Volume Twelve - Pre-Victorian to the Present Day - further aspects - Report upon Penarth Dock - 1984 . . .

The gate floors over which the dock gates moved formed a flat surface which was paved with masonry. Each gate floor was equipped with two circular cast-iron plates upon which the rollers at the bottom of each gate travelled. The gate floor was designed to withstand the weight of the gates and also to resist the scouring action of the sluices.

The aprons were positioned at the extreme ends of both the lock and sea entrance. Those at the inner ends were intended to resist the scouring action of water entering the sluiceways whilst those at the outer ends were intended to resist the scouring action of water leaving the sluiceways. The aprons were probably constructed of masonry and formed shallow inclined planes leading down from either end of the lock and sea entrance.

4.1.3 - Side Walls

The walls at either end of the lock and sea entrance fulfilled more-or-less the same purpose as the other dock walls and in general had similar cross-sections to the solid walls already discussed. However, beyond the inner gates they were subjected to the changing pressure due to to the rise and fall of the water level.

This varying strain was compensated for by the invert and the floor which prevented the side walls from sliding forward. The structure of the side walls diverged from that of the dock walls in the area around the back of the dock gates. This was for four main reasons, namely, the thrust of the gates, the sluiceways, the chain paths and the gate recesses.

When the gates were closed and the water level at the back of the gates was greater than that in front of them considerable pressure was placed on the gates. This pressure was transmitted to the side walls which had to be strong enough to withstand it.

The provision of sluiceways was necessary for two reasons. Firstly they allowed water levels either side of the gates to be equalised so that the gates could be opened and secondly, they provided the means by which accumulations of silt could be cleared from the bottom of the gates and adjoining areas.