EXAMPLES OF WALL SECTIONS. 123 



is 33 feet 7 inches, the width at the base 19 feet, and at the 

 top 8 feet 2 inches. This difference of thickness is obtained 

 on the outer face by a batter of 1 in 10, followed by a curved 

 face to the foot to a radius of 26 feet, and at the back by offsets 

 of 14 J inches wide. 



Fig. 83 shows the wall on the west side of the floating basin, 

 modified to include a culvert at the rear. The total width 

 of the base in this case is 29 feet 6 inches, resting on a concrete 

 foundation 31 feet 6 inches wide enclosed with close sheet-piling, 

 as in the case of Fig. 82. 



Southampton Deep-water Tidal Dock. 1 The trenches for these 

 walls were excavated 100 feet wide at the top, battered down 

 at a slope of 1J to 1 in the mud by barrow roads to a depth 

 of 18 feet, and were then continued at a slope of 1 to 1 by 

 horse roads to a depth of 34 feet, when timbering was resorted 

 to for supporting the sides of the excavation; the material 

 being lifted by the aid of steam-cranes and skips. 



The borings along the east wall (Fig. 15) indicated the 

 worst soil; 17 feet in depth was found to be mud with 14 feet 

 of peat under it overlying gravel. On the line of the north- 

 east wall (Fig. 15), there was 10 feet of mud in some places, and 

 in others 5 to 6 feet; then followed gravel and considerable 

 depth of clay on which the foundation of the wall was for the 

 most part laid. On the line of the west and south-west walls 

 (Fig. 15) there was 10 to 12 feet of mud with gravel and clay 

 underneath, on which the wall was founded. At the north-east 

 corner of the dock it was deemed necessary, owing to the sandy 

 nature of the strata, to put in piles, which were driven to a 

 depth of 12 feet, 2 to 3 feet being left above the surface to 

 form a key with the foundation as a precaution against the wall 

 slipping forward. It was, however, found extremely difficult to 

 drive these piles, and the attempt was ultimately abandoned 

 and the sand removed instead. 



The walls were constructed entirely of concrete to the general 

 sections shown by Figs. 90, 91 ; the proportions being 8 parts of 

 clean gravel and sand to 1 part of Portland cement for the body 

 of the wall, with a facing from 26 feet below coping upwards, 

 and 12 inches thick mixed in the proportions of 5 to 1. 



The concrete was laid in layers from 2 to 3 feet thick, and 

 was allowed two clear days to set before the casing was 



1 Engineering, vol. 1. p. 309. 



