Review of continental shelf marine geotechnics: Distribution of soils,measurement of properties,and environmental hazards |
| |
| Authors: | Adrian F Richards Harold D Palmer Michael Perlow Jr |
| |
| Institution: | 1. Marine Geotechnical Laboratory , Lehigh University , Bethlehem, Pennsylvania;2. Ocean Research Laboratory , Westinghouse Electric Corporation , Annapolis, Maryland;3. Wood‐ward‐Clyde Consultants , Plymouth Meeting, Pennsylvania |
| |
| Abstract: | 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. Self‐contained 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‐density and water‐content measurements and for stratigraphic correlation. Acoustical properties of cohesive and cohesionless soils have been measured by in situ probes and have been estimated from results of geophysical surveys made on ships that are under way. Environmental hazards to the foundations of offshore structures include earthquakes, wave‐induced loading and scour, and burrowing animals. Reported bottom‐current velocities on the United States continental shelf appear to have maximums of about 0.5 m/s under fair‐weather conditions and greater than about 5 m/s under hurricane conditions. Cyclical loading of the seafloor induced by storm waves appears to be a major hazard to soil stability in some areas. A representative sample of the widely scattered engineering and scientific literature of continental shelf marine geotechnics and geotechnically related subjects has been made to aid marine geologists, geotechnologists, and other specialists. |
| |
| Keywords: | Liquefaction Earthquake Hydraulic fill Coastal fill Harbor Marine soil mechanics |
|
|
