Engineering Commons^™

Predicting Solute Transport In Natural Streams - A Stochastic Approach, Xueqing Zhou

Dissertations and Theses

The existing theories for predicting longitudinal dispersion in straight open channels have long been recognized as inadequate when applied to natural rivers. These theories tend to grossly underestimate dispersion in real streams since an important mixing mechanism due to nonuniform river cross-section variations is not explicitly taken into account. Recognizing the important role of stream irregularities on solute transport and the analytical difficulties of classical deterministic analysis, we develop a stochastic approach for analyzing solute transport in natural streams. Variations in river width and bed elevation are conveniently represented as one-dimensional random fields, characterized by their autocorrelation functions. Advection and …

Two Dimensional Finite Element Modeling Of Swift Delta Soil Nail Wall By "Abaqus", Richard James Barrows

Dissertations and Theses

Soil nail walls are a form of mechanical earth stabilization for cut situations. They consist of the introduction of passive inclusions (nails) into soil cut lifts. These nailed lifts are then tied together with a structural facing (usually shotcrete) . The wall lifts are constructed incrementally from the top of cut down. Soil nail walls are being recognized as having potential for large cost savings over other alternatives. The increasing need to provide high capacity roadways in restricted rights of way under structures such as bridges will require increasing use of techniques such as combined soil nail and piling walls. …

The Influence Of Hydrodynamics And Particle Size On The Rejection Properties Of Ultrafiltration Membranes, Usama M. Shahin

Theses

A mathematical model based on the flow hydrodynamics is developed to calculate the treatment efficiency of ultrafiltration process. This model relates the treatment efficiency with the consideration of both fixed parameters and variable parameters. The fixed parameters are function of the intrinsic rejection coefficient, diffusion coefficient, and viscosity whereas the variable parameters can be related to the fluid velocity, volume flux, and cartridge dimensions. The model has been examined by solutions with solutes that have different molecular weights. The experimental data fits the proposed mathematical model very closely suggesting its suitability to evaluate the rejection efficiency in ultrafiltration. As such …

Behavior Of Concrete And Slender Reinforced Concrete Columns Under Cyclic Axial Compression With Bidirectional Eccentricities, Byong Youl Bahn

Dissertations

A rational analysis of reinforced concrete (R/C) structures requires satisfactory modeling of the behavior of concrete under general loading patterns. The behavioral characteristics of concrete dominantly depends upon its load history. For the study of concrete behavior, parametric study and experimental investigation into the behavior of concrete under load history of random cycles are performed. Through parametric study, the applicability of the previous concrete models is examined and a physically motivated modeling for the cyclic stress-strain relationships is proposed. The present modeling of concrete under general cyclic loading is initiated to provide substantial applicability, flexibility of mathematical expressions and furthermore …

Theoretical Evaluation Of The Break Off Test For Concrete, Arjuna Priyara Ranasinghe

Dissertations

Strength of concrete is normally measured using the standard cylinder or cube. The measured strength is used for design. The accuracy of concrete strength is frequently challenged, particularly in large concrete structures where size effect of the test specimens is attributed for the differences. Many nondestructive tests were developed to evaluate concrete strengths. In recent years, it was obvious that these tests are unreliable. As the infrastructure decays, more nondestructive tests are required to evaluate the existing structures.

The Break Off Test is a recently developed nondestructive test. Although substantial amount of experimental investigations have been carried out on this …

Behavior Of Biaxially Loaded Concrete-Encased Composite Columns, Pedro Ricardo Munoz

Dissertations

The theory of nonlinear behavior of biaxially loaded short and slender composite columns is used to study the load-deformation and moment-curvature of four pin-ended composite column specimens tested under axial compressive load and biaxial bending moments in a single curvature. The accuracy of the test results is verified by comparison with analytical results obtained by a method of analysis that includes the nonlinear material properties of concrete and steel and covers the ascending and descending branches of the linear segmented column specimen. A computational method is presented to model the analytical behavior of the biaxially loaded composite column. Its validity …

Design, Construction, And Operation Of Water Treatment Plant Residual Monofills, Haitao Bian

Theses

Due to the stringent environmental regulations, landfilling becomes the most viable option for ultimate disposal of water treatment plant (WTP) residues. At present, most states apply the regulations for municipal solid waste (MSW) landfills to the landfilling of WTP residues. This is too stringent since the WTP residues are not hazardous. Therefore, development of suitable criteria for WTP residual monofills is necessary and urgent.

A set of environmental and geotechnical experiments was conducted to characterize WTP residues. It can be concluded that very little leachate will be produced and migration of leachate is unlikely. Also it was noted that insignificant …

Geotechnical Characterization Of Water Treatment Plant Residuals, Zhengyuan Xia

Theses

Evaluation of engineering properties of water treatment plant (WTP) residuals is a critical part in predicting their behaviors in monofills. In this study, ten WTP residual samples were collected from ten water treatment plants across the United States. Their general chemical/physical and geotechnical properties including liquid and plastic limits, compaction) shear strength, permeability and durability characteristics were determined.

It was observed that the geotechnical properties of WTP residuals are influenced by various factors such as mineral particle composition, organic content, type and amount of chemical additives) and time of aging, etc. Based on this study, the behavior of WTP residual …

Landfill Leachate Production And Gas Generation Numerical Model, John Edward Riester Jr.

Civil & Environmental Engineering Theses & Dissertations

Numerous processes occur in landfills which lend themselves to modeling. Many of the processes are mutually interdependent. An unsteady numerical model is developed combining the major processes. The three-dimensional moisture transport equations and boundary conditions are solved using an implicit finite difference scheme. The boundaries are determined through a two-dimensional runoff model for the landfill surface and a one-dimensional leachate liner flow model at the bottom of the landfill. The runoff model accounts for evapotranspiration, runoff, infiltration, and leachate recirculation. Richard's equation is solved for saturated and unsaturated vertical flows and Darcy's Equation is solved for lateral flow between adjacent …