Criteria for Design of Pavement Thicknesses, Kentucky Interstate Highways

The Kentucky Department of Highways, in 1946, sought a more systematic criteria and basis for designing the thickness of bituminous concrete pavements. The Research Division was authorized to pursue this work and to develop the criterion. These efforts were embodied in a report (1) to the Department, which offered a system of design based upon CBR\u27s and EWL\u27s. EWL\u27s were computed originally for a 10-yr. period but this practice was revised in 1954, to encompass 20-yr. traffic (more realistic with respect to average road life). Then, in 1957, the Department requested a re-evaluation of the criteria from the standpoint of experience and performance of pavements designed thereby. This re-study and recommendations was reported to the Department and to the Highway Research Board (2)(3). A copy of current design chart is shown on the following page (Fig. 20, ref. 2 and 3)

Kentucky’s Pavement Management System

Pavement management concepts are discussed, and a method is presented illustrating the required data and its use to accumulate EAL\u27s annually for comparison with the design EAL. This method can be used to determine overlay priorities, overlay design thicknesses, and financing schedules. A discussion of automatic feedback of field data is presented. Pavement condition reports should be analyzed separately to prevent improper adjustments in the design system due to causes of failure other than normal fatigue. An overlay, whether for extending service life or improving skid resistance, provides an additional structural thickness and will modify the design life. Preparation of the R-R-R cost estimates in the fall of 1976 offered the opportunity, and necessity, to implement a pavement management scheme. The methodology used to prepare the cost estimates are discussed in relation to overlay design and scheduling of resurfacing on the Interstate System in Kentucky. There are compounding and confounding factors which may distort pavement performance and confuse a pavement management scheme based only on the structural adequacy of the pavement. Such factors and influences as D-cracking, expansive aggregates, ditching, skid resistance, roughness, and rutting are discussed

Re-evaluation of the Kentucky Flexible Pavement Design Criterion

Prior to 1948, the criterion in Kentucky for designing the thickness of bituminous pavements was based upon a modified laboratory CBR and the 1942 curves developed by the California Department of Highways. In 1948, the Materials Research Laboratory reported: An Investigation of Field and Laboratory Methods for Evaluating Sub-grade Support in the Design of Highway Flexible Pavement. Included in that report as a recommended method of thickness design for use in Kentucky was a set of curves based upon an empirical relationship between minimum laboratory CBR and observed pavement performance. These five curves accounted for traffic groups up to 10,000,000 EWL\u27s. Since that time six additional curves have been included in the de sign charts for EWL groups up to 320,000,000. These additional curves were determined by extrapolation of the results from the 1948 study. Early in 1957, an evaluation of the design method was under taken. The basis for this re-evaluation was a statistical comparison of actual pavement performances with the designed life as anticipated or predicted by the design curves currently in use. On this basis, projects were selected, design records assembled, performances surveyed, and the data analyzed. Selected pavements which had been designed by the method developed in the 1948 study were checked for performance by visual survey, by roughness measurements, by measurements of rutting, by measurements of loaded-deflection with the Benkelman Beam, and by opening pavements for observation and sampling. Flexible base types studied included water bound macadam, bituminous concrete, granular dense graded aggregate and combinations. Laboratory evaluation on basis of bearing tests were made. The visual survey established a range of performance. Road roughness measurements were related to CBR but no attempt was made to draw design curves from this data since it could be greatly affected by factors not related to structural design. Pavements opened for inspection revealed permanent deformation in the upper layers of the system as well as intrusions of subgrade in waterbound base courses. An alternate method of design based on limiting deflection under load was developed from the Benkelman Beam measurements. Curves drawn from this data indicate a need for a slightly greater thickness than provided by the 1948 curves

Ten Rural Highway Base Stabilization Projects

During the last week o£ September, 1956, the Division of Rural Highways requested assistance from the Research Division in conducting a series of ten experimental base stabilization projects which were to be geared more-or-less to a practical rural roads development program in which existing soils and local granular materials might be most advantageously treated and stabilized to provide fairly low cost base courses and surfaces, adequate for light rural traffic. The idea of actually constructing a base and bituminous surface for this type of road would represent a refinement over the traditional traffic-bound base type of construction which usually serves as a preliminary to light bituminous surfacing. While the traffic-bound type of construction has been used effectively in the past, there seems to be an inherent impatience on the part of property owners and general public to get on to the bituminous surfacing stage before the traffic-bound base has fully stabilized. In several such instances it has been necessary to add extra surfacing within a year or so, or else to revert to the traffic-bound stage again and start over

