Journal of Geotechnical and Geoenvironmental Engineering

This paper presents an experimental investigation of the concept of effective density for the propagation of small-strain shear waves through saturated granular materials. Bender element tests and resonant column tests were conducted on various granular materials in dry and saturated conditions. Values of small-strain shear modulus for the dry condition are compared with corresponding values for the saturated condition, which are calculated using saturated density and effective density. For bender element tests, the use of saturated density produced errors as high as 28% in the shear modulus, whereas the use of effective density resulted in errors generally less than 5%. For resonant column tests, errors in the shear modulus that were obtained using saturated density were smaller than those for bender element tests because of the lower range of excitation frequency and effect of mass polar moment of inertia of the loading system. A quick chart is provided to help users determine if effective density should be considered for a given application. Effective density is expected to be important for fine and medium sands at high-frequency excitations, such as bender element tests, coarse clean sands at lower frequencies, such as for resonant column tests, and clean gravels at essentially all frequencies of geotechnical interest.

Significant developments have taken place over the past 20 years to evaluate the liquefaction potential of soils using in situ tests. The cone penetration test (CPT) is now commonly used to evaluate liquefaction potential in soils. There have also been significant developments to evaluate liquefaction potential based on in situ shear wave velocity ($V_s$) measurements. Liquefaction methods base on shear wave velocity have the advantage that they are essentially independent of soil characteristics, such as fines content, but often lack the stratigraphic detail obtained using the CPT. Liquefaction methods based on the CPT have the advantage of continuous, repeatable measurements but require corrections based on soil characteristics that can be significant in soils with high fines content. Comparing the most recent $V_s$-based method with a CPT-based method provides an independent evaluation of the associated corrections applied to the CPT-based method. This paper compares the current $V_s$-based method with a specific CPT-based method from the literature to evaluate the associated CPT-based corrections. The paper also examines the advantage of using both CPT and $V_s$ measurements (e.g., using the seismic CPT) to evaluate liquefaction potential.

An empirical model for the estimation of residual strength is proposed. The proposed model predicts residual strength as a nonlinear function of both penetration resistance and initial effective stress. The model is consistent with steady-state concepts and behavior observed in laboratory tests, but was calibrated on the basis of residual strengths back-calculated from flow-side case histories. The back-calculated strengths considered inertial effects, hydroplaning, uncertainties, the conditions under which flow sides are known not to have occurred in past earthquakes, and the relative quality of each case history. The proposed model predicts residual strengths that are generally between those predicted by direct approaches and those predicted by normalized strength approaches. The proposed model also allows estimation of the probability distribution of residual strength.

Dike risk management requires breaching parameters that can be estimated rapidly to support the prediction of inundation zones and decision making. The objectives of this paper are to compile a database of dike breaching cases, study common dike failure mechanisms, and develop a set of empirical equations for estimating breaching length, depth, and peak discharge. A database of over 1,000 dike failure cases was collected, with information on pre-breach dike geometry, materials, type of dike, failure mechanisms, breaching length, depth, and peak discharge. A set of regression models are formulated using five control variables: dike height, width, material, type of dike, and failure mechanism. The standard error is set as a selection criterion and the Akaike information criterion is used to optimize the proposed empirical models. The new models are validated using independent cases and compared with available empirical equations for dikes and man-made dams.

The effects of consolidation under a footing are generally viewed as beneficial due to the resulting increased capacity. Consolidation may also be actively sought because it minimizes footing embedment, which can be critical for the installation of mobile offshore jack-ups because available leg length is limited. However, it can also set the platform footing up to subsequently punch through the strengthened zone, with potentially serious consequences. The problem is complex due to the three-dimensional nature of consolidation. Further, footing penetration leaves the soil above heavily remolded and generates large excess pore pressures below, such that the soil state even prior to consolidation is significantly altered from its in situ conditions. This study has taken an experimental approach to investigate the effects of consolidation around a footing penetrating into carbonate silty clay and, following detailed discussion of the response, offers a framework to predict the changes to the load-penetration curve.

This technical note describes a method aimed at correcting the dilution effect of the apparatus on the solute transport parameters determined by column testing. The method requires quantification of the dead volume (i.e., not drainable during sample collection) of the permeation apparatus and makes use of a closed-form solution to the advection-dispersion-reaction equation (ADRE) equation used to infer transport parameters from column test results. Simulations of the dilution effect were performed and actual experimental data were analyzed, with reference to testing equipment frequently used in column studies (flexible-wall permeameter and bladder accumulators) and to porous materials commonly used in pollutant containment [geosynthetic clay liners (GCLs) and compacted clay liners (CCLs)]. Results showed that the dilution effect of the testing apparatus can significantly affect the determined transport parameters, in particular by increasing the retardation factor and reducing the diffusion coefficient.