EXAMPLES OF WALL SECTIONS. 



155 



the hearting was then filled in, and the whole finished with a 

 granite coping and causeway. 



Spezzia. At the Italian Naval Station of Spezzia, 1 experi- 

 ments made in 1865 to ascertain the true nature of the ground, 

 which was composed of silt, sand, and clay in varying proportions, 

 demonstrated the necessity of building the dock walls of unusual 

 thickness to prevent them slipping forward by pressure from 

 behind, which, experience had proved, would be exceptionally 

 severe. 



Two sections were adopted, viz. Fig. 136, where the bottom 

 was comparatively solid, and Fig. 137, on soft ground. 



The walls were 41 feet high throughout. In the lighter 

 section, with a base of 23 feet (Fig. 136), there were no open 



f 9 



SCALE 



.0 20 



so FEET 



FIG. 136. 



FIG. 137. 



spaces in the body of the work ; whilst in the heavier section, 

 with a base of 29 feet 6 inches (Fig. 137), pockets or wells were 

 formed 15 feet long with division walls 5 feet thick between 

 them. 



In constructing the interior dock walls, the necessary ex- 

 cavations were first made to 13 feet below the sea level, leaving 

 the earth at the natural slope ; then having to lay the founda- 

 tions at 36 feet under water level, and to cut through a muddy 

 stratum, the work was done in lengths or sections, the vertical 

 sides of the trench being sustained by boarding and heavy 

 timbering. The sections varied from 23 feet to 33 feet in 

 1 M.P.I.C.E., yol. lv. pp. 103, 104, 105. 



