Engineering Geology - A2L05: Committee on Engineering...

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A2L05: Committee on Engineering Geology Chairman: John D. Duffy Engineering Geology J OHN D. D UFFY , California Department of Transportation J EFFREY R. K EATON , Engineering geologists are concerned with the distribution and relevance of earth materials; potentially dangerous naturally occurring and human-induced geologic hazards; and assessment of the risks of damage and injury associated with those hazards as they can be quantified for application to the planning, location, design, construction, and maintenance of transportation systems. During the 20th century, these concerns have been addressed in part by landmark publications in the Transportation Research Board’s Special Report series on landslides, first published in 1958, updated in 1978, and appearing most recently in 1996 as Special Report 247, Landslides: Investigation and Mitigation . Similar efforts are expected to serve engineering geologists in the new millennium. STATE OF THE PRACTICE Conventional methods of documenting and mapping earth materials for transportation projects are based on direct observation, with notes being made directly onto maps and aerial photographs. Current state-of-the-practice exploration techniques include mapping regional features at small scale and detailed features at large scale. Mapping done directly on aerial photographs can be transferred to planimetric maps using plotting devices that are rapid and accurate. Low-sun-angle aerial photographs are being used to enhance the definition of fault and landslide scarps for field identification. Interpretations of earth material distribution and evidence of relevant geologic processes, along with effective communication of these interpretations, remain among the most significant of challenges for engineering geologists. Many transportation systems face a variety of potentially hazardous natural processes. In their attempts to deal with these hazards in a responsible way, state departments of transportation are using engineering geologic procedures to identify and rank specific hazards so that cost-effective remediation plans can be formulated. Litigation is a driving force in some cases as natural processes are being more closely scrutinized, and the public expects departments of transportation to be able to control the associated hazards. Rockfalls and scour at bridge sites are two such processes that have been addressed systematically in the 1990s. Remedial measures applied to soil and rock slopes and facilities for containing or controlling sediment discharge from stream channels and on alluvial fans are being evaluated in terms of their effectiveness and longevity. The performance of steel rock bolts applied to improve the stability of some highway slopes since the 1960s is being assessed relative to the long-term maintenance of the slopes and corrosion of the rock bolt elements. Slope treatment measures, such as wire and cable drapery systems, and corridor protection
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Engineering Geology - A2L05: Committee on Engineering...

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