ahead of the advancing fill and overload the bulkhead causing its failure 

 before the landfill reaches it. The mud should be removed before fill 

 placement or the bulkhead designed for the increased pressures of the mud 

 wave. Care should also be taken to place select fill behind the bulkhead 

 before placing the general fill to ensure that the active pressure zone has 

 the shear strength planned in the design. 



Excessive turbulence in dumping fill material through water should be 

 avoided in order to prevent segregation of the materials or extremely flat 

 slopes at the edge of a fill. Uncontrolled bottom dumping from barges 

 through great depths of water will encourage segregation and spread fill 

 over a wide area. Berms or dikes of coarse-grained material or stone can 

 be used to confine the material. 



b. Compacted Fills . Where compaction of fills above the water level 

 is desired, either the method of compaction or the desired compaction can 



be specified. A test section is usually required to determine the effective- 

 ness of the methods before specifying a particular method. Otherwise, the 

 required density, moisture limits, and lift thickness are specified, allow- 

 ing the contractor some selection in compaction methods. 



Coarse-grained, cohesionless soils with less than 4 percent passing a 

 No. 200 sieve for well-graded soils, or with less than 8 percent for uniform 

 gradation, are generally insensitive to compaction moisture. These soils 

 should be placed at the highest practical moisture content and compacted by 

 vibratory methods. Where materials with sizes up to 150 millimeters (6 

 inches) maximum are used, the large sizes will interfere with the compaction 

 of soil smaller than a No . 4 sieve or 19-millimeter (0.75 inch) size. 

 Where large parts (more than 30 percent by weight) of gravel and cobbles 

 are present, a slight reduction (several percent) in the required density 

 of the sizes smaller than a No. 4 sieve may be tolerated. 



c. Hydraulic Fills. Hydraulic fills are placed on land or under water 

 by pumping material through a pipeline or by water sluicing through a con- 

 veyor. Borrow materials used for these fills are generally obtained by 

 dredging (Fig. 11). The characteristics of such hydraulic fills may be 

 generally classified according to the nature of the borrow material (Whitman, 

 1970) . This classification is shown in Table 4. 



Generally, material with more than 15-percent nonplastic fines or 10- 

 percent plastic fines passing a No. 200 sieve should not be placed under 

 water. The wash water for hydraulically placed fills on land should run 

 off in such a manner that fines are not concentrated in pockets. This may 

 require advancing the fill from one side or corner of the area, attempting 

 to force out any soft fines ahead of the fill as it is placed. Hydraulic 

 fills placed behind walls or bulkheads should be placed in lifts thin 

 enough to permit runoff of wash water without building up a full height of 

 hydrostatic pressure. 



Dredging and handling operations will produce significant textural 

 differences between original bottom sediments and sediments deposited at 

 the fill site. In general, these differences are an increase in the mean 

 grain size as fines are lost and a decrease in the uniformity coefficient 

 (see Table 2) of delivered versus bottom sands. The volumetric losses 



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