KEYING UP
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out to a flat angle. Where sea exposure is considerable, the slope of the wall should approximate to that of the sea beaches in the vicinity. For estuarial embankments it is usual for the front slope to be at an inclination of 1 in 2, and the back of the wall 11 to 1. In the reclamation bank on the south side of the Ribble, the slopes of the upper half were 2 to 1, and of the lower half 5 to 1. In Lincolnshire and on the Wash the front slope is generally 5 to 1. Frontages to rivers or creeks where exposure is not extreme will stand quite well at 2 to 1, but where heavy sea-bursts are anticipated it is better to reduce the slope to 3, 4, or 5 to 1. The usual width of the top of the bank is 3 feet, sometimes 4 feet. In positions of exposure it is often necessary to pile the front edge of the wall by means of short piling, as described above. It used to be common practice to drive piling in successive rows and fill the space between with stone pitching; these spaces were called “rooms”. This practice is, however, not to be commended. It is difficult to secure the consolidation of the stone pitching up to a line of pile stumps, and the timber when soaked in water changes its volume and is subject to decay. The consequence is that the stone-work becomes loosened and a heavy run of sea or tide may quickly dislodge a portion of it, when the stone pitching lying above such breach slips, and the result is a dangerous cavity in the wall, which is exposed down to the clay. The usual practice in southern England is to pitch the surface of the clay with chalk, and a depth of 8 inches is a common thickness. Above the chalk stone pitching, generally 12 inches thick, is used; ragstone is mainly used in the south. Rendering this stone-work rigid is termed “keying up” the bank. Most exposed sea-walling requires keying up once a year, and this consists of adjustment and driving home fresh stone-work. It frequently happens that a stone-dressed surface is not sufficiently stable to stand the heavy blows of the sea, and in localities where the run of the water is extreme such stone-work is sometimes grouted in cement, finished with a smooth surface. This practice has the disadvantage that in heavy gales the seas run up the bank and the spray is carried over the land in rear by the wind.