A numerical procedure is presented for the settlement analysis of group piles that penetrate an upper soil layer to socket into a firm bearing stratum of finite stiffness. An extensive parametric study is carried out to investigate the influence of various parameters on the performance of the socketed pile groups. The graphical solutions can be conveniently used to estimate the settlement of the pile groups at normal working loads. Application of the theoretical solutions is illustrated by a case study on the settlements of two multistory buildings supported on socketed pile groups.

In stability problems, the failure probability associated with the critical slip surface is known to be smaller than that for the system that comprises all potential slip surfaces. The difference depends on the correlation between the failure probabilities of the different slip surfaces. Calculations of the upper bound of the probability of system failure were made for the Congress Street cut, in Chicago. The computed upper bound of the probability of system failure is about twice the failure probability for the critical slip surface. The failure probabilities for the slip surfaces that pass through the two clay layers near the bottom of the cut have about the same value. Because of the assumption that the strengths of these layers are statistically independent, the safety factor of a slip surface that passes through the upper clay layer but not the lower one is poorly correlated with that of a slip surface that passes through both layers. This leads to a large difference between the failure probability of the system and that of the critical slip surface.

TO better understand the factors influencing the driveability and bearing capacity of vibro‐driven piles, a large‐scale laboratory study was performed. The testing system consisted of a pressure chamber to simulate in situ stresses, a 4‐in.‐ (102‐mm‐) diameter instrumented displacement pile, a model vibratory driver, and a model impact hammer. The influence of soil and vibro‐driver parameters, in situ stress conditions, and restriking with an impact hammer on the performance of vibro‐driven pile was investigated. The soil parameters of interest were particle size (effective grain size of 0.2 mm and 1.2 mm) and relative density (65% and 90%). The vibratory‐driver parameters of interest were the frequency, eccentric moment, and bias weight applied to the vibrator. Based on maximum rate of penetration of the pile, an optimum driver frequency of 20 Hz was observed for the vibro‐driver‐pile‐soil system under investigation. The optimum driver frequency was not affected by the range of soil conditions, eccentric moment, and bias weight investigated. The relative density of soil has the greatest influence on the rate of penetration of vibro‐driven piles. Static and dynamic unit‐load‐transfer relationships were developed for piles driven by vibration and compared with those obtained for piles driven by impact under similar conditions. Impact‐driven piles developed higher capacity than vibro‐driven piles in medium‐dense sand (65% relative density), but the reverse was observed at 90% relative density, with vibro‐driven piles having greater bearing capacity.

Methods available for estimating the bearing capacity of piles installed with vibratory drivers are inadequate and do not explicitly incorporate important variables, such as soil parameters and in situ stresses. The influence of relative density (65% and 90%), particle size (0.2 mm and 1.2 mm), and in situ horizontal stress (10 psi and 20 psi) on the load‐movement relationship and bearing capacity of vibro‐driven displacement piles in sand is investigated using a large‐scale laboratory testing system. The test results indicate that, among the variables investigated, the most important parameter influencing the rate of penetration and the bearing capacity of the vibro‐driven piles is the initial relative density of sand deposit. Based on pile capacity tests and analytical study, several models are proposed to predict the nonlinear unit load‐transfer curves, load‐movement relationships and bearing capacity of vibro‐driven displacement piles. The model parameters are related to the important test variables investigated in this study. The model predictions are in agreement with the experimental results. Performance of vibro‐driven piles is compared with that of impact‐driven piles.

The hydraulic conductivity of a highly plastic, compacted clay soil is significantly influenced by the size of clods used in preparing the soil for compaction. For soil compacted dry of optimum, hydraulic conductivity is 1,000,000 times smaller when the soil is prepared from small (4.6‐mm) rather than large (19‐mm) clods. For soil compacted wet of optimum, clod size is unimportant. Large differences are seen in the hydraulic conductivity of soils compacted with standard versus modified Proctor procedures. The conclusion reached is that the fate of clods and interclod pores during soil processing and compaction controlled the hydraulic conductivity of the compacted soil. To achieve low hydraulic conductivity, it is necessary to destroy the clods and to eliminate large interclod pores either by wetting the soil to a high water content or using a large compactive effort.

Saprolites derived from a mica schist and a quartz schist from southwestern Nigeria are compacted at three energy levels, namely 0.6 MNm/m³, 1.1 MNm/m³, and 2.7 MNm/m³, and subjected to consolidation and permeability tests. Despite their high mica contents—25% and 30%, respectively—the saprolites attained fairly high maximum dry densities (1.68–2.04 t/m³). For each saprolite, increased compaction energy reduced compressibility appreciably but caused virtually no difference in permeability; the quartz schist saprolite being less compressible and less permeable than the mica schist saprolite. The compressibilities varied from low to very low while the saprolites have very low permeability for all the compaction energies. Comparison of the results of these tests on this mica schist saprolite with those of mica schist saprolites obtained from high horizons shows that the mica schist saprolite used in this study is better suited for use as subbase and fill material.

The commonly used hyperbolic function is known to be deficient in accurately modeling failure even though it is easily fitted to the initial conditions. To correct that deficiency, a modified hyperbolic function which includes a power term is proposed. The modified hyperbolic function is shown to offer more versatility and accuracy in modeling shear stress-strain behavior in both monotonic and cyclic loading conditions; at both low and high strain levels. A plot of the shear stress-strain curves generated using the proposed equation is included and discussed. It is shown that the generated shear stress-strain curves fit the range of values typically adopted for sands and clays. Equivalent viscous dampings for a nonlinear, hysteretic material are computed for the curves generated with the modified hyperbolic equation. A plot of variations of damping ratios with strain level is included to illustrate the versatility of the modified hyperbolic equation in fitting the range of values typically used for sands and clays.