Physical Modeling of Flow Nets in Groundwater and Determination of Hydraulic Conductivity

The goal of this study is to physically model the paths that water particles take through soil, and estimate hydraulic conductivity for several soil configurations. Water paths, or flow lines, are shown by injecting dye into sand contained in a rectangular acrylic glass tank with a vertical barrier in the center; water is poured on one side of the tank and a pump is used to maintain constant head loss. If flow lines are formed, a flow net is to be drawn using photos of the tank and hydraulic conductivity is to be calculated. This project consists of four phases: design, construction, testing, and analysis. At the time of this report, the design phase is complete and the construction phase is active. Upon completion of the construction phase, testing will begin using four configurations of sand. Sand variables include coarse or fine sand types, and loose or dense sand placement in the tank. Tests consist of injecting potassium permanganate, referred to mainly as “dye” in this study, into the sand surface in two parallel lines running laterally across the tank. Water is then poured on one side of the acrylic glass barrier, and water outflow on the opposite side of the tank is measured. During the analysis phase, which follows directly after testing, hydraulic conductivity is calculated as described in the Methodology section. If possible, a flow net will be drawn as described in the Background Information and Methodology sections. Hydraulic conductivity calculations will be compared to theoretical values for different types of sand and percent differences are calculated. Discrepancies in hydraulic conductivity will demonstrate how closely experimental sand resembles ideal coarse and fine sand. If a flow net is drawn, the applicability of Darcy’s law will be explored and discussed

Climate Change and Eutrophication: A Short Review

Water resources are vital not only for human beings but essentially all ecosystems. Human health is at risk if clean drinking water becomes contaminated. Water is also essential for agriculture, manufacturing, energy production and other diverse uses. Therefore, a changing climate and its potential effects put more pressure on water resources. Climate change may cause increased water demand as a result of rising temperatures and evaporation while decreasing water availability. On the other hand, extreme events as a result of climate change can increase surface runoff and flooding, deteriorating water quality as well. One effect is water eutrophication, which occurs when high concentrations of nutrients, such as nitrogen and phosphorus, are present in the water. Nutrients come from different sources including agriculture, wastewater, stormwater, and fossil fuel combustion. Algal blooms can cause many problems, such as deoxygenation and water toxicity, ultimately disrupting normal ecosystem functioning. In this paper, we investigate the potential impacts of climatic factors affecting water eutrophication, how these factors are projected to change in the future, and what their projected potential impacts will be

Toughness, Tenacity and Maximum Initial Strength of Rubber Modified Asphalt Binders

The toughness and tenacity test method, which was developed in the 1980s, is popular for evaluating a polymermodified binder. Several states like Nevada require performing this test to evaluate non-modified binder samples, as well as other types of modified binders. In this regard, a toughness and tenacity test was performed on rubber-modified samples produced from virgin binder PG58-28, PG64-16 and AC-20. In order to take the rubber size, type and content into account, two rubber sizes, mesh #20 and #40, two rubber types, ambient and cryogenic, and three rubber contents, 10%, 15%, and 20% were produced and tested. The results then were compared with polymer-modified and terminally blended rubber-modified samples. The results show improvement in the amount of initial maximum strength, and a decline in the magnitude of elongation, toughness and tenacity for the rubber-modified binder, compared to other types of binders

Flow-Induced Stresses and Displacements in Jointed Concrete Pipes Installed by Pipe Jacking Method

Transient flows result in unbalanced forces and high pressure in pipelines. Under these conditions, the combined effects of flow-induced forces along with sudden pipe displacements can create cracks in the pipeline, especially at the junctions. This situation consequently results in water leakage and reduced operational efficiency of the pipeline. In this study, displacements and stresses in a buried pressurized water transmission pipe installed by pipe jacking method are investigated using numerical modeling and considering interactions between fluid, pipe, and soil. The analyses were performed consecutively under no-flow, steady flow, and transient flow conditions, in order to investigate the effects of flow conditions on displacements and stresses in the system. Analyses of the results show that displacements and stresses in the jointed concrete pipes are significant under transient flow conditions. Moreover, because of pressure transient effects, maximum tensile stresses exceed the tensile strength of concrete at the junctions, leading to cracks and consequent water leakage

Effect of Inlet Angle from Tributary into Main Channel

Open channel flows play a significant role within major metropolitan areas in the removal of excess surface runoff. Main channels are responsible for the removal of all excess surface runoff which are fed by connecting tributaries. Both main channels and tributaries can occur naturally or be manmade but their orientation must be considered in the removal of excess surface run off. It is believed that the angle in which the tributaries connect to the main channel is an important factor in whether the run off is removed efficiently or a major contributor to flooding. Current practice requires tributaries in flood control channels to enter at small angles to avoid disrupting flow in the main channel and impacting channel capacity. These small angles are costly to construct and their value is questionable, especially when tributary flow is small compared to the main channel capacity. This is often the case, especially for smaller tributaries and conduits. There is a need to evaluate the impact of tributary discharges into open channels across a range of flow rates, velocities, and entrance angles

