SELECTION OF DESIGN STRENGTHS OF UNTREATED SOIL SUBGRADES AND SUBGRADES TREATED WITH CEMENT AND HYDRATED LIME
Selection of design strengths of soil subgrades and subgrades treated with cement or hydrated lime is a problem in pavement design analysis and construction. Different types of soils may exist in a highway corridor and different strengths may exist after the soils are compacted to form the pavement subgrade. The selected subgrade strength will largely affect the pavement thickness obtained from the design analysis, future pavement performance, and the overall bearing capacities of the subgrade during construction and the pavement structure after construction. In developing the proposed selection scheme, a newly developed mathematical model, based on limit equilibrium, is used. Relationships among undrained shear strength [or California bearing ratio (CBR)] and tire contact stresses are developed for factors of safety 1.0 and 1.5. The minimum subgrade strength required to sustain anticipated construction tire contact stresses during construction is determined. A criterion is proposed for determining when subgrade stabilization is needed and methods of selecting the design subgrade strength are examined. A least-cost analysis appears to be an appropriate approach as shown by analysis of a case study involving pavement failures. Two case studies show that soaked laboratory strengths appear to be fairly representative of long-term field subgrade strengths. Hence, using soaked laboratory strengths and least-cost analysis appears to be a reasonable means for selecting the design strength of subgrades for pavement analysis. To avoid failures of chemically stabilized layers, relationships among thicknesses of chemically treated layers and the CBR values of the untreated subgrade for a factor of safety of 1.5 are presented.
Developing a Byproduct Materials Information System for the Kentucky Transportation Cabinet
Kentucky has numerous coal-fired, electric generating facilities and, as a result, there are abundant byproduct materials being produced from these facilities that have environmental, engineering, and economic potential as materials for use in common highway construction and maintenance related activities throughout the Commonwealth. Other byproduct materials are being produced and are available that may have potential uses as well. Although large quantities of byproduct materials are produced in Kentucky and many of those materials have positive or neutral environmental impacts and excellent engineering properties, a formal regulatory framework for selecting, characterizing, recovering, and recycling these material types does not exist. Fundamentally, the lack of a regulatory protocol is an obstacle to recycling byproducts and discourages the use of byproduct materials by the Kentucky Transportation Cabinet. During this research effort, a byproduct materials information system was developed to guide the selection and use of ponded ashes in highway construction and maintenance activities. The information system was designed to be modular so that additional recovered and recyclable materials could be included within the matrices as these materials are evaluated at some future date. It is fully anticipated that the byproduct information system eventually will encompass any recovered or recycled materials that are shown through the prescribed method of evaluation to possess satisfactory environmental, engineering and economic characteristics that make them suitable for use in highway construction and maintenance activities.
PASSIVE AND LOW-ENERGY RESEARCH AND PRACTICES-DEHUMIDIFICATION
Methods of achieving acceptable indoor conditions in overheated, temperate, and underheated humid climates are discussed and compared. Desiccants and desiccant systems utilizing solid and liquid sorbents and various low-energy mechanical systems are described and evaluated.