Temperature Effects 



Typical seafloor temperatures are in the vicinity of 4°C. When a 

 sample is obtained and special precautions are not taken, the sample 

 temperature may rise by 30°C or more. This will result in water expan- 

 sion on the order of 0.5 percent. Since temperature changes occur 

 gradually, there is little chance of the grain structure being disturbed. 

 However, some water may be expelled. It has been shown (Mitchell, 1969) 

 that if the temperature is lowered again, the sample may appear stronger 

 or less compressible than it would have otherwise. Mitchell recommends 

 that testing should be performed at the highest temperature the soil has 

 ever experienced. 



Temperature also has been shown to have an influence on time-rate- 

 dependent soil responses (Singh and Mitchell, 1968) , such as secondary 

 compression and shear creep. When these soil responses are of critical 

 importance, samples should be maintained at seafloor temperatures con- 

 tinuously through the testing process. 



Organic Material Decomposition 



Seafloor soils often contain large quantities of organic material. 

 At seafloor temperatures, growth or decomposition of the material is 

 retarded. If the temperature of the sample is increased, the rates of 

 growth or decomposition may be greatly accelerated. Gases may be gen- 

 erated, and the properties of the soil may be altered. Richards and 

 Parker (1967) discuss core samples that have exploded on deck because 

 of gases generated during organic matter decomposition. Although core 

 sample explosions are rare, it is reasonable to assume that severe dis- 

 turbance may result from this phenomenon in many situations. 



Water Content Changes 



Samples can change their water contents through a variety of 

 mechanisms; included are pore fluid expansion, drying as a result of 

 improper sealing, and swelling as a result of storing the sample under 

 water. Since disturbance leads to increased sample compressibility, 

 partial consolidation within well-sealed core liners can also occur. 

 Vertical sample storage would probably lead to a greater amount of 

 consolidation than horizontal storage. 



Long-Term Storage 



A number of creep mechanisms can be operative over the long-term 

 period which would result in changes in the engineering response. 

 Vibrations (for example, from a refrigerator motor) could accelerate 

 creep rate. 