Concrete, Bridge Decks: Deterioration, Coatings and Repairs

This report is not wholly a culmination of a planned or programmed research project. It is a historical account of damage sustained by both new and old concrete bridge-decks -- through freeze-thaw, salt action, etc, -- and of some expedient repairs which have been effected. The problem of durability in concrete bridge-decks has become increasingly critical during the past ten years or so and is now a major concern to highway engineers throughout the northern tier of states. While there is not yet a concerted agreement in regard to the cause of the trouble, relief is being sought through improved construction practices, air-entrainment, and protective coatings of various kinds. Similarly, relief from perpetual maintenance or complete replacement of existing bridge decks is being sought through improved methods for making repairs. The performance of individual slabs in a deck is sometimes markedly different from that of a nearby slab; and, even within a particular slab, only one corner or one end may be affected. This signifies poor concreting practices. The concrete sustaining damage was undoubtedly over-watered, over-worked, de-aired, and segregated. The proper placement of deck concrete is perhaps the more serious aspect of the problem than the repair, because improper placement automatically incurs a premature maintenance liability. Of course, as the need for repairs arises in due time, reliable methods of repair should be employed. It is in this latter respect that the repair experiences recorded in this report are expected to be the most fruitful. None of the damaged decks which have been observed thus far has shown any evidence of overloading by traffic (adjudged by the absence of any checker-board crack-pattern on the underneath side of the deck); the trouble seems to be attributable almost entirely to weathering; and the weathering invariably seeks out and attacks the poorest concrete often revealing the mistakes made by the workmen and their attempts to hide them. Improper drainage of the deck and gutter can be one of the contributing factors to damage. Even slabs and gutters sometimes have bird-baths in them. Cinders, sand, road-debris, and snow sometimes impound water and prevent drying. Such areas are exposed to water and moisture beyond their normal time and damage is often associated with these conditions

Healthcare Contact and Treatment Uptake Following Hepatitis C Virus Screening and Counseling Among Rural Appalachian People Who Use Drugs

Background—Hepatitis C virus (HCV) remains a major contributor to morbidity and mortality worldwide. Since 2009, Kentucky has led the United States in cases of acute HCV, driven largely by injection drug use in rural areas. Improved treatment regimens hold promise of mitigating the impact and transmission of HCV, but numerous barriers obstruct people who inject drugs (PWID) from receiving care, particularly in medically underserved settings. Methods—503 rural people who use drugs were recruited using respondent-driven sampling and received HCV screening and post-test counseling. Presence of HCV antibodies was assessed using enzyme immunoassay of dried blood samples. Sociodemographic and behavioral data were collected using computer-based questionnaires. Predictors of contacting a healthcare provider for follow-up following HCV-positive serotest and counseling were determined using discrete-time survival analysis. Results—150 (59%) of 254 participants reported contacting a healthcare provider within 18 months of positive serotest and counseling; the highest probability occurred within six months of serotesting. 35 participants (14%) reported they were seeking treatment, and 21 (8%) reported receiving treatment. In multivariate time-dependent modeling, health insurance, internet access, prior substance use treatment, meeting DSM-IV criteria for generalized anxiety disorder, and recent marijuana use increased the odds of making contact for follow-up. Participants meeting criteria for major depressive disorder and reporting prior methadone use, whether legal or illegal, were less likely to contact a provider. Conclusion—While only 8% received treatment after HCV-positive screening, contacting a healthcare provider was frequent in this sample of rural PWID, suggesting that the major barriers to care are likely further downstream. These findings offer insight into the determinants of engaging the cascade of medical treatment for HCV and ultimately, treatment-as-prevention. Further study and increased resources to support integrated interventions with effectiveness in other settings are recommended to mitigate the impact of HCV in this resource-deprived setting

Calculating the Velocity of a Fast-Moving Snow Avalanche Using an Infrasound Array

On 19 January 2012, a large D3 avalanche (approximately 103 t) was recorded with an infrasound array ideally situated for observing the avalanche velocity. The avalanche crossed Highway 21 in Central Idaho during the largest avalanche cycle in the 15 years of recorded history and deposited approximately 8 m of snow on the roadway. Possible source locations along the avalanche path were estimated at 0.5 s intervals and were used to calculate the avalanche velocity during the 64 s event. Approximately 10 s prior to the main avalanche signal, a small infrasound signal originated from the direction of the start zone. We infer this to be the initial snow pack failure, a precursory signal to the impending avalanche. The avalanche accelerated to a maximum velocity of 35.9 ± 7.6 m s−1 within 30 s before impacting the highway. We present a new technique to obtain high spatial and temporal resolution velocity estimates not previously demonstrated with infrasound for avalanches and other mass wasting events

Some Chemical, Physical and Mineralogical Features of Soil Colloids

The -1 micron portion of several diversified soils were separated by sedimentary fractionation. Physical properties were evaluated on the -1 micron portion, the +1 micron portion, and on the original -40 sample. The -1 micron portion was analyzed for clay mineral identity by X-ray diffraction, and analyzed chemically for associated materials such as the oxides of Iron, Aluminum, Calcium, and lv!agneeium. These data present several possibilities and trends as to the inter-dependency of the involved variables, other considerations have been devoted to the geologic origin of several samples and to various physico-chemical relationships

Kentucky Research: A Flexible Pavement Design and Management System

Various strategies for designing pavement structures are discussed. Initial full-life design, stage designs and planned extensions of service life, final design, surface renewals for deslicking, no-defect designs for high-type high-volume facilities, and allowable-defect designs are considered. Economics enter in terms of salvage value of existing pavements and alternate designs using different proportions of materials within the structure. The elastic model represented in Chevron\u27s n-layered computer program is the basis for theoretical relationships. Ranges of values are given for input variables such as Young\u27s moduli, Poisson\u27s ratio, thicknesses for layers, tire pressure, and load. The Kentucky CBR is related to modulus by E = 1500 x CBR and is correlated with the AASHO Soil Support value and other strength relationships. The modulus of crushed stone base is shown to be a function of the moduli of the asphaltic concrete and sub grade. Appropriate relationships are given