Sai Kakuturu

Effect of Rejuvenation Methods on the Infiltration Rates of Pervious Concrete Pavements

Pervious concrete pavements in low-traffic urban areas such as parking lots reduce storm water runoff and also minimize water pollution. However, there are concerns about their expected clogging and consequential reduction of hydraulic performance in the long run. The pervious concrete pavements can be declogged using rejuvenation methods such as vacuum sweeping, or pressure washing, or a combination of both. This paper presents the results of our study that focused on the hydraulic performance of pervious concrete pavements. The study included field and laboratory investigations to evaluate the infiltration capacities of the pervious concrete cores and the underlying soils and the usefulness of rejuvenation methods in restoring their hydraulic performance. As a result of this research program, a new field test device, called the embedded ring infiltrometer, was developed for evaluating the infiltration rates of newly installed pervious concrete pavements. The results of this study indicate that the rejuvenation methods can substantially restore the performance of pervious concrete pavements for better management of storm water.

Self-Healing of Concentrated Leaks at Core-Filter Interfaces in Earth Dams

Concentrated leaks at core-filter interfaces in earth dams increase erodibility of soils, which may lead to catastrophic failures. In this paper, mathematical and experimental testing methods are suggested to determine the self-healing nature of these leaks. The methods are fundamentally different from the existing empirical methods in that they do not involve comparison of particle sizes of the base (D85) and filter (D15) soils. They are based on the fundamental processes of particle transport and deposition phenomena. An advection type equation is used with a deposition coefficient (λ) to describe particle transport in filters. The nature of particle deposition at the interface, which is described by an exponential attenuation function with respect to distance, is used to infer the possibility of self-healing. The experimental method involves extension of a test previously published in this journal. The method essentially involves a flow pump to evaluate the erodibility of base soils, determine λ and characterize the filters, and test combined base soil-filter systems to evaluate self-healing potential of a number of filters relative to each other. The results from the experimental method using three different filters and a Group II base soil were interpreted and analyzed using the mathematical model. The methods suggest that the entire particle-size distribution, and not mere D15, governs particle accumulation at the interface. The proposed methods are useful for relative comparison of self-healing capabilities of various filters for a given base soil.

Runoff Curve Numbers for Simulated Highway Slopes under Different Slope, Soil-Turf, and Rainfall Conditions

AbstractHighway infrastructure is a major non-point source of storm water runoff and associated pollutants. Forty-four simulated rainfall tests were conducted over a turf-covered plot-scale test bed that represented typical highway slopes of 25, 33, and 50%. The two soil-turf combinations were Argentine Bahia over AASHTO A-3 soil (fine sand) and Pensacola Bahia over AASHTO A-2-4 soil (silty fine sand). All the tests were conducted in central Florida, where the weather is subtropical. This paper presents the analysis of curve numbers (CN) obtained from simulated rainfall-runoff data. The CN values for the 24 tests conducted on the Argentine Bahia A-3 soil combination varied from 70.4 to 93.0 with a mean value of 79.6. The CN values for the 20 tests conducted on the Pensacola Bahia A-2-4 soil combination varied from 89.0 to 97.2 with a mean of 94.0. The scatter of the CN values was more for fine sand (standard deviation of 8.31) than for silty fine sand (standard deviation of 2.48). Single factor ANOVA sugg...

Total Nitrogen Losses from Fertilized Turfs on Simulated Highway Slopes in Florida

AbstractFertilized highway slopes constitute nonpoint sources of nitrogenous nutrients that are degrading the surface water and groundwater resources. This paper presents the results of simulated rainfall experiments conducted on a plot-scale test bed (slope-adjustable) that was fully exposed to weather for closely representing the conditions of a fertilized turf-covered highway slope in Florida. Thirty-six tests were conducted on three slopes (25, 33, and 50%), simulating two rainfall intensities (12.5 and 25  mm/h). The soils used were fine sand (AASHTO A-3 class) and silty sand (AASHTO A-2-4 class). Following the local highway practices, the tests were conducted after compacting the soils and establishing Argentine Bahia turf over A-3 soils and Pensacola Bahia turf over A-2-4 soils. Two fertilizers were used: a quick release (QR) 10-10-10 and a slow release (SR) 16-0-8. Weather conditions varied considerably during the duration of the project, affecting soil moisture, soil—grass—nutrient interactions, ...

Effects of Deicing Salts on the Clogging of Stormwater Filter Media and on the Media Chemistry

AbstractStormwater filter media (SFMs) play a vital role in decreasing flooding and preventing urban contaminants from polluting surface and ground waters. The infiltration rate of a SFM is a governing factor in the hydrological and environmental performance of the stormwater management systems. This paper describes the effect of a common deicing salt (sodium chloride) in reducing the infiltration capacity of two types of SFMs, which were prepared using a clayey silty sand, one with compost and another without compost. This paper also describes the effect of sodium chloride application in the release of zinc, calcium, nitrogen, magnesium, phosphorous, potassium, and sulfur from the SFM, and whether their release was accelerated or reduced from the SFM with compost. Laboratory constant-head infiltration tests were conducted using sodium chloride (as the deicing salt) at concentrations of 150 and 1,200  mg/L. After conducting the tests for comparable cumulative pore volumes of infiltration, soil only SFM ex...

Engineered Waste Materials as Amendments to Prevent Erosion and to Stabilize Contaminated Sites

Erosion is an important consideration in remediation strategies of slopes at contaminated sites such as mine tailings. Pelletized waste materials offer the dual advantages of waste utilization and soil erosion prevention at such sites. These materials could be designed to reduce stormwater runoff by optimizing their infiltration capacities, to trap the eroded soil particles and pollutants before they get to the nearby lakes and streams, and store sufficient moisture for supporting vegetation. In this paper, we present the results of our study that focused on flow, erosion, and filtration through an erosion control blanket built with three different particle size ranges of pelletized waste materials. The finest gradation is used on the upper portion of the slope, and the medium and coarse gradations are used in the lower portions to act as graded filters for the upper portion. The density, gradation, and erodibility properties of the waste materials are used for calculating the flow, internal erosion, filtration, and moisture retention in the erosion control blanket. The model is intended to aid in the engineering design of erosion-resistant blankets on slopes. It optimizes the physicochemical and hydraulic characteristics of the pelletized waste materials to fulfill diverse functions of an erosion blanket, viz., erosion resistance, runoff inhibition, moisture retention to support vegetation, and controlled infiltration. INTRODUCTION Soil erosion is a world-wide problem that is causing early deterioration of public infrastructure, and pollution of surface and ground waters. As compared to vegetated landscapes, exposed soil slopes of earth structures and waste disposal sites experience 1047 World Environmental and Water Resources Congress 2009: Great Rivers