Concrete should be delivered to the pipeline smoothly and continu- 
ously and relatively free of pressure pulsations. A two-cylinder oil- 
hydraulic pump with a long stroke operating well below its maximum 
capacity can deliver concrete at a fairly constant pressure throughout a 
stroke and with a minimum of dead time between strokes. To further 
smooth out the pressure pulse, the pump can discharge into a pressure 
equalizing chamber and it, in turn, into the concreting head. 
The concreting head (Figure 3) provides a tightly sealed connection 
to the top end of the vertical pipeline and also provides a means for 
venting air, for inserting cleaning plugs, and for using a wire line, 
while maintaining pressure and flow of the concrete through the pipeline. 
The vertical pipeline for transporting the concrete to the seafloor 
is discussed in a later section. 
Seafloor Discharge Device. The function of the seafloor discharge 
system is to deliver the concrete underwater at the desired location in 
a coherent mass. Once flow has started, the concrete exit point is kept 
buried in the concrete already placed so that concrete is added to the 
interior of the mass. The mound grows by expansion in size from within 
rather than by addition of concrete on the surface of the mound. This 
procedure produces a compact mound with a minimum of washing out of 
cement or intermingling of concrete and seawater. The shape of the 
growing concrete mound is influenced by the properties of the concrete 
(such as slump), the discharge rate, the velocity of flow, and the depth 
of burial of the discharge point. The proposed 2- to 3-in. slump concrete 
will stand at a fairly steep angle. The velocity is reduced in the 
expansion chamber portion of the discharge device. The maximum depth of 
burial of the discharge point is maintained at 5 to 7 feet. (If the 
discharge pipe is buried too deeply, the concrete spreads out in a flat 
shape; if not buried deeply enough, the concrete wells up around the 
pipe and spills out on the surface.) 
A concept for a discharge device is shown in Figure 4. The velocity 
dissipation chamber has an increasing taper to prevent blockage by 
arching of aggregates. The tank-like "float" rides on top of the concrete 
once the mound has grown to several feet in height and thus maintains 
the discharge point at a fixed depth of burial as the mound continues to 
grow. The telescoping slip joint acts as a heave control device. The 
joint should accommodate up to 15 feet of vertical movement to decouple 
the discharge device from the pipeline. 
Auxiliary Equipment for Concreting. A small field laboratory 
should be provided in order to make tests of materials and fresh concrete 
for control purposes. 
Back-Up Equipment. System reliability is important for an at-sea 
operation. For a large job back-up equipment, particularly a concrete 
pump, should be provided. 
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