Many highly urbanized cities are faced with the problem of disposal of municipal solid waste because of the scarcity of land available for landfilling. One possible solution is the incineration of the municipal solid waste. After incineration, about 20% by weight of fly ash and other residues are produced. Investigations into the physical and engineering properties of the fly ash derived from municipal solid‐waste incineration indicate that the material is a potential source of fill material, with low compacted density and high strength. The fly ash was relatively free draining, with permeability of the same order of magnitude as coarse grained materials. The use of the fly ash as an admixture in the stabilization of a soft marine clay showed improved undrained shear strengths and lower compressive properties. Leachate tests on the samples of fly ash initially indicated trace quantities of cadmium and chromium in excess of the acceptable drinking‐water limits. After leaching for 28 days, the concentrations fell below the drinking‐water limits. Lime and cement can be used to stabilize the fly ash. The concentrations of heavy metals in the leachates of lime and cement treated fly ash were nondetectable.

Soils showing changes in plasticity characteristics upon drying form an important group in tropical soils. These changes are attributed to the grouping of particles into aggregates either due to mineralogy or presence of cementing agents and/or pore fluid characteristics. These changes are found to be permanent. In this paper, the effect of these changes leading to changes in index properties is discussed. The coefficient of permeability has been found to be comparable at liquid limit water content for different soils of varying liquid limit values. Permeability is an indirect reflection of microstructure and indicates the flow rate, which depends upon pore geometry. Other mechanical properties like compressibility and shear strength also depend upon pore geometry. These microstructural aspects of liquid limit as a reference state for the analysis of engineering behavior of tropical soils are examined in detail.

The general impression with tropical soils showing changes in plasticity characteristics upon drying is that the compressibility decreases, and shear strength and permeability increase with drying. The study reported in this paper within the frame work of generalized state parameter approach shows that these observations, in a general sense, need be treated with caution. Drying causes a reduction in the overall potential represented by liquid limit leading to a reduction in void ratio for equilibrium under a given load such that the same pore structure exists when equilibrium condition is reached. This means the permeability coefficients do not increase with drying under a given load but considerable settlement occurs. Further, due to the reduction in void ratio, under a given external loading, being commensurate with the reduction in liquid limit due to drying, shear strength also does not increase with drying.

An evaluation of water sources and extent of wetting at a collapsible soil site is presented. The field and laboratory data were collected after distress of an existing structure was observed. The underlying soils at the site were highly variable in fines content, density, and degree of saturation. Because of the high variability of soil properties, suction contours were developed for the site to evaluate the extent of soil wetting. A relationship between soil suction and basic soil parameters was developed for use in constructing these contours. The depth of wetting obtained using the suction contours was consistent with other data at the site, including quantity of water introduced and standard penetration test results. Laboratory collapse curves were used to estimate the settlement at the site for the depth of wetting inferred from the suction contours. The computed settlements, taking into consideration partial wetting effect, were consistent with observed settlements of the structure.

Recent experimental studies revealed that when the drainage condition of loose sand is switched from drained to undrained it can manifest runaway instability prior to attaining the failure stress state. To study this type of unstable behavior (referred to as prefailure instability) under more‐general conditions, the strain‐path testing technique was used to constrain the strain development of a triaxial sample along a constant strain‐increment‐ratio path. Medium‐loose to dense samples were used in this study. Provided certain conditions are met, prefailure instability can occur even for a dense sample. The factors affecting the occurrence of instability are established from test results. Two instability conditions are established for predicting of instability under a general stress‐controlled condition. These two conditions require input parameters that are relatively simple to obtain yet can accurately predict the occurrence of instability. For the special case of undrained condition, these two instability conditions degenerate to those proposed by previous researchers.

The dynamic response of vertically excited rigid foundations on an elasto‐viscoplastic half‐space is investigated in the context of nonlinear finite element (FE) analysis. A deviatoric viscoplastic theory with a linear combination of isotropic and kinematic hardening is used to model the soil constitutive response. Large‐scale nonlinear FE computations are made feasible by the use of a composite Newton‐preconditioned conjugate gradient (PCG) iteration technique, which requires the factorization of the consistent tangent operator no more than once during the solution process. Time‐domain analyses are used to investigate the nonlinear responses of vertically oscillating circular and square foundations to harmonic loads, using two‐ and three‐dimensional FE modeling, respectively. For low‐frequency excitations, resonance is created, which amplifies the motion of the foundation at amplitudes well above those obtained at the zero‐frequency level. This behavior is in stark contrast to the linear elastic response of vertically oscillating finite‐size foundations on a homogeneous half‐space, in which the amplitude of the motion is known to decrease monotonically with increasing values of the excitation frequency. The resonance phenomenon is explained in the context of a single‐degree‐of‐freedom oscillator analog that has been used successfully by previous investigators to model prototype continuum soil‐structure interaction problems.

