River-Ice Ecology.?II: Biological Aspects

River ice is an integral and important component of the flow regime in cold-regions environments. As demonstrated in a companion paper, it can significantly affect many of the hydrologic, geomorphic, and chemical characteristics of a river. Building on such a physical template, this paper reviews the related biological effects at all stages of winter ice cover, including the period of autumn cooling, initial freeze-up, main winter, and breakup. Special focus is placed on the role of ice in seasonal movements and avoidance behavior of fish and benthic organisms, the creation of unique in-channel and riparian habitats, the modification of aquatic and floodplain vegetation, and some river-ecology theories, including disturbance ecology and flood-pulse theory. Included is a comprehensive reference list, the most complete ever assembled on this subject.     

PAC-Membrane Filtration Process.?II: Model Application

The models developed in the first part of this study are applied to predict the removal of 4-nitrophenol by powdered activated carbon (PAC) in a bench-scale reactor. A series of continuous-flow filtration experiments were conducted with different carbon doses to verify the modeling approach when the activated carbon was added directly to the membrane reactor, either as step or pulse input, and when the carbon was dosed as a step input to a continuous-flow stirred tank reactor followed by the membrane reactor. The models predicted well the experimental data for all cases investigated. The verified model was used to investigate the effect of various operating parameters on the efficiency of the adsorption process. This analysis included the effect of filtration time, membrane reactor volume, dosing procedure, and the effect of dosing the carbon in reactors installed in series upstream of the membrane reactor.     

Border Irrigation Field Experiment.?II: Salt Transport

This paper presents results from an experiment to measure the salt transport processes within a border-irrigated bay in northern Victoria, Australia, an area with shallow saline ground water and cracking soils. The overland flow and drainage salinity measurements showed that lateral surface washoff of salt from the soil surface was the main process of salt transport into surface water. Soil salinity measurements showed that, although salt was removed from the near-surface soil, there was negligible leaching downward through the profile. This was due to the near saturation of the soil, the presence of cracks that minimize the vertical leaching, as well as the lack of deep drainage of ground water. These findings highlight the importance of lateral washoff in the transfer of salt from irrigation bays, suggesting that reduction in irrigation event volumes is likely to reduce salt export and thus affect the sustainability of irrigation in this area.     

Simplified Spreadsheet Solutions.?II: Overall Schedule Optimization

Overall schedule optimization, considering time, cost, and resource constraints is a difficult task due to the inherent complexity of projects, the difficulties associated with modeling all aspects combined, and the inability of traditional optimization tools to solve this large-size problem. In this paper, a practical approach is presented for the modeling and optimization of overall construction schedules. To simplify modeling, a spreadsheet-based model is developed to be easily usable by practitioners. The spreadsheet model integrates critical-path network scheduling with time-cost trade-off analysis, resource allocation, resource leveling, and cash flow management. The model uses the total project cost as the objective function to be minimized. To facilitate this large-size optimization, a nontraditional optimization technique, genetic algorithms, is used to locate the globally optimal solution, considering all aspects simultaneously. Details of the proposed model are described, and a hypothetical case study was used to experiment with it. Integration of the model with a simple information system is described to automate the development of optimal construction schedules.     

Active Flood Hazard Mitigation.?II: Omnidirectional Wave Control

Active mitigation of unimodal flood waves is achieved by selective boundary flow withdrawal. This is shown to create omnidirectional depression waves that can reduce the impact of hazardous flood waves in wide rivers, harbors, and reservoirs. Boundary outflow is induced by a deliberate levee breach or through an emergency side channel spillway generating disturbances that reflect on the banks of the channel further complicating the wave pattern. An adjoint sensitivity method based on the 2D shallow-water equations is presented to aid in the mitigation of an extreme flooding event by identifying optimal locations and times for the selective withdrawal of flood waters. The efficiency of the method allows adaptive flood control to proceed in real time. It is shown that wave reflections from solid boundaries create a complex pattern of sensitivity waves and multiple options for control. The adjoint sensitivity results become less accurate as the magnitude and duration of the perturbation become large. However, the adjoint sensitivities provide reliable information for identifying optimal locations and times for a selective withdrawal of large magnitude and a fair indication of the spatial dependence of the objective function sensitivity to large changes in flow.     

