A method has been developed for the estimation of resilient modulus of compacted fine‐grained subgrade soils. The method takes into account the influence of soil physical state, stress state, and soil type. The effect of soil physical state is quantified by combinations of two equations relating resilient modulus to moisture content. One equation is for paths of constant dry density and the other is for paths of constant compactive effort. The effect of stress state is determined by equations relating resilient modulus at optimum moisture content to deviator stress so that the equation parameters represent the effect of soil type and its structure. Means to estimate the resilient modulus at optimum moisture content are suggested in the absence of actual test data. Examples of applications of this method showed that it is simple and versatile and also gives consistency between predicted resilient modulus and resilient modulus test results.

Failure envelopes of sands are often considered to be nonlinear depending both on relative density and stress level. Triaxial tests that were performed on clean alluvial‐quartzitic Zbraslav sand were used for analyzing the form of the failure envelope. In addition to relative density and stress level, the stress path (tests with constant‐cell pressure were compared with tests with constant‐mean‐stress level) has been found to affect the shear resistance as well. Only tests with constant‐mean stress produce nonlinear‐failure envelopes. Up to the peak‐stress difference, no shear bands were observed. Rough platens were used to simplify the procedure since the specimen's restraint was found not to affect the shear resistance for diameter to height ratio 1:2. The writer uses the percolation theory to provide the physical interpretation of the experimental results.

In response to an urgent need for field data from instrumented liquefaction sites, the U.S. Geological Survey in 1982 selected and instrumented a site in southern California called the Wildlife site. Two accelerometers (one at ground surface and one at a depth of 7.5 m) and six electrical pore‐pressure transducers (five in a liquefiable silty sand layer) were placed at the site. The November 1987 Superstition Hills earthquake triggered sand boils and the desired instrumental response by generating excess pore‐water pressure that approximately equaled the initial effective overburden pressure. These records are the first from a field site to trace ground motions and pore pressures through the entire liquefaction process. Because pore pressure continued to rise after most of the seismic energy had propagated through the site, questions about the fidelity of the pore‐pressure records have been raised. Because of the importance of the Wildlife records, we reexamine pertinent aspects of the instruments and their placement, review their 1987 response, evaluate and respond to criticisms by Hushmand et al. (1992a, 1992b), and examine analyses of the records by other investigators that are pertinent to an evaluation of the fidelity of the piezometer records. This review concludes that no data or analyses have been developed that convincingly demonstrate that the pore‐pressure piezometers responded incorrectly. Conversely, an analysis by Zeghal and Elgamal (1994) provides strong evidence that the piezometers responded with a high degree of fidelity.

The surface and downhole accelerations, and pore‐water pressures recorded during the 1987 earthquakes at a site in the Imperial Wildlife Management Area (Imperial County, Calif.) are used to obtain direct estimates of the average seismic shear stress‐strain and effective stress‐path histories. These histories provide valuable insight into the site seismic behavior during liquefaction and associated loss of soil stiffness. As the pore pressure increases due to seismic excitation, site stiffness is found to gradually decrease. During the high‐pore‐pressure phase, site behavior is characterized by cycles of large shear strain and very small shear stress. At these large strains, evidence of hardening response, possibly due to a dilative‐type soil behavior, is observed. The results of this study demonstrate that acceleration and pore pressure histories recorded by downhole arrays represent a valuable direct source of information on site response during seismic excitation.

The $p‐y$ method of analysis models nonlinear behavior, and is an effective method of designing deep foundations subjected to, lateral loads. Deflections and bending moments calculated using $p‐y$ analyses have usually been found to be in good agreement with field measurements. This paper describes a method of analysis, the characteristic load method (CLM) that is simpler than $p‐y$ analyses, but that closely approximates $p‐y$ analysis results. The method uses dimensional analysis to characterize the nonlinear behavior of laterally loaded piles and drilled shafts by means of relationships among dimensionless variables. The new method is simple enough for use by manual calculation, and it can also be adapted for computer use. Lateral deflections and maximum bending moments calculated using CLM have been found to be in good agreement with values measured in field load tests.

