Engineering Commons^™

Evacuee Route Choice Decisions In A Dynamic Hurricane Evacuation Context, R. Michael Robinson, Asad Khattak

VMASC Publications

Very high traffic volumes may lead to extensive congestion during hurricane evacuations. Evacuation planners reduce this congestion by careful planning for multiple hurricane scenarios and assignment of evacuation routes and timing. This planning may be for naught if obstructions block key roadways. An advanced traveler information system (ATIS) may be used to guide evacuees to alternate routes, but how effective will that guidance be? Should the use of alternate routes be encouraged? How are drivers likely to respond to delays and information? Will information shorten or improve the reliability of travel times in emergency conditions? Integration of a dynamic evacuation …

Resilient Modulus Of Compacted Crushed Stone Aggregate Bases, Tommy C. Hopkins, Tony L. Beckham, Charlie Sun

Kentucky Transportation Center Research Report

In recent years, the American Association of State Highway Transportation Officials (AASHTO) has recommended the use of resilient modulus for characterizing highway materials for pavement design. This recommendation evolved as result of a trend in pavement design of using mechanistic models. Although much progress has been made in recent years in developing mathematical, mechanistic pavement design models, results obtained from those models are only as good as the material parameters used in the models. Resilient modulus of aggregate bases is an important parameter in the mechanistic models. The main goal of this study was to establish a simple and efficient …

Characteristics And Engineering Properties Of The Soft Soil Layer In Highway Soil Subgrades, Tommy C. Hopkins, Tony L. Beckham, Liecheng Sun

Kentucky Transportation Center Research Report

The objective of this research was to examine the conditions and characteristics of soil subgrades that had been stabilized using mechanical compaction. Goals of the study are to identify and examine the engineering properties and behavior of the “soft layer’ of material observed at the top of untreated, highway pavement soil subgrades. Alternative methods of preventing, or mitigating, the development of the soft layer are discussed.

Evidence is presented that shows that a soft layer of soil frequently develops at the top of untreated, highway soil subgrades. Data are presented that show strengths obtained from mechanical compaction are largely destroyed …

Long-Term Benefits Of Stabilizing Soil Subgrades, Tommy C. Hopkins, Tony L. Beckham, Liecheng Sun, Bixian Ni, Barry Butcher

Kentucky Transportation Center Research Report

Chemical admixtures have been used extensively since the mid-eighties in Kentucky to improve bearing strengths of soil subgrades. Most pavements in Kentucky are constructed on clayey soils. Although short-term observations at a small number of sites showed that chemical stabilization worked very well, a need existed to perform a more comprehensive review and to assess the long-term benefits of this subgrade stabilization method. The main intent of this study was an attempt to address questions concerning bearing strengths, longevity, durability, structural credit, economics, and performance of pavements resting on soil subgrades mixed with chemical admixtures. In-depth field and laboratory studies …

Resilient Modulus Of Kentucky Soils, Tommy C. Hopkins, Tony L. Beckham, Charlie Sun, Bixian Ni

Kentucky Transportation Center Research Report

In recent years, the American Association of State Highway Transportation Officials (AASHTO) has recommended the use of resilient modulus for characterizing highway materials for pavement design. This recommendation evolved as of a result of a trend in pavement design of using mechanistic models, which are based on the theory of elasticity (layered elastic analysis) or linear and non-linear, finite elements (and finite difference methods), or a combination of both of those theoretical approaches. Although much progress has been made in recent years in developing mathematical, mechanistic pavement design models, results obtained from those models are only as good as the …

Bearing Capacity Analysis Of Pavements, Tommy C. Hopkins

Kentucky Transportation Center Research Report

A multilayered, mathematical model for analyzing the ultimate bearing capacity of soil subgrades and asphalt pavements is presented. Theoretical considerations and mathematical derivations of limit equilibrium equations, based on plasticity principles, for analyzing the ultimate bearing capacity of soil subgrades and partially completed asphalt pavements, and the extension of these equations to the analyses of asphalt pavements composed of multiple layers, are presented. The model is unique since shear strength parameters, Φ and c, (the angle of internal friction and cohesion, respectively) are used to describe each layer of material of the pavement structure and a factor of safety against …

Stability Of Embankments On Clay Foundations, Tommy C. Hopkins

Kentucky Transportation Center Research Report

Ninety-one well-documented geotechnical failures are reviewed. The case studies involved the failure of embankments, footings and load tests, excavated slopes, and natural slopes. Seventy-five of the geotechnical failures had been analyzed using total stress analysis. Sixteen of the case failures had been analyzed using effective stress analysis. Based on a review of these case studies, there are discrepancies between predicted and actual stabilities of geotechnical structures and there is a tendency tu overestimate the factor of safety. Differences that may arise between predicted and actual performances are discussed and examined and guidelines are proposed for evaluating the potential of successfully …

A Generalized Slope Stability Computer Program: User’S Guide For Hopk-I, Tommy C. Hopkins

Kentucky Transportation Center Research Report

Data entry and operation of a generalized slope stability computer program are described. The computer program is based on a new approach to formulating and solving the slope stability equilibrium equations. The moment equation as well as the horizontal and vertical equilibrium equations are considered in the model. The purpose of the study was to implement the new approach. The computer program may be used to compute the factor of safety of slip surfaces of arbitrary shape and circular slip surfaces. Effective stress and total stress conditions may be analyzed. Four options are available for computing pore pressures. Both piezometric …

Effectiveness Of Traffic Noise Barrier On I 471 In Campbell County, Kentucky, Tom Creasey, Kenneth R. Agent

Kentucky Transportation Center Research Report

The objective of this study was to evaluate the effectiveness of the traffic noise barrier on I 471 in Campbell County, Kentucky. Since the barrier coincided with construction of I 471, it was necessary to predict noise levels that would exist if no barrier were present utilizing the FHWA STAMINA 2.0 computer model. This was compared to actual noise level measurements at the barrier site to determine the barrier insertion loss.

After calibration of the STAMINA 2.0 model, noise measurements were conducted at 39 receiver locations during off-peak and peak traffic conditions. The noise barrier reduced the noise level reaching …

Unstable Subgrade, I 65, Hardin County (I 65 - 5 (17) 92; Fsp 047-0065-091-0396), Tommy C. Hopkins, Gary W. Sharpe

Kentucky Transportation Center Research Report

During construction of the southbound lanes of I 65, Stations 120+00 to 218+00, in Hardin County, Kentucky, near Elizabethtown, large deformations were observed when dense-graded aggregate (DGA) base courses were loaded with construction traffic. Rutting and cracking of the DGA also was noticeable. A study was performed to determine the causes of the unstable subgrade and base, recommend remedial actions, and evaluate the effectiveness of the remedial measures. The stability, or bearing capacity, of the unstable pavement was determined for different construction stages and combinations of pavement layer thicknesses using a relatively new stability model HOPK-I. The stability of the …

Effectiveness Of Traffic Noise Barrier On I 471 In Campbell County, Kentucky (Interim Report), Tom Creasey, Kenneth R. Agent

Kentucky Transportation Center Research Report

The objective of this study is-to evaluate the effectiveness of the traffic noise barrier on I 471 in Campbell County, Kentucky. Since the barrier construction coincided with construction of I 471, it was necessary to predict noise levels that would exist if no barrier were present by utilizing the FHWA STAMINA 2.0 computer model. This was compared to actual noise level measurements at the barrier site in order to determine the barrier insertion loss.

After calibration of the STAMINA 2.0 model, initial field measurements were taken at receiver locations throughout the barrier site. The average insertion loss in Leq was …