Review of continental shelf marine geotechnics: Distribution of soils, measurement of properties, and environmental hazards

Abstract

Sands and silty sands are the predominant surficial soils of continental shelves. Cohesive fine-grained soils are typical off the mouths of large rivers, near bays and estuaries, and in basins located on the shelf. The stratigraphy of shelf soils is very poorly known for most engineering purposes, except in the vicinity of the Mississippi Delta.Vibratory coring is the most common method of sampling shelf sands to depths of about 13 m; greater soil depths are sampled by borings often using drilling and wireline sampling tools. Employment of self-contained or wireline static cone penetrometers to obtain in situ measurements of sands has not been as common in the United States as in Europe. Dynamic piston corers are the most common samplers in cohesive soils, but rotary and hydraulically activated incremental corers are becoming available for marine use. Selfcontained or wireline vane shear devices and static cone penetrometers are used for the in situ testing of cohesive soils, and the latter device is also used for cohesionless soils. Dynamic cone penetrometers have been developed and have had limited experimental use at sea. In situ electrical resistivity and nuclear-transmission and backscatter probes have been used in cohesive soils to obtain bulk-

A budget for modern‐Holocene sediment on the South Otago continental shelf

“…The average density of Clutha silts (including mud) is 1.27 t m 3 as calculated by Thompson (1978). For sands, a bulk density of 1.8 t rrr 3 (Richards et al 1975) is assumed.…”

Regression analysis of physical and geotechnical properties of surface marine sediments

“…Sediment Properties. Physical and geotechnical properties of the sediments were measured in the laboratory following ASTM standards (ASTM, 1995) and previous studies (e.g., Boyce, 1976;Bryant et al, 1991;Head, 1980;Lee, 1985;Richards et al, 1975;Shephard et al, 1979). The properties measured in the laboratory included undrained shear strength, water content with salt correction, bulk density, void ratio, porosity, grain size, effective overburden pressure, and sound velocity.…”

The Benthic Boundary Layer

“…bottom currents affecting off-shore structures has been made by Richards et al (1975). A more detailed discussion of erosion and transportation has been made by Hollister and in the report of Group F in this volume.…”

“…Continental shelf geotechnics have been reviewed in general by Richards et al (1975) and by Bara (1974) specifically for the California shelf and continental borderland. Two regional geotechnical studies of bay sediments are by Mitchell (1963) on San Francisco Bay mud and Harrison et al (1964) on the Chesapeake Bay.…”