Current procedures for designing groups of piles for lateral loading require the use of a computer or extensive manual computations. This paper presents a simple method (the group amplification procedure) for estimating pile group deflections and maximum bending moments based on the theories of Poulos, and Focht and Koch. The method is applicable to groups of drilled shafts as well as groups of piles. Group lateral deflections and the maximum bending moment in the most severely loaded pile in the group are estimated by multiplying the values for single piles by amplification factors (which have values larger than unity). Lateral deflections and maximum bending moments calculated using the group amplification procedure have been found to be in good agreement with values measured in field load tests.

A total stress‐based bounding surface plasticity model for clays is developed to accommodate multiaxial stress reversals. The model is constructed based on the idea of a vanishing elastic region undergoing pure translation inside a bounding surface, and an interpolation function for hardening modulus which varies with stress distance of the elastic region from the unloading point. Central to the development of the model are the general criteria for loading and unloading, which are phrased based upon the simple argument that with continued loading the hardening modulus should decrease monotonically with deformation. Combined with numerical integration of the elastoplastic constitutive equations in a form suitable for a robust computer implementation, the model is applied to cohesive soils undergoing undrained stress reversals and cyclic loading. With a suitable choice of the interpolation function for the hardening modulus, it is shown that existing one‐dimensional nonlinear laws for soils can be replicated, such as the hyperbolic, exponential, the Davidenkov, and even the Ramberg‐Osgood models. Specifically, the appropriateness of the exponential hardening function for cohesive soils is investigated and its parameters determined for some clays and silts for use in dynamic soil‐structure interaction modeling.

Earth‐pressure problems are of great interest in geotechnical engineering and closed‐form solutions for evaluating the active‐earth pressure are widely used in the design of retaining structures. The note presents a closed‐form solution based on the Coulomb‐failure wedge for the case in which a surcharge is applied a certain distance from the wall. This allows the earth pressure to be evaluated according to the actual‐site conditions and to avoid uneconomical design. The basic assumptions are that the failure surface is a plane; the soil is homogeneous, dry, and cohesionless; and the extent of the surcharge is sufficiently large to ensure that the failure plane intersects it at the ground surface. Indications are then given to ensure the compatibility of the solution with the real‐site conditions.

The main objective of this investigation was to understand the strength development of clays below fusion or vitrification temperatures of 900°C. The other objective was to establish threshold temperatures to produce a satisfactory construction material from clayey sediments from the Western Beaufort Sea for shore protection of artificial islands with minimum expense of thermal energy. Studies were, therefore, conducted using kaolinite, bentonite, and a clayey sediment from the Beaufort Sea. Unconfined-compressive-strength tests were conducted on clay samples heat treated from 110 to 700°C. Furthermore, to understand the factors responsible for strength-development-thermogravimetric studies and pore-size analysis, using mercury porosimetry, were also conducted. A gradual increase in strength was obtained with an increase in firing temperature. However, substantial and permanent increase in strength occurred only after dehydroxylation of all the clays studied; Clay samples heated to temperatures above dehydroxylation became resistant to disintegration upon immersion in water. Results indicate that the clayey sediments from Western Beaufort Sea have to be heat treated to about 600°C to produce granular material for use as a fill or shore-protection material for artificial islands.

This technical note examines the results of a nonlinear, finite‐strain consolidation analysis of a clay layer subjected to underdrainage at its base. It is shown that due to the nonlinearity of the soil properties the steady‐state pore‐water pressure cannot be defined until the end of consolidation. It is further shown that the steady‐state reference pore‐water pressure at the beginning and end of consolidation are different when the clay layer is loaded by a surcharge. The use of the excess pore‐water pressure as the dependent variable in a consolidation analysis is discussed.