Mexico City's strong earthquake of September 19, 1985, induced many evident seismic phenomena at the ground surface and building foundations because of the seismic wave action. The paper is devoted to report briefly some of the studies made by the author because of this unfortunate phenomenon. For better understanding the seismic action the geotechnical environment of Mexico City is presented and a seismic record is analyzed. A method to estimate the seismic pore water pressure is given. Instrumentation designed and used by the author is presented along with investigation of the necessary dynamic parameters to be applied in the analysis of seismic wave action. The malfunction of friction piles is discussed to visualize the importance of the seismic pore water pressure in the reduction of the shearing strength. In summary, the paper is intended to stress the importance to investigate the effects of the seismic wave action close to the ground surface and building foundations in Mexico City.

The main objective of this work is to examine the effect of nonlinear soil behavior on the axial and lateral response of piles to monotonic and cyclic loading with a view towards developing simplified, yet realistic models for representing pile‐soil‐pile interaction effects. The specific role of pile‐soil slippage and separation, and the overall nonlinear soil behavior on the response of single piles and pairs of piles is studied by means of a three‐dimensional finite element elastoplastic model that includes interface elements for representing slippage and pile‐soil separation. Numerical results indicate that material nonlinearity can significantly affect pile and soil response. Pile‐soil slippage is dominant under purely axial loading, while for lateral loads pile‐soil separation and generalized inelastic soil deformation are the crucial factors. In fact, ignoring these sources of nonlinearity can lead to greatly overestimating the amount of interaction between piles. Guided by the results of this work, a simplified model, consisting of coupled, inelastic supported one‐dimensional piles is developed in the companion paper.

The main objective of this work is to use the experience gained from a three‐dimensional parametric study presented in a companion paper to develop a simplified model that will reproduce the main nonlinear features of the behavior of single piles, as well as the interaction between a pair of piles. Hence, guided by the results of that parametric study, a simplified model consisting of coupled, inelastically supported one‐dimensional piles is developed and presented herein. This model takes into consideration slippage and separation between the piles and the soil, as well as the overall inelastic soil behavior including degradation. The validity of the proposed model is assessed by an extensive comparison with numerical results from the more accurate three‐dimensional study, as well as with results from experimental field tests. Close agreement is observed between these results and the predictions from the simplified model. This represents an essential step towards a simplified, yet realistic, method of analysis for general pile groups.

Recent studies suggest that diffusion may be an important, if not dominant, mechanism of contaminant transport through waste containment barriers. This paper represents the first of two papers pertaining to the measurement of diffusion coefficients of inorganic chemicals diffusing in saturated soil. In this paper, both steady‐state and transient equations describing the diffusive transport of inorganic chemicals are presented. Several factors affecting diffusion coefficients are identified. A method for measuring diffusion coefficients for compacted clay soil is described. The definition for the diffusion coefficient for diffusion in soil (known as the effective diffusion coefficient, $D^{*})$ is shown to vary widely. In general, variations in the definition of $D^{*}$ result from consideration of the different factors that influence diffusion of solutes in soil and the different ways of including the volumetric water content in the governing equations. As a result of the variation in the definition of $D^{*}\text{,}$ errors in interpretation and comparison of $D^{*}$ values can result if the appropriate definition for $D^{*}$ is not used.

The effective diffusion coefficients, $D^{*}\text{,}$ of three anions (${\mathrm{Br}}^{-}\text{,}$ ${\mathrm{Cl}}^{-}\text{,}$ and $I^{-})$ three cations ${\mathrm{Cd}}^{2+}\text{,}$ $K^{+}\text{,}$ and ${\mathrm{Zn}}^{2+}$ diffusing in two compacted clay soils, kaolinite and Lufkin clay, are measured. The ions are contained in a simulated waste leachate. The effects of molding water content and method of compaction on the measured $D^{*}$ values are evaluated for kaolinite. The calculated $D^{*}$ values varied between $4\times {10}^{-10}{m}^2/s$ and $2\times {10}^{-9}{m}^2/s$ and, based on the results for chloride diffusion in kaolinite, are relatively insensitive to molding water content and compaction method. The measured $D^{*}$ values for ${\mathrm{Cl}}^{-}$ and ${\mathrm{Br}}^{-}$ in kaolinite are in excellent agreement with previous studies, but the $D^{*}$ values for the cations are relatively high. High $D^{*}$ values for the cations are attributed to nonlinear adsorption behavior at relatively high concentrations and to the possibility of chemical precipitation of the heavy metal species (${\mathrm{Cd}}^{2+}$ and ${\mathrm{Zn}}^{2+})\text{.}$ Also, $D^{*}$ values determined from reservoir concentrations typically are higher than $D^{*}$ values determined from soil concentration profiles.

This paper summarizes the results of a study conducted to improve design procedures for vertically loaded H‐piles in cohesionless soils. Included in the study is the examination of several procedures for estimating residual loads and assumptions concerning the plugging phenomena that may occur between the flanges of an H‐pile. Data obtained from full‐scale load tests reported in the literature are used to develop the improved design procedures. The improved procedures include a procedure for estimating ultimate bearing capacity and a procedure for developing load‐versus‐settlement relationships for H‐piles in sand. Load‐test results from two H‐piles that are not part of the data base are included to demonstrate the use of the improved design procedures. The predictions made for these two H‐piles using the improved design procedures are closer to the measured load‐settlement values than predictions made using existing design methods.