Modeling Mamala Bay Outfall Plumes.?II: Far Field

The far-field behavior and water quality impacts of the Sand Island, Hawaii, ocean outfall plume were predicted using two models, a statistical short-term model and a long-term model. The short-term model is coupled to a near-field model and uses measurements obtained from Acoustic Doppler Current Profilers. It predicted that the variable currents would cause the visitation frequency of the plume to decrease rapidly with distance. The long-term model predicted that flushing, horizontal diffusion, and decay would result in high dilutions with no significant buildup of contaminants. The frequencies of exceedence of various coliform densities were predicted to decrease rapidly with distance so that bacterial water quality standards should be satisfied very close to the diffuser. Any outfall impacts on the beaches should be very small, and other nonsewage sources are likely to contribute higher levels of bacteria. The effects of treatment upgrades on shoreline water quality will therefore probably be negligible. The results indicate that worst-case conditions are extremely improbable, and their use could lead to overly conservative outfall designs and treatment levels.     

Municipal Solid Waste Slope Failure.?II: Stability Analyses

Analyses are presented to investigate the case of a large slope failure in a municipal solid waste (MSW) landfill that developed through the underlying native soil. The engineering properties of the waste and native soil are described in a companion paper by Eid et al. (2000). Some of the conclusions from this case history include (1) native colluvial∕residual soils in the Cincinnati area underlying MSW can mobilize a drained shear strength less than the fully softened value without recent evidence of previous sliding; (2) strain incompatibility and progressive failure can occur between MSW and underlying materials and cause a reduction in the mobilized shear strength; (3) a stability evaluation of interim slopes, especially when the slope toe will be excavated, blasting will be occurring, and waste placement continues at the top of slope, should be conducted, even though it may not be required by regulations; and (4) the reappearance of cracking at the top of an MSW landfill slope is probably an indication of slope instability and not settlement.     

Adaptive FE Analysis of RC Shells.?II: Applications

This paper deals with the application of an adaptive calculation scheme to ultimate load analyses of reinforced concrete (RC) plates and shells. The influence of the user-prescribed accuracy on the numerical results, especially on the ultimate load, is investigated. Three examples are considered: (1) a shear wall panel; (2) a circular plate; and (3) an RC cooling tower subjected to dead load and wind load. In addition to adaptive finite element (FE) analyses, single-mesh calculations on the basis of uniformly refined meshes are performed.     

Optimal Furrow Design.?II: Explicit Calculation of Design Variables

The furrow irrigation system design problem (at minimum cost) is significantly simplified by analytically solving it. For a specified furrow length, a simple algebraic equation is derived to directly calculate the appropriate inflow rate (and cutoff time) so that the minimum cost of the furrow system is obtained. The proposed equation is independent of the water and labor cost coefficients. Comparison tests indicated that the optimum inflow rate values obtained analytically were in close agreement to the optimum values obtained using the outcome of the zero-inertia numerical model. The method is extended for furrow design considering the furrow length also as a design variable. The optimum number of distribution lines and widthwise furrow sets are easily determined by a simple calculation procedure.     

Water Migration Phenomenon Model in Cracked Concrete.?II: Calibration

The material parameters to express the degree of discontinuity of hydraulic gradient in the developed model (Part I) are calibrated based on the sensible analysis of the experimental results, and then the applicability of the calibrated parameters is discussed. As a result, the material parameters are calibrated by the sensible analysis, and then its relevance can be confirmed by another experiment. Moreover, it can be seen that the normalized permeability of concrete as a nonhomogeneous material by the initial permeability (homogeneous material) can be regressed with three straight lines in the crack width axis with the logarithm. Then the intersection point at the crack width axis shows the critical width at which leakage will not occur. The intersection point at the last two straight lines shows the critical Reynolds number at which flow becomes laminar to turbulent according to the experimental result.     

The “Chunnel” Fire.?II: Analysis of Concrete Damage

In Part I of this study, a material model for the in-situ behavior of rapidly heated concrete was developed that accounts explicitly for the dehydration of concrete and its cross-effects with deformation (chemomechanical couplings) and temperature (chemothermal couplings). In this part of the study, the model is used in finite-element analysis of the tunnel rings of the Channel Tunnel (the “Chunnel”) exposed to fire. An analysis of the finite-element results—i.e., the profiles of temperature, dehydration, stresses, and plastic strains—clearly shows that the thermal spalling that occured during the Chunnel fire is initiated by an in-plane biaxial compressive stress clog closed to the heated surface. The compressive stresses are caused by restrained thermal dilatation and are bounded by chemoplastic softening due to dehydration. They provoke permanent radial deformation, which can be attributed to spalling. The role of thermal damage and thermal decohesion is discussed by comparing elastic, chemoelastic, and chemoplastic stress developments during the 10 h fire exposure. It is found that the salient feature to capture the initiation of thermal spalling at a structural level is the chemoplastic softening behavior at a constitutive material level. It is also shown that a reinforcement on the cold-side, as well as steel fiber reinforcement of concrete, in tunnel rings may significantly increase the risk of thermal spalling.     

