Geologists have investigated many different types of subsidence (Table 1) in North America during the past 100 years. Their principal contribution has been a better understanding of subsidence processes associated with the sudden formation of sinkholes, volcanic activity (Schuster and Mullineaux, this volume), tectonism (Bonilla, this volume), and sediment compaction induced by withdrawal or natural expulsion of underground fluids. Although major advancements in the understanding of other types of subsidence processes have been made primarily by engineers and soil scientists, geologists have outlined the geologic framework within which these subsidence processes are active. Allen (1969) provides an overview of the geologic processes that contribute to subsidence and the geologic setting of subsidence.
This chapter traces the evolution during the past 100 years of the conceptual understanding of land subsidence in North America caused by compaction of unconsolidated sediment induced primarily by the withdrawal of underground fluids. It reviews the ways these concepts have been applied, both to development of the theory of fluid flow through porous media and to gain insight into natural geologic processes. Four important case histories are examined, and the chapter concludes with discussions of the outlook for future investigations of subsidence in North America and a summary of research needs. Terminology used in the chapter follows Poland and others (1972).
Subsidence associated with man-induced compaction is one of man’s major inadvertent engineering feats. At least 34 areas in Mexico and the United States have subsided (Fig. 1); an aggregate area of about 22,000 km2, approximately equal to the area of New Jersey, has been lowered more than 30 cm.
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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.