small but different concrete foundations. One foundation (Cholame 1E), located in central California, consisted of a 4‐in.–(10‐cm‐) thick, 50‐in.‐ (1.27‐m‐) square slab with corner piers embedded in moderately stiff alluvial deposits. The other foundation (Station 6), a 6‐in.‐ (15‐cm‐) thick, $48‐\mathrm{in}\text{.}‐\times 45‐\mathrm{in}\text{.}‐(1.22‐m‐\times 1.14‐m‐)$ rectangular slab, rested directly on softer deposits in the Imperial Valley of southern California. Experimental foundation‐impedance functions, computed from the vibration‐response data, were similar to theoretical predictions for Station 6; however, significant differences were observed between the experimental and theoretical impedance functions for Cholame 1E. These differences probably resulted from overestimation of the shear‐wave velocities of the top layers of soil directly underneath the Cholame IE foundation, and to a lesser extent from the use of a simple embedded disk to model the foundation geometry.

The results are summarized for an experimental program involving over 450 direct shear tests of sand‐polymer interfaces. The interface frictional strength was found to increase with soil density and decrease with the Shore D Hardness of the polymer. The shear strength characteristics were found to vary as a function of the type of sand, but were independent of repeated loading, at least insofar as polyethylene piping and linings are concerned. The shear strength characteristics of a polymer interface can be expressed conveniently as the ratio of the interface angle of friction and the direct shear angle of soil friction, $\delta /{\varphi }_{\mathrm{ds}}^{\prime }\text{.}$ This ratio was relatively constant at 0.55–0.65 along high‐ and medium‐density polyethylene surfaces for different types of sands at various densities. A general model for interface frictional resistance is developed, in which $\delta /{\varphi }_{\mathrm{ds}}^{\prime }$ is related to the Shore D Hardness, $H_D\text{,}$ of the polymer. Limiting conditions for $\delta /{\varphi }_{\mathrm{ds}}^{\prime }$ are defined on the basis of theoretical considerations involving the critical state angle of shear resistance, ${\varphi }_{\mathrm{cv}}^{\prime }\text{.}$ This model allows for rapid evaluation of interface frictional strength and applies to plastic piping, linings, soil strip reinforcement, and a variety of other soil‐polymer systems.

An experimental study of the effects of repeated axial loading on drained uplift capacity of drilled shafts in granular soil is described. The mechanisms that cause changes in drilled shaft side resistance are identified and the effects of initial soil density, shaft‐depth‐to‐diameter ratio, and magnitude of repeated loading are evaluated. Uplift capacity changes are found to depend primarily upon the magnitude of cyclic displacement, and a relationship between the magnitude of cyclic displacement and uplift‐capacity reduction is presented. Critical levels of repeated loading (CLRL) are established, above which shafts fail in uplift and below which failure under repeated loading does not occur. Implications for the design of drilled shafts under repeated axial loading are presented.

The aim of the work described in this paper is to provide a practical procedure for determining the parameters of the cap plasticity model, which is familiar to geotechnical engineers. To this end, a simple procedure relating the cap‐model parameters to those data commonly available from soil tests is proposed. Extensive numerical studies of the behavior and design of the problems frequently encountered in practice are made using a general‐purpose finite element analysis program. These studies confirm the suitability of the proposed procedure and the applicability of the well‐known cap plasticity model to geotechnical engineering problems in general, and embankment problems in particular. The proposed procedure is developed and refined to achieve both simplicity in use and realistic representation of actual condition in practice. It is, therefore, recommended for general use.

A world‐wide review of heavy‐tamping projects indicated that highly organic clays, which due to their secondary compression characteristics may not be amenable to treatment by surcharge and vertical drain installation alone, can nevertheless be stabilized by applying high‐energy impact on installed dynamic replacement (DR) sand columns using a conventional dynamic consolidation plant. Field trials were thus conducted to enforce primary, as well as to negate secondary, compression of in‐situ peaty clay deposits by this form of treatment application, in the course of which dynamic replacement and mixing (DRM) of such soils with sand charges was originally identified as a distinct ground‐improvement mechanism. From the field results and review, it is also perceived that ground‐improvement mechanisms resulting from the application of a wide variety of heavy tamping plant and procedures to soils ranging from granular to highly organic cohesive materials may be generalized on a common physical basis. Further, unique relations may apparently be construed between alternative measures of degree of ground improvement on the one hand, and a collective term incorporating initial soil consistency and standard operational parameters of ground treatment on the other, thereby providing a basis for rational performance design.

A method of designing foundations on slopes of cohesionless material such as sand and normally consolidated clay is described. The method is based on the results of centrifuge tests that were reported in 1988. In order to extend the centrifuge findings out under the slope, the results of other model tests were incorporated into the design procedure which is outlined. Thus the method presented here is based on physical tests rather than on theory. One innovation is that the bearing capacity of a footing on or near a slope is rated as a percentage of the capacity that the same footing would have on the surface of level ground. This means that local experience can be used to determine the safe capacity of the reference, level‐ground footing. This capacity can then be corrected to take into account the proximity of the slope. A second innovation is that the designer need not correct for footing size, since the tests were run on footings of reasonable scale. The method is straightforward and simple to use, and covers the design geometries that are most likely to be met in practice.