Laboratory Measurements of Void Fraction and Turbulence in the Bore Region of Surf Zone Waves

Laboratory measurements of the instantaneous free surface, horizontal velocity, and void fraction fluctuations were made simultaneously for three cases of regular waves breaking on a plane slope. The data were reduced by ensemble averaging to quantify the temporal variation of the turbulence intensity and void fraction above trough level in the aeration region of the breaking waves. The cross-shore location of the measurements was restricted to the transition region marked by a rapid decrease in wave height. The study showed that the maximum ensemble-averaged void fractions were between 15 and 20% and that the temporal variation of the normalized void fraction above the still water level could be modeled by linear growth followed by exponential decay. The temporal variation of void fraction above the still water normalized by the wave period and average void fraction appears to be self-similar.     

Preferential Flow in a Reclamation Cover: Hydrological and Geochemical Response

Evapotranspirative covers used for waste containment or land reclamation strategies are intended to function in perpetuity. Pedogenesis of the cover materials caused by biophysical processes may lead to the development of macroporosity (i.e., preferential flow paths), which will alter the hydrological response from the intended design function. Hydrometric and geochemical data were used in this study to examine the contribution of preferential flow to the hydrological response of a reclamation cover on saline-sodic shale mine overburden, in a cold semiarid environment. The hydrometric data suggest that infiltration occurs along preferential flow paths when the ground is frozen or when wet antecedent soil moisture conditions develop prior to precipitation events. Interflow is initiated during the spring snowmelt when the cover thaws and water migrates from the preferential flow paths into the soil matrix, causing a perched water table to form on the cover-shale interface. The cessation of interflow coincides with a recession of the perched water table and an increase in matric suction within the cover in response to elevated evapotranspiration demands. The chemistry and stable isotope signature of the interflow demonstrates that these waters are initially composed of fresher snowmelt water, flowing along preferential flow paths, which then transition to pre-event water dominated by higher concentration water from within the soil matrix. A numerical simulation demonstrates that macroporosity imposes a significant control on the discharge rate and cumulative volume of interflow.     

Three-Dimensional Linear and Simplified Nonlinear Soil Response Methods Based on an Input Wave Field

We propose three-dimensional linear and simplified nonlinear soil response methods based on an input seismic wave field. An input wave field is employed to treat seismic surface waves excited by a deep structure in a shallow soil model. First, the linear method is applied to a hard- and a soft-soil site located in Mexico City, and soil responses excited by S-, surface-, and whole-wave fields reproduce the input waves fields well. Then, the linear method is applied to estimate soil responses for three large earthquakes at two soft-soil sites located in the reclaimed zone of Tokyo Bay, and again it works well. Finally, we attempt to perform nonlinear and liquefaction soil response analyses in the reclaimed zone, on the basis of an input wave field modified according to varied soil properties. The nonlinear method seems to provide reasonable nonlinear and liquefaction soil responses.