Liquefaction Response Research Articles

Geotechnical Studies in the Baltimore Canyon Trough Area

Summary This paper presents the results of a site investigation, the onshore laboratory testing program, and the interpretation of data from the standpoint of application and hazard. The study site was generally between the Atlantic Outer Continental Shelf (OCS) exploration leases in the Baltimore Canyon trough and potential markets on the U.S. east coast. Conclusions indicate that the shallow marine sediments from the Baltimore Canyon trough corridor area are typical of terrestrial soils from adjacent shore areas. Introduction Potential for future development on the Atlantic Potential for future development on the Atlantic OCS requires that the U.S. Bureau of Land Management anticipate where development may be proposed and conduct appropriate studies. These proposed and conduct appropriate studies. These studies include those by the USGS that are concerned with the evaluation of geological hazards. Current interest and activity in the Atlantic OCS centers on exploration drilling in the Baltimore Canyon trough area. In addition to the drilling locale itself, the routes for communication between the drilling sites and shoreline facilities should be studied. If commercial quantities of oil or gas are discovered in the Baltimore Canyon trough area, transport to shore most likely will be through pipelines supported in or on the sea bottom. This study is concerned with evaluating the engineering characteristics of the sediments and any potential hazards within a representative transection across the continental shelf in the Baltimore Canyon trough area. To collect specific information for the study, a cruise was conducted by the USGS using the R/V Annandale during Sept. 18-25, 1977. During the cruise, 20 vibracores were collected at 17 stations across the shelf in water depths of 35 to 70 m (Fig. 1). Immediately after the cruise, the cores were taken to the laboratories of Geotechnical Engineers Inc. of Winchester, MA. There, an extensive series of geotechnical engineering tests were carried out on the cores; these data are the basis of this report. Geotechnical engineering properties traditionally have been part of site-specific studies, such as for a particular platform location rather than as part of a particular platform location rather than as part of a regional survey. However, knowledge of geotechnical engineering properties can be applied in several different ways to regional investigations such as in the Baltimore Canyon trough area. The most obvious application is in the evaluation of geologic hazards. Many hazards are associated directly with an engineering characteristic of the marine sediments. For example, the potential for liquefaction or other undesirable response to dynamic loading is a characteristic of the natural sediments. Hazards associated with soft, compressible sediments or with low shearing resistance also can be evaluated on a regional basis. The key to applications such as these is to collect and test specimens that are representative of identifiable geologic formations or units. It then is necessary to interpret the test results in a way which allows rational extrapolation or interpolation throughout the geologic unit. Geotechnical engineering properties frequently are not fixed quantities (such properties frequently are not fixed quantities (such as specific gravity) but are variable with time or environmental location. The shearing resistance of a particular sediment, for example, is not a fixed particular sediment, for example, is not a fixed quantity. It will vary depending on environmental stress level (depth below sediment surface), stress history (previous erosion or deposition), and time. Use of geotechnical engineering test results in regional studies is most valuable if these factors are considered in the analysis.