Gayle F Mitchell

Development of a CPT deployed probe for in situ measurement of volumetric soil moisture content and electrical resistivity

The authors have developed a Cone Penetration Testing (CPT) probe which measures both the resistivity and the dielectric constant of the soil. This method is innovative because the water relaxation effects due to interfacial polarization are greatly reduced. This effect has plagued previous researchers and resulted in inaccurate measurements of the soil dielectric constant. The design of our sensors consists of four concentric rings spaced along the penetration rod with insulators in between. The outer two rings determine the soil resistivity; the inner two rings measure the capacitance using a modified Clapp high-frequency transistor oscillator operating at 100 MHz. The CPT measured dielectric constant can be used to calculate the soil volumetric moisture content by directly calibrating to the soil of interest. A more general equation, such as Topp`s Universal Equation, can determine the volumetric moisture content. Details of the sensor design approach along with results from an extensive field evaluation at a DOE site follow. The field data presents soil moisture and resistivity measurements at three different sites on a DOE facility. These sites included measurements in the vadose and saturated zones. An extensive independent laboratory study was conducted to verify the accuracy and precision of the sensor.

Mitigating Highway Runoff Constituents via a Wetland

During rainfall/snowfall runoff events, constituents are conveyed from highway surfaces, which may degrade receiving water quality. Utilization of a natural wetland to mitigate storm water constituents from a portion of a 30,000-average-daily-traffic highway was studied. The runoff area consisted of two innermost lanes of a four-lane highway draining to a median drain via a vegetated median; a conduit conveyed this runoff into the wetland. Distributed runoff from the outermost lane along the wetland flowed across a vegetated highway embankment into the length of the wetland. During 57 rainfall-runoff events, in situ data collection included rainfall volume and frequency, conduit flow rate, and temperature, conductivity, pH, and dissolved oxygen. During each event, sequential samples were obtained and analyzed for metals, total suspended solids, and chemical oxygen demand from the wetland inlet and outlet. Flow-proportioned composite samples of sheetflow from the highway pavement edge were analyzed along with rainfall samples. Sediment samples were analyzed for metal constituents and organic material. Heavy metal concentrations in the storm water runoff consisted primarily of iron, zinc, lead, nickel, and copper. Concentration of metals was reduced via flow through the grassy median and then the wetland system. Over a 1-year study, average removals of heavy metals were 45% to 67%. First-order reaction rate constants were estimated to be 2.8,3.7, and 6 per day for iron, nickel, and zinc, respectively. Metals in bed sediments were representative of the hierarchy of concentrations analyzed in the runoff, and concentrations trended to increase with sediment organic fraction.

New Inspection and Risk Assessment Methods for Metal Highway Culverts in Ohio

This paper first describes Ohios new statewide culvert management program, which aimed to reduce the risk of structural failure of culverts that serve major highways. The paper next describes a research project conducted by the Ohio Research Institute for Transportation and the Environment (ORITE) research team at Ohio University to validate the effectiveness of the approaches outlined in the new program. The new culvert program is supported by high-resolution field inspection and rating procedures for concrete, metal, and thermoplastic culverts. This paper focuses on the metal culvert components of the research project. The new field inspection procedure for metal culverts was applied at 25 sites to detect problems common to many metal culvert sites in Ohio. The data produced during the field inspection phase were analyzed statistically to evaluate the effectiveness of the new procedure and to verify the findings made by the previous study about the conditions of the metal culverts that serve Ohios maj...

Modified direct shear study of clay liner-geomembrane interfaces exposed to landfill leachate

Abstract Direct shear tests have been utilized to quantify interface friction existing within the multi-layer solid waste landfill system. In this study, modified direct shear tests were performed for interfaces between compacted clay and three types of geomembrane materials (smooth HDPE, textured HDPE, and smooth PVC). Tests included clay samples saturated with leachate to simulate possible in-situ conditions in the landfill. Also, some geomembranes were submerged in leachate for up to 30 days prior to testing to simulate aging effect. Prolonged exposure of the geomembranes to the landfill leachate reduced the interface friction angle. The clay liner-PVC geomembrane interface was more susceptible to the leachate effect.

