There are three phases ot wall failure, viz: overturning, crushing and sliding. The first two have ben 

 properly cared for in the designs shown. The third depends more or lesson the nature of the toil which 

 is taken for the foundation. A wall built on solid rock does not necessarily have to be keyed, but the 

 surface of the rock should be roughened. In all other soils a key is absolutely necessary to keep the wall 

 from sliding and throwing the wall out of alignment. The key is shown on all designs, Plates I, II, III, 

 and IV. The key is that small portion of the wall which projects downward from the base at about its center. 



Proportion 1: 2: 4. 



If it is desired to guard strongly against seepage of water through cracks which may result from temperature 

 changes, expansion joints should be provided at intervals of thirty feet which extend from the foundation 

 bed through the coping. Water may be prevented from seeping through these joints by forming a rect- 

 angular vertical recess in the wall as it is built up, which is filled and well rammed with plastic clay. 

 Authorities differ on the subject of expansion joints. In many instances cases may be cited where expansion 

 joints have been left out, and the work found perfectly satisfactory. 



I he Key . 



Sufficient steel has been allowed in the designs hereinafter submitted to take care of temperature sir 

 according to theoretical and common practice. It should be remembered that there is a b?g distinction be- 

 tween surface hair cracks and deep cracks permitting seepage. 



A concrete mixture so proportioned as to give the maximum density has been demonstrated to be satis- 

 factorily waterproof. If it is deemed advisable, however, any good waterproofing compound may be added. 



Many methods of finishing concrete surfaces are in vogue. Some are as follows: 



Cement washing or grouting 



Rubbing up 

 Tooling 

 Sand Blasting 



Plastering 



Concrete : 



Expansion 

 Joint*: 



Water- 

 proofing : 



Surface 



I inish: 



in 



