An efficient method of analysis has been developed to determine the steady‐state dynamic response of vertically loaded piles and pile groups embedded in a soil stratum in which the stiffness increases linearly with depth. The piles have been represented as compressible columns and the soil as a hysteretic semi‐infinite medium. The results of the analysis have been plotted in nondimensional form to demonstrate the effects of key nondimensional parameters on the vertical response of the pile‐soil system. From the results of analyses of two pile groups, dynamic interaction factors have been calculated. These factors are very different from the interaction factors for homogeneous soils, particularly if the piles are widely spaced. These interaction factors reveal that piles in groups are subject to out‐of‐phase motions, which may result in substantially reduced pile group settlements at certain frequencies. Illustrative results for four and nine pile groups are given, as well as a practical design example.

A new method is presented for analysis of the potential for triggering liquefaction, i.e., a flow slide, in liquefiable soil masses. The method is based on the principle of steady state deformation. In conventional mine tailings disposal operations, the tailings are pumped as a water suspension into extensive flat containment ponds. These ponds generally are formed by construction of large tailings dams. However, if the tailings are thickened substantially before discharge, the tailing slurry will form a sloping deposit. Maximum slope angles of 3.5° are normally recommended. Use of thickened tailings is less costly and has much less environmental impact than conventional tailings because tailings dams and their associated slime ponds are eliminated. In this paper, the resistance to liquefaction due to earthquakes of a proposed bauxite tailings deposit placed at a 2.9° slope is analyzed. The water content of the thickened tailings is high enough to make them susceptible to liquefaction even when placed at such gentle slopes. However, due to the clay content and thixotropic nature of these tailings, earthquakes that induce 0.1 g peak ground acceleration do not cause enough strain to trigger liquefaction.

Drained and undrained cyclic torsional simple shear tests are conducted for saturated Ottawa sand with and without initial static shear applications. It was found from the experiment that when the tests were conducted under uniform cyclic shear strains, both pore water pressure generation in undrained conditions and the volume changes in drained conditions were affected very little by the level of the initial static shear applications. The strain method, which uses shear strain parameters as determinative parameters, has been proven to be very useful for liquefaction and cyclic volume change analyses.

The measured coefficient of consolidation, $c_{\upsilon }\text{,}$ can have a substantial degree of variation even in a uniform clay layer. This paper, through a probabilistic analysis, examines the variability of one‐dimensional consolidation solutions. Both the single layer and the multilayer models are evaluated. In the probabilistic analysis, the adequacy of a gamma distribution model for $c_{\upsilon }$ is tested using experimental data. Then both the method of moments and the Monte Carlo method are used to develop solutions for one dimensional consolidation. The results are discussed in terms of confidence level with examples to demonstrate the variability of the solution of consolidation analysis.

The purpose of this paper is to clarify the meaning of the values of standard penetration resistance used in correlations of field observations of soil liquefaction with values of $N_1$ measured in SPT tests. The field data are reinterpreted and plotted in terms of a newly recommended standard, $(N_1{)}_{60}\text{,}$ determined in SPT tests where the driving energy in the drill rods is 60% of the theoretical free‐fall energy. Energies associated with different methods of performing SPT tests in different countries and with different equipment are summarized and can readily be used to convert any measured N‐value to the standard $(N_1{)}_{60}$ value. Liquefaction resistance curves for sands with different $(N_1{)}_{60}$ values and with different fines contents are proposed. It is believed that these curves are more reliable than previous curves expressed in terms of mean grain size. The results presented are in good accord with recommended practice in Japan and China and should, thus, provide a useful basis for liquefaction evaluations in other parts of the world. Finally, suggestions are made concerning the significance of the term “liquefaction” as it is often used in conjunction with field evidence of this phenomenon.

Two broadly based empirical strength criteria have recently been proposed for intact rock. The first, which applies to intact rock and rock masses was presented by Hoek and Brown in 1980. The second, which applies to all intact geomechanical materials ranging from slightly overconsolidated clays to hard rocks, was presented more recently by the writer. It is demonstrated that the two different criteria predict essentially the same variations in strength when each is applied to the material of common interest, namely relatively hard intact rocks.