Flutter and Buffeting Analysis.?II: Luling and Deer Isle Bridges

The practical applications of the finite-element software developed in Part I of this paper are demonstrated by analyzing the aerodynamic response of two prototype bridges, the Luling Bridge with a streamlined section, and the Deer Isle Bridge with a bluff section. In the Luling Bridge analysis, the self-excited forces are treated as random quantities and the wind turbulence effect is simulated with random parametric excitation analysis. In the Deer Isle Bridge flutter analysis, the self-excited forces are treated as deterministic quantities and the wind turbulence effect is included in the flutter derivatives measured in turbulent wind.     

Performance Analysis for Disposal of Mixed Low-Level Waste.?II: Results

Ten sites were evaluated as potential locations for disposal of mixed low-level radioactive waste using a simple methodology. Three environmental pathways (water, atmospheric, and inadvertent intruder) were analyzed using generic transport models that were modified for site-specific conditions. The results were summarized by grouping the 58 evaluated radionuclides according to their half-lives and environmental mobility and by their limiting pathway (i.e., the pathway providing the lowest permissible radionuclide concentration in disposed waste of the three evaluated pathways). The results indicate that all evaluated sites have the technical capability for disposal of some radionuclides in the waste. For most radionuclides, the intruder scenarios were more important in determining permissible radionuclide concentrations than the other pathways, particularly for arid sites. For humid sites, if the water pathway is not the most limiting and the permissible radionuclide concentration is high, a more sophisticated and rigorous analysis of the water pathway may not be warranted. However, if the permissible concentration is relatively low, more refined analyses may produce higher permissible concentrations based on additional site characterization data.     

Hydrodynamics of Turbid Underflows.?II: Aggradation, Avulsion, and Channelization

A two-dimensional, depth-averaged finite-volume model is used to study the hydrodynamics of turbid underflows. A sensitivity analysis is performed with regard to model input parameters and the initial bed properties. Simulations are then performed to illustrate aggradation and avulsion in an existing submarine channel. The conditions under which channelization of deposits occur are also examined. The effect of numerical dissipation on flow ignition is examined and the high resolution properties of the model are found to produce satisfactory results. The model is applied to historical field-scale events, including the Reserve Fan in Lake Superior and Rupert Inlet in British Columbia.     

Seismic Analysis of Segmental Retaining Walls.?II: Effects of Facing Details

This paper describes a finite-element analysis of two 6-m-high segmental walls, subjected to seismic loading, with special attention to connection performance and permanent deformation of the facing. The first segmental wall uses concrete facing blocks with pins, and the second wall uses the same concrete blocks but without pins. The analysis provides some insight into the behavior of segmental walls, particularly the load transfer mechanism between the geosynthetic reinforcement and the segmental facing units duiring earthquake loading.     

Experiments on Downstream Fining of Gravel.?II: Wide and Sandy Runs

This is the second of two papers about experiments on downstream fining of gravel. Here we briefly summarize the complete series of runs described in the first paper, where the influence of sediment feed rate was evaluated in a narrow channel. We then present results for variation in two more conditions: sand content and channel width. The experiments were carried out in a long flume with an effective 40-m-long test section, with two different widths of 0.3 and 2.7 m. In addition, two sediment mixtures were used with different sand contents (i.e., 33 and 55%) with the remainder being gravel. The following results were obtained. The increase in channel width allowed the formation of transverse topography, enhanced the development of sediment patches, and increased the fining rate of gravel for D50 and finer percentiles. Increasing sand content rendered the long profile of the bed much more concave, caused marked patch development, and most notably increased the fining rate for all percentiles of gravel-sized bed material.     

Probabilistic Nonlocal Theory for Quasibrittle Fracture Initiation and Size Effect.?II: Application

The nonlocal probabilistic theory developed in Part I is applied in numerical studies of plain concrete beams and is compared to the existing test data on the modulus of rupture. For normal size test beams, the deterministic theory is found to dominate and give adequate predictions for the mean. But the present probabilistic theory can further provide the standard deviation and the entire probability distribution (calculated via Latin hypercube sampling). For very large beam sizes, the statistical size effect dominates and the mean prediction approaches asymptotically the classical Weibull size effect. This is contrary to structures failing only after the formation of a large crack, for which the classical Weibull size effect is asymptotically approached for very small structure sizes. Comparison to the existing test data on the modulus of rupture demonstrates good agreement with both the measured means and the scatter breadth.