Presented are the results of an experimental research program involving centrifugal model tests on a column of sand confined by a stack of teflon coated aluminum rings with a latex membrane between the sand and the rings. Dynamic centrifugal model testing was performed in a 1 m radius Schaevitz centrifuge using a piezoelectric shaker. A column of Monterey 0 grade sand contained in a stacked‐ring apparatus modelled a sand layer. The sand layer was instrumented with pore pressure transducers at different depths and accelerometers at the base and top. The model was excited at the base with sinusoidal motions of various amplitudes and the excess pore water pressures and the ground surface accelerations were monitored. The principal objectives were to study the generation and dissipation of excess pore water pressures, and to estimate the threshold peak ground surface acceleration, and the threshold shear strain necessary for the initiation of excess pore water pressure. The influence of prior strain history on the generation of pore water pressure was an additional objective of this study. The study showed that the measured time history of excess pore pressure generation and pore water pressure distribution with depth compared favorably with that predicted by the currently available numerical procedures using dynamic test results obtained on small elements of homogeneous sand. The study also showed the significance of the initial prior strain history on pore pressure development and the accuracy of the peak threshold acceleration and shear strain estimated from dynamic tests on small elements of homogeneous sand in cyclic triaxial tests.

The semi‐analytical solution of the dynamic behavior of vertical pile groups is presented. The solution accounts for the pile‐soil‐pile dynamic interaction and is based on modeling the soil as a plane strain continuum and the piles as a set of finite elements. The method is generally enough to model any pile group geometry in a layered soil. The proposed method is simple since it needs no special soil modeling, accurate since its results compared well with the results of finite elements method, and cheaper to use than the finite element method. Some case studies are presented which show that the dynamic pile‐soil‐pile interaction is important for longer distances between the piles than the static case. It is shown also that correction factors due to dynamic pile‐soil‐pile interaction is frequency dependent.

Finite element analysis of a sewer tunnel crossing over existing sub‐way tunnels in New York was performed. The clearance between the sewer tunnel and the subway tunnels was very small and the purpose of the finite element analysis was to evaluate the influence of the sewer tunnel construction on the subway tunnel liner forces. The construction of the subway tunnels and the process of construction of the sewer tunnel were simulated in the analysis. The paper describes the field condition and the analysis, and presents comparisons between the analysis results and the field measurements.

Direct shear tests were run on a dry sand reinforced with different types of fibers. Both natural and synthetic fibers plus metal wires were tested. Experimental behavior was compared with theoretical predictions based on a force equilibrium model of a fiber reinforced sand. Test results showed that fiber reinforcement increased the peak shear strength and limited post peak reductions in shear resistance. The fiber reinforcement model correctly predicted the influence of various sand‐fiber parameters through shear strength increases that were: (1) Directly proportional to concentration or area ratio of fibers; (2) greatest for initial fiber orientations of 60° with respect to the shear surface; and (3) approximately the same for a reinforced sand tested in a loose and dense state, respectively. The findings of this study are relevant to such diverse problems as the contribution of roof reinforcement to the stability of sandy, coarse textured soils in granitic slopes, dune and beach stabilization by pioneer plants, tillage in root permeated soils, and soil stabilization with low modulus, woven fabrics.

A brief outline is given of the basis of analysis used in two computer programs, PIGLET and DEFPIG, for analysis of pile group response. A comparison of the capabilities of each program is presented and then a parametric study is made of a six‐pile group to illustrate the similarities and differences between the two programs. Two series of field tests on groups of piles are then analysed by DEFPIG and PIGLET, and it is shown that the predictions from each are consistent and in generally good agreement with the field data. The comparisons suggest that each program may be used with confidence for practical problems, particularly in conjunction with single pile load test data.