Identification of Critical Source Areas (CSAs) and Evaluation of Best Management Practices (BMPs) in Controlling Eutrophication in the Dez River Basin

Best Management Practices (BMPs) are commonly used to control pollution in the river basins. Prioritization of BMPs helps improve the efficiency and effectiveness of pollution reduction, especially in Critical Source Areas (CSAs) that produce the highest pollution loads. Recently, the Dez River in Khuzestan, Iran, has become highly eutrophic from the overuse of fertilizers and pesticides. In this basin, dry and irrigated farming produce 77.34% and 6.3% of the Total Nitrogen (TN) load, and 83.56% and 4.3% of the Total Phosphorus (TP) load, respectively. In addition, residential, pasture, and forest land uses together account for 16.36% of the TN and 12.14% of the TP load in this area. The Soil and Water Assessment Tool (SWAT) was implemented to model the Dez River basin and evaluate the applicability of several BMPs, including point source elimination, filter strips, livestock grazing, and river channel management, in reducing the entry of pollution loads to the river. Sensitivity analysis and calibration/validation of the model was performed using the SUFI-2 algorithm in the SWAT Calibration Uncertainties Program (SWAT-CUP). The CSAs were identified using individual (sediment, TN, TP) and combined indices, based on the amount of pollution produced. Among the BMPs implemented, the 10 m filter strip was most effective in reducing TN load (42.61%), and TP load (39.57%)

Influence of lithophysae geometry on mechanical properties of Hydro-Stone®

85 percent of YM drift tunnels will be constructed in lithophysal volcanic tuff. Rock behavior depends on porosity. Limited experimental data exists to characterize rock porosity and dependencies on properties such as σc , E, and n

Literature Review: Biocement for Stabilization of Expansive Soils in Las Vegas, Nevada

The aim of this study was to present a possibility for the use of biocementon expansive clay. Expansive soil is a type of clay when exposed to water and moisture changes its volume. Due to the clays swelling and shrinkage behavior itsdifficult to use it in engineering and construction projects, therefore costly and unhealthy techniques have been used to stabiliseexpansive soil in order to address the problem [12]. A possible healthy and environmentally friendly solution is Biocement which uses microbial induced calcite precipitation (MICP) in order to help aggregate soil to form a stable cementitiousmaterial. MICP isdependent on the innate process of urea production in Microorganisms that utilizes the production of urea to form carbonate through the process of hydrolysis speed up by the urease enzyme [3]. The use of biocementationis being applied to many fields such as construction and erosion control [9]. However, there are many other processes that can utilize this technology for its benefit. In this review, we used a systematic method and set parameters to find literatures where we could analyze if biocementwould work onexpansive clay and ifwe could narrow to an organism that would work best for future experiment. We ended up with 13 publicationwhich we summarized in table 1. We looked at the publications the type of organisms they used, the type of soil they, permeability, porosity, strength, optimal temperature, optimal pH, and cell concentration. We concluded that biocementation could be used with expansive clay and that it would be able to improve its permeability to water and improve its strength. We also concluded that Sporosarcina pasteurii was the optimal organism to use. However, there was limited publication on thetopic therefore further studies need to be conducted

Effect of Fiber Reinforced Polymer Tubes Filled with Recycled Materials and Concrete on Structural Capacity of Pile Foundations

This paper deals with analyzing the structural responses of glass-fiber-reinforced polymer (GFRP) tubes filled with recycled and concrete material for developing composite piles, as an alternative to traditional steel reinforced piles in bridge foundations. The full-scale GFRP composite piles included three structural layers, using a fiber-oriented material that was inclined longitudinally. Almost 60% of the fibers were orientated at 35° from the longitudinal direction of the pile and the rest 40 percent were oriented at 86° from the horizontal axis. The segment between the inner and outer layers was inclined 3° from the hoop direction in the tube. The behavior of the filled GFRP tubes was semi-linear and resulted in increasing the total ductility and strength of the piles. Adjusting the material’s properties, such as the EAxial, EHoop, and Poisson ratios, optimized the results. The lateral strength of the GFRP composite pile and pre-stressed piles are investigated under both axial compression and bending moment loads. Based on the conducted parametric study, the required axial and bending capacities of piles in different ranges of eccentricities can be reached using the combination of tube wall thickness and GFRP fiber percentages

Influence of lithophysal geometry on the uniaxial compression of tuff-like rock

The purpose of this report is to summarize the work and present conclusions of Project Activity Task ORD-FY04-013 conducted under Cooperative Agreement No. DEFC28- 04RW12232 between the U.S. Department of Energy and the Nevada System of Higher Education (NSHE). This document describes results of laboratory testing on analog lithophysal tuff (Hydro-StoneTB®) conducted in the Department of Civil and Environmental Engineering of the University of Nevada at Las Vegas (UNLV) from 2004 to 2006