DATA REDUCTION 



The data from the strip chart recordings (Figure 8) were digitized 

 and used to calculate the friction ratio, which is the ratio between the 

 sleeve friction and the cone pressure. This friction ratio is usually 

 expressed as a percent. The cone pressure and friction ratio data were 

 then plotted as a function of depth. Examples of these plots are given 

 in Figures 10 and 11. Before forming the friction ratio, the sleeve 

 friction and cone pressure readings were corrected to a common depth 

 point by assuming that the measured cone pressure represents the 

 behavior of sediment at the cone tip and that the friction stress repre- 

 sents behavior at the center of the friction sleeve which is 3 inches 

 above the cone. Using these plots, soil profiles were developed over 

 the depths of penetration using Figure 12 (a chart of soil type as a 

 function of cone pressure and friction ratio). This chart was derived 

 by Martin and Douglas (1981) for determining stratigraphy from data 

 taken with electrical friction cover. Details on reducing the data are 

 provided in the Appendix. 



TEST RESULTS 



Norton Sound, Alaska 



During the summer of 1981, a total of 40 soundings were made with 

 the XSP in the 20-foot mode at the Norton Sound test site off the west 

 coast of Alaska. National Oceanic and Atmospheric Administration's 

 (NOAA) ship R/V DISCOVERER was used as the support vessel. In deploy- 

 ment from this ship, the XSP was hung horizontally over the side of the 

 ship from a pair of davits (Figure 7). 



All of the soundings were made without jetting because the cone 

 unit with the jetting nozzle was broken off and lost on the first 

 sounding. The backup cone (a penetrometer tip only) was fitted to the 

 push rods and used to perform the remaining soundings. With this pene- 

 trometer tip, water jetting was not possible because the cone unit was 

 not complete because it did not contain a jetting nozzle (see Figure 3). 

 No problems were encountered while performing the remaining 39 

 soundings. 



The soils encountered at the test site were very dense, limiting 

 penetration to between 1.6 and 12 feet. Multiple soundings were made at 

 most sounding locations, and the data were consistent between replicate 

 soundings. Most of the sounding locations were also subsequently 

 sampled with a vibratory corer and these cores compared well with the 

 XSP data. 



Within the test site, five areas were selected for the XSP 

 soundings. These areas, shown in Figure 13a, were selected to provide 

 coverage of the Norton Sound area and to cover in some detail areas that 

 may be involved in processes potentially hazardous to offshore develop- 

 ment. These potential geologic hazards — gas charging, wave-induced 

 li qui faction, and ice gouging — were first detected by high resolution 

 seismic profiling, side seam sonar, and geochemical and geological 

 evaluation of soil cores. Reliable in-situ data were needed to quanti- 

 tatively evaluate the hazard potential; thus the XSP was used. 



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