Statistical models are developed to express the probability of liquefaction as a function of earthquake load and soil resistance parameters. Results are obtained based on a catalog compiled for this study, which consists of 278 cases of liquefaction/nonliquefaction occurrences. A method of binary regression is used to derive four models recommended for use in assessment of liquefaction probability. Two of them use the cyclic stress ratio (Seed and Idriss 1971) as the earthquake load parameter; the other two use, as load parameters, explicit functions of earthquake magnitude and distance, similar to the function proposed by Davis and Berrill (1981). All four models measure liquefaction resistance through the corrected/normalized SPT $(N_1{)}_{60}$ value. Recommendations for practical implementation are provided, and comparisons are made with other methods of liquefaction analysis.

Liquefaction of loose, saturated sands may be caused by cyclic or static (monotonically increasing) undrained loading. Most previous studies of static liquefaction behavior have emphasized liquefaction susceptibility and the behavior of liquefied soils. An experimental investigation is undertaken to evaluate the stress conditions required to initiate liquefaction and the influence of various parameters on those stress conditions. The static liquefaction resistance, denned as the shear stress increase under undrained conditions required to initiate liquefaction, is observed to increase with increasing relative density and confining pressure, and to decrease dramatically with increasing initial shear stress level. At high initial shear stress levels, initiation of liquefaction is observed to result from increases in shear stress under undrained conditions of only a few percent of the initial shear stress. The distinction between the initiation and the effects of liquefaction is discussed, and an expression for a factor of safety against the initiation of liquefaction is proposed.

Centrifuge model tests were conducted on models of flexible shallow tunnels in dry sand subject to blast loading from nearby highenergy explosives. Experiments were conducted with varying centrifugal accelerations (from 1 g to 97 g on 2.5‐5‐cm‐diameter model tunnels made of thin brass and aluminum sheet. Buried, 1/2‐g and 1/16‐g pentaerythritol tetranitrate (PETN) explosive charges were detonated at a distance of 0‐2 diameters from the tunnels during centrifugation. It appears that for flexible tunnels which are exposed or nearly exposed by the crater, significant damage to the tunnel occurs during crater excavation. The intense flow which occurs in the soil near the crater appears to be the major cause of distortion of the tunnel and the shock wave itself is often less significant. The distance from the tunnel to the crater appears to be a more significant factor than the distance from the tunnel to the charge in causing damage to flexible tunnels. Since gravity influences the cratering process, and consequently influences the soilstructure interaction, it is important to conduct scale‐model tests of this type of event on a centrifuge. The centrifuge scaling laws were verified by conducting modeling of models tests using 1/97‐ and 1/48.5‐scale tests. Cratering efficiency is also compared to that measured by other researchers with reasonable agreement.

Better grouts have become necessary with increases in the size and complexity of ground anchors. This is because large anchors, such as those now used for stressing dams to their foundations, have closely packed hardware that makes it difficult to slide the grout tubes out as the grouting proceeds, as was previous practice. Because the tubes are stationary, the grout emerging from them has to travel considerable distances, and as the grouting progresses, fresh grout is compelled to either push through earlier‐placed grout, or to push that earlier grout bodily upward before it. The mechanisms of these alternatives were investigated in large scale tests. To ensure void‐free grouting, grouts have been developed with an unusually low water content. The testing for these quite unexpectedly found that large voids can result from some commonly used expansive additives, which evidently should be regarded with caution for this type of anchor.

A method of predicting pile‐group settlements is presented herein for cases in which the piles are held together by means of a rigid cap. Piles in the group are assumed to be of the same material, length, and diameter. Settlement influence and interaction factors are obtained using a finite element code, modeling the pile as a hollow cylindrical insert in the interior of a homogeneous, linear, elastic, isotropic halfspace. These factors are tabulated and can be used with the results of individual, full‐scale, pile load tests to provide a very effective means of estimating pile‐group settlements. Shaft and point loads are treated independently when applying the method, thus allowing for simulation of implicitly variable shaft and point load ratios during loading. Uniform shaft load distributions are assumed, but other distributions can be considered as well. Few parameters are needed to apply the method, which therefore retains the simplicity of existing elastic methods. A full‐scale, pile‐group load test reported in the literature is analyzed to show the reliability of the proposed method. Results are presented that indicate excellent agreement between predicted and measured values.

The results of centrifuge tests for bearing capacity of circular footings are used to verify the bearing capacity predictions using Hansen's equations with interpretations by Meyerhof and De Beer. The correlation with De Beer's method, which accounts for the variation of friction angle ϕ with normal pressure, is very good. An alternate proposal, using a constant ϕ and an intercept c at zero normal pressure that best fit the failure envelope in the range of interest, also gives a good correlation with the data. The proposed method does not require the iteration procedure that is required by Meyerhof and De Beer. The results are applicable to shallow circular foundations in dense sand where general shear failure is the dominant mechanism. Modeling of models tests were conducted to verify the centrifuge scaling laws over a range in scale factors. The good agreement of modeling of model tests shows that the centrifuge is a useful tool for modeling bearing capacity problems.