Appendix A 

 SOIL BIN PREPARATION 



The Seal Beach silt was obtained from a coastal mud flat in the 

 Long Beach, California, area. The material had a liquid limit of 49; 

 a plasticity index of 20; Unified Classification, ML; and Trilineal 

 Classification, clayey silt. The Rogers Lake clay is a commercial 

 product generally used as a drilling mud. The clay had a liquid limit 

 of 48; a plasticity index of 21; Unified Classification, CL; and 

 Trilineal Classification, clay. Grain size curves are presented in 

 Figure A-1. 



Two test bins were used, each 4-feet on a side by 2l2-feet deep. 

 A 3-inch thick porous sand-cement blanket was compacted and cured in 

 the bin bottom and connected to drain valves on the outside bottom of 

 the bins. The permeability of this filter was several times greater 

 than that of the test soils. 



The Seal Beach silt was prepared initially in a vertical two- 

 beater mixer with close-fitting container. The clayey silt was added 

 to the container followed by chlorinated seawater until a pourable 

 slurry, free of lumps, had been attained; then mixing was continued for 

 five minutes while a 25-inch Hg vacuum was applied to remove air 

 bubbles. The de-aired slurry was poured into the test bin through one 

 inch of seawater. Approximately 20 inches of de-aired slurry were 

 placed in the first bin. The silt slurry was consolidated by applying 

 a 9-foot head of water to the material via a siphon. Soil surface 

 settlement reached a negligible rate within three weeks , after which 

 the bottom drainage was discontinued, and the soil-water system was 

 allowed to reach equilibrium for two days. Final soil depth was about 

 13% inches. 



At the completion of the first and second test series, the Seal 

 Beach silt was covered with ten inches of seawater, and then was stir^ 

 red with a half-inch electric drill and paint mixer type blade to 

 return the soil to its original pourable slurry state. The consoli- 

 dation process using the siphon was then repeated. The mixing process 

 did entrain some air bubbles, such bubbles could be seen breaking at 

 the slurry surface. 



The Rogers Lake clay was mixed in a double planetary mixer without 

 vacuum de-airing to a pourable consistency. The as-delivered clay 

 product consisted primarily of dried clay lumps; these lumps were 

 broken down by mixing in tap water with calcium hexametaphosphate added 

 as a dispersant. Subsequently C.P. grade sodium chloride was added to 

 the slurry in the amount of 35 ppt. The method of placement of the 

 clay slurry in the second bin was the same as for the first placement 

 of the clayey silt except that a number of air bubbles could be seen 

 breaking at the surface. No seepage force was applied to the clay; 

 instead the pressure head at the base of the soil was maintained at the 

 level of the water surface over the soil. The purpose of this procedur- 

 al change was to obtain a soil strength versus depth profile which 



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