FRONT PROFILE OF DOCK WALLS. 109 



carried up simultaneously with the body of the wall. Excep- 

 tionally, they may be assumed, if carried well back, to increase 

 the grip on the bottom, and bond the wall with the backing to 

 some extent, or where the ground is very solid they may be of 

 great use in holding or keying the wall back to the backing, 

 and so admitting of a reduction in the thickness of the face- 

 work; but practically, under ordinary circumstances, they add 

 to the difficulty and cost of construction without affording equi- 

 valent advantages. In the majority of cases, the same mass of 

 material would be far more usefully employed in widening and 

 deepening the base, or in providing a substantial protecting toe, 

 or apron, in front. 



In putting in backing, it is of the first importance that there 

 should be no continuous sloping bed between the filling and the 

 natural ground, otherwise the whole wedge will have a tendency 

 to slide. In all cases, therefore, the natural ground should be 

 stepped and the filling deposited in layers inclined backwards 

 from the wall and well rammed; this treatment will tend to 

 increase the angle of repose. 



The front profile of a dock wall must be designed with some 

 regard to the convenience of the shipping that will use the dock. 

 An excessive batter is objectionable, inasmuch as the tendency 

 is to throw the side of a vessel further from the wall than is 

 convenient, and entails the use of cranes with longer jibs. 

 Convenient and ordinary batters are 1 in 8 or 1 in 12. 



A curved batter, particularly of short radius, is unsuitable 

 for tidal basins, especially where the rise and fall of tide is con- 

 siderable. The object of a curved batter is to increase the 

 stability of a wall by bringing the centre of gravity nearer the 

 back and somewhat lower; practically the ad vantages are proble- 

 matical, they are more difficult to construct and add to the cost. 



Where a curved batter is adopted, the radius is usually two 

 and a half to three times the height of the wall, and the centre 

 of the curve should be level with the top of the coping, by which 

 arrangement a portion of nearly perpendicular face is ensured 

 for ships lying alongside. 



Veiy long straight walls without a break often appear to 

 have a slight deviation outwards from the straight line ; this 

 apparent defect may be much minimized by giving to Avails of 

 over two or three hundred feet in length a very slight curve 

 inwards at the coping level. 



