EXAMPLES OF RETAINING WALLS. 



237 



TABLE V. 

 WEIGHT, SPECIFIC GRAVITY AND CRUSHING STRENGTH OF MASONRY. 



TABLE VI. 

 WEIGHT OF DIFFERENT MATERIALS. 



For specifications for concrete, plain and reinforced, see Chapter VI. 



EXAMPLES OF RETAINING WALLS. Details of six masonry retaining walls with a 

 gravity section are given in Fig. 10. These retaining walls represent the best practice. Details 

 of four reinforced concrete retaining walls are given in Fig. n. For additional examples see 

 the author's "The Design of Walls, Bins and Grain Elevators." 



The contents of standard concrete retaining walls, as designed by the Illinois Central Rail- 

 road, are given in Fig. 12. 



Concrete Retaining Walls. Methods of Constructing Forms. Forms for a retaining wall 

 may be built in sections, or may be built up each time they are used. The former method is 

 much the cheaper, especially for plain concrete walls where the sections between expansion joints 

 are of equal length. The forms used on the C. B. & Q. R. R. walls shown in Fig. 13 are shown 

 in Fig. 14. The studs, coping and bottom forms for the face, and the back forming are sectional, 

 while ordinary sheeting is used between the coping and bottom forms. No attempt was made 

 to use sectional forms on the face of the wall, because the sections soon become badly warped, 

 making a rough wall. The concrete had a tendency to lift the forms and they were tied to bars 

 imbedded in the footings as shown. The sectional forms were 12 ft. o in. long, while the studs 

 were spaced 3 ft. o in. center to center. 



The forms for the Illinois Central R. R. retaining wall shown in Fig. 10 are shown in Fig. 15. 

 The forms were built in sections 54 ft. long. The forms were cross-braced by J in. rods spaced 

 7 ft. 8J in. center to center as shown. When the forms were taken down the ends of these rods 

 were unscrewed, the main portion of the rod being left in the wall. The forms were made of 

 2 in. plank surfaced on the inside. 



The forms used by the Chicago and Northwestern Ry. on track elevation in Chicago are 

 shown in Fig. 16. The forms were built in sections 35 ft. long. The 2 in. X 8 in. braces were 

 used to hold the sides of the forms apart and were removed as the concrete was put in place. The 

 2 in. pipe used to cover the rod bracing was old boiler flues and rejected pipe. 



Ingredients in Concrete. The proportions of concrete materials should be stated in terms 

 of the volume of the cement. The volume of one barrel or four bags of cement is taken as 3.8 

 cu. ft., and the sand and aggregate are measured loose. Concrete mixed one part cement, 2 parts 

 sand, and 4 parts stone is commonly called 1:2:4 concrete. The proportions should be such 