Prediction of brine application for pretreatment and anti-icing

Highway anti-icing strives to prevent the ice—pavement bond by pre-application of chemicals. An effective anti-icing program requires prediction and estimation of the amount, type, and timing of chemicals needed for the expected precipitation event while compensating for time and traffic decay of the chemical on the highway surface. Development of a sodium chloride brine anti-icing methodology was accomplished with an extensive study of brine residual decay on four pavement types. In October and November 2002, brine residual was monitored for up to 3 days after initial application on five sections of four-lane divided highways in Ohio. Four evenly spaced test stations within each highway section were monitored for residual as time passed and traffic accumulated. An instrument that dissolves salt and measures conductivity was used to measure available salt residual. Efficacy of the brine to prevent ice—surface bonding was estimated by using freeze—thaw cycles of various brines. After freezing, the bonds were held vertically as temperature was raised. The appearance of liquid below the interface indicated release. Field and laboratory data were correlated to estimate freezing temperatures for various salt residuals as a function of brine dilution represented by precipitation in depth of rainfall. Results support estimation of brine application requirements for three specific pavements based on expected precipitation and the salt residual models developed in the study. A set of graphs is included to implement the algorithm.

Decision Tree for Pretreatments for Winter Maintenance

This study addressed pretreatment protocol for winter maintenance of roadways using brine. Information on pretreatment was assessed from surveys of personnel in state departments of transportation and county garages in Ohio. Field durability studies of various applications of brine were conducted on portland cement concrete and asphalt concrete pavements in Ohio. Over three winter seasons, weather events and resulting pavement conditions were documented during pretreatment and during the subsequent events using visual assessment and limited road grip tester assessment. In addition, extensive laboratory studies were undertaken to supplement the field investigations. Integration of the findings resulted in a decision tree to aid in operational planning and pretreatment.

Removal, by Vegetated Biofilter, of Medium and Low Concentrations of Pollutants from Simulated Highway Runoff

The removal of pollutants by a prototype of a vegetated biofilter was investigated at medium and low concentrations. The biofilter was 4 ft (1.2 m) wide by 14 ft (4.3 m) long and was tilted at slopes of 8:1, 4:1, and 2:1. Artificial runoff, formulated with metals, native soil, and oil at medium concentration, was delivered at a rate equivalent to a simulated 2-year storm event (medium flow) at each slope; an additional experiment using a 10-year storm event (high flow) was conducted at the 2:1 slope. The flow rates at the low concentration represented 10-year storm events. During each simulated storm event, samples were obtained from the inlet, surface runoff, and underdrain and analyzed for total and dissolved metals, total suspended solids (TSS), and oil and grease. Before and after all tests, specimens were extracted from the bed and analyzed for metal content in soil, roots, and grass. Results indicated that all constituents (seven total metals and TSS) were removed at levels above 75% (event mean concentration) for medium-concentration influent. Metals above background levels were found primarily in the first half [7 ft (2.1 m)] of the bed. Oil removal was also achieved. Removals at low concentration were lower and erratic, and residual metal concentrations in the bed were near background levels. Soil particles in the influent flow, tagged with lanthanum, were neither resuspended nor measured at any significant concentration in the outlet surface flow.

INNOVATIVE USE OF THE CONE PENETROMETER TEST FOR HIGHWAY ENVIRONMENTAL SITE CHARACTERIZATION AND MONITORING

The cone penetrometer test (CPT) is an important tool for use in geotechnical and environmental site characterization for the transportation sector. Its role as both a primary investigation technique and as a component in an overall exploration strategy are explained. The types of sensors currently used with the CPT are discussed. Among the most promising new CPT technologies are a soil moisture probe and a fluorescence detection system. Laboratory and field results using a soil moisture probe jointly developed by Ohio University and Applied Research Associates for use with the CPT are presented. Also, application of the fuel fluorescence detector (FFD) for locating hydrocarbon contamination is presented, and typical data obtained with the FFD are illustrated and discussed.