Construction Materials and the Environs of Engineering Works
Today, glaciers cover 10 percent of the Earth’s land area, whereas 30 percent was covered during the maximum glaciation of the Quaternary Period. Although 20 percent of the Earth’s surface has a direct glacial heritage, another 12 percent was impacted by glacially related climates and sediments. Moreover, wind-blown silt, or loess, and long-travelled outwash have also affected many terrains, as in China, eastern Europe, and the Missouri-Mississippi Valley region. The glacial deposits that cover 10 million km2 in North America have profoundly influenced the terrain and must be accounted for when making land-use decisions, whether for agriculture, urbanization, or planning and construction.
The applied geological scientist must consider and understand the vast differences that occur in the many different types of glacial deposits in order to successfully utilize the natural materials and/or sites for man’s use and his engineering works. Each of the different glacial sediments, whether till, ice contact, or outwash, will exhibit different physical characteristics when subjected to man-induced changes. These different properties become manifest when the deposits are exposed in excavations, bearing loads are emplaced, or the material is utilized for construction purposes. Furthermore, there are many dissimilarities among glacigenic sediments even within broad categories. For example, lodgement till has entirely different values of consolidation, permeability, and density than either melt-out till, or flowtill. Many failures of engineering works have occurred when these quality differences have not been recognized in the field (see Kiersch, chapters 1 and 22, this volume).
Glacial deposits create their own landforms and landscapes, and proper identification of these terranes can prove important to the applied geologist.
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A review of milestones and changes in geological theory and practice from which modern engineering geology in North America has developed. Five chapters discuss historical events and the contributions of early scientists and engineers; nine chapters review the state of knowledge of dominant geologic processes, phenomena, and specialized principles critical to modern practice; and three chapters discuss geologic environs and the properties of construction materials. Four chapters are devoted to geoscience investigations and related techniques for: initial regional-areal evaluation of conceptual candidate sites (Phase I); selection of preferred-designated sites and design (Phase II); typical kinds of investigations used during project construction (Phase III); and as-built documentation and explorations of the operating or rehabilitation phases. Closing chapters focus on the geoscientist's responsibilities relative to engineering failures, errors of judgment that impact works, litigation, and forensic geoscience. The 34 contributors present extensive case histories applicable worldwide.