A first‐order second‐moment method is proposed to quantify uncertainty about steady‐state pore pressures originating in random spatial variability of soil permeabilities. A Bayesian framework for systematic interpretation of piezometer observations is set out, which allows updating of the pore pressure field and, therefore, of geotechnical performance predictions. A probabilistic quantification of the observational method is attempted, so that probabilities assigned to different hypotheses (states of nature) regarding seepage can also be updated on the basis of piezometer readings. Application of the approach to the decision problem of sequential instrument location is suggested. An example illustrates the versatility of the proposed methodology.

An attempt is made to clarify certain aspects of the modeling of behavior of particulate materials. The issues are presented in terms of an incremental Hooke's law. The formulation accounts at least partially for the effects of inherent and stress‐induced anisotropy and for the effects of direction and rotation of the stress increment vector. Arguments are presented to indicate that plane strain in particulate materials is approximately two‐dimensional, with in‐plane normal stresses and longitudinal strains uncoupled from out‐ofplane stress. Particulate materials exhibit stress‐path‐induced anisotropy as well as stress‐magnitude‐induced anisotropy. A given particulate material may be cross‐anisotropic in triaxial compression but two‐dimensional in plane strain. Hooke's law is used as a vehicle for presentation of the issues because of its familiarity to geotechnical engineers and its continued use in practice.

The ultimate bearing capacity of rigid piles and pile groups in sand has been determined under various combinations of eccentricity and inclination of the load varying from the vertical to horizontal directions. The results of load tests on single model piles and free‐standing groups are compared with theoretical estimates. The influence of eccentricity and inclination of the load on the bearing capacity can be represented by simple interaction relationships between the ultimate loads and moments and between the axial and normal components of the ultimate load. The effect of a pile cap resting on the soil in piled foundations is examined on the basis of previous theory and model test results.

The concept of utilizing preplaced “quarry run rock” (unprocessec rock blasted at a quarry) as a retaining wall for large excavations in soft soils is described. Various configurations of rock placement are presented and con sidered to show that a shallow slope failure can be prevented by placing suf ficient rock at the toe and a deep base failure can be prevented by either con structing a keyway or by placing rock at the toe of the slope. The rock revetment must be constructed prior to the excavation in a trench that is sta bilized by flooding with water. Where there is sufficient area available, the rod revetment appears to be a fully effective solution and much more economica than other types of retaining structures.

Sands that did and did not liquefy at two sites during the 1979 Imperial Valley, Calif., earthquake $(M_L=6.6)$ are identified and their properties evaluated. From cone soundings, stratigraphy was determined, soil types and properties estimated, and optimal locations for samples and SPT tests selected. Samples were used to classify sediments and to identify modes of deposition. SPT tests were used to evaluate liquefaction susceptibility. Loose fine sands in an abandoned channel liquefied and produced sand boils, ground fissures, and a lateral spread at the Heber Road site. Evidence of liquefaction was not observed over moderately dense over‐bank sand east of the channel nor over dense point‐bar sand to the west. Standard analyses predict that both the channel and the over‐bank sands are liquefiable, but that the point bar is resistant. At the River Park site, a layer of loose floodplain silty sand overlies a layer of clay, which in turn overlies a thick bed of sand that increases in density with depth. Parts of both the upper silty sand and lower sand liquefied and produced hundreds of sand boils. Standard analyses predict that the looser parts of both layers are liquefiable.

The evolution of a simplified procedure for evaluating the liquefaction potential of sand deposits using data obtained from standard penetration tests is reviewed. Field data for sites which are known to have liquefied or not liquefied during earthquakes in the United States, Japan, China, Guatemala, Argentina, and other countries are presented to establish a criterion for evaluating the liquefaction potential of sands in Magnitude 7‐1/2 earthquakes. The results of this study are then extended to other magnitude earthquakes using a combination of laboratory and field data. Available information on the liquefaction resistance of silty sands is also reviewed and a simple procedure for considering the influence of silt content is proposed. A method is presented for using the field data to evaluate the possible magnitude of pore water pressure generation in sands and silty sands which remain stable during earthquake shaking. Finally, the applicability of other in situ field tests, such as the static cone penetrometer, shear wave velocity, and electrical measurements for evaluating the liquefaction resistance of soils is examined.