Flexible walls and struts in braced excavations are designed to provide lateral support and to ensure that wall movements during the excavation are not excessive. Lateral pressures and wall movements are influenced not only by soil conditions, but also by other important factors such as drainage conditions and soil‐structure interaction. We use finite element modeling to investigate the impact of these factors on typical strutted wall system response, focusing on the magnitude and distribution of lateral pressures and the pattern of lateral wall deflections. For permeable soils, an important factor that affects the wall system response, is movement of fluids since it not only changes the magnitude and distribution of lateral pressures behind the wall but may also induce excessive ground subsidence resulting from vertical consolidation. Lateral wall deflections also may be greater for a smooth wall due to the loss of tangential interaction between the wall and the soil backfill. Finally, a case study on excavation through layers of saturated dense sands is presented to demonstrate the utility of the numerical model in situations where some provision for drainage is clearly appropriate.

Data are presented from cyclic triaxial tests on anisotropically consolidated kaolin clay and silica silt mixtures prepared in the laboratory. The soil type ranged from a pure silt to a silty clay with 40% clay content. The undrained behavior of clay‐silt soils subjected to anisotropic cyclic loads without shear stress reversal can be adequately described by the average resultant cyclic strain rate provided that the test conditions account for strain rate effects and cross‐sectional area changes during straining. Strain rate effects in cyclic triaxial tests may induce nonuniform pore pressure distribution within the specimen. Nonuniform pore pressure effects are related to the average resultant cyclic strain rate, while the dynamic strength parameters are related to the maximum cyclic strain rate. It has been established that the average resultant cyclic strain rate depends upon the imposed static shear stress, the cyclic stress ratio and clay content. Cyclic frequency, however, did not significantly affect the 20% clay/80% silt mixtures.

The rectangular hyperbola method ($T_v/U$ versus $T_v$) is extended to the case of drains and surcharge by considering the hyperbolic plots for combined vertical and radial flow consolidation in clays of varying thickness and drain spacing ratio for typical soil properties of $c_v$ of 1–5 m²/yr. The results indicate that the hyperbolic plots are linear between $U_{50\%}$ and $U_{90\%}$. For the lines radiating from the origin to $U_{50\%}$ point, the slope is $(1/0.5=2.0)$, and to the $U_{90\%}$ point, the slope is $(1/0.9=1.11)$. Thus, the ratio of the slopes of these radiating lines to the slope of the linear portion of the hyperbolic plots identifies the $U_{50\%}$ and $U_{90\%}$ for any settlement record using drains and surcharge. It is found that the estimate of ultimate settlement from the $U_{50\%}$ and $U_{90\%}$ is more accurate than the conventional inverse slope approach of the hyperbolic method, especially for data between the 50% and 90% consolidation points. This finding is demonstrated by applying it to a well‐documented case history of the long‐term full‐scale loading tests at Skå‐Edeby, Sweden.

Field quality control on an earthdam consists of three complementary and somewhat overlapping operations: visual inspection and continual corrections of the works in progress, gauging the process and the product, and monitoring the dam by instrumentation. The present work concentrates on the second operation, gauging, which is based principally on sampling, with subsequent testing and recording numerous data. Modern statistical graphics offers most powerful tools in extracting and succinctly conveying essential information from a multiplicity of recorded data. In our case this information is essential in two respects: (1) During construction, in pointing at the rate of occurrence and the severity of quality defects, so as to take timely remedial actions; and (2) after completion of the project, in: (1) Assessing the overall performance of the gauging operation; and (2) providing a conspectus of the properties in the accepted product.

Placing a conical‐shaped mound of soil on the ground surface provides a method for performing a large‐scale test load for characterizing the in situ compressibility of ground. This paper describes the test and gives an example of its use to measure the compressibility of a dynamically compacted construction debris fill, including delayed compression effects. It also includes an extension of consolidation theory to under the axis of a conical loading.