Appendix B 

 ■EXCAVATION ANALYSIS FOR TRENCHING 



CHAIN-DRIVEN BUCKET TRENCHER 



In order to calculate the forces required to excavate a trench, some 

 trencher configuration must be selected. From Reference 47 one selects 



chain speed = 9.2 ft /sec 



bucket distribution = 1 bucket/ft 



The other parameters required are as follows (Figure B-1): 



Depth of cut, D = 3 ft 



Width of cut, w = 4 in. 



Speed of advance, v = 1.69 ft/sec 



2 

 Soil shear strength, S = 4 lb/in. 



xSXxxvT 



xx><?<?<c^ 



Figure B-1. Trench configuration. 



The total force required to cut the soil is the sum of the soil bearing 

 resistance and the soil shearing resistance (friction) [38] or 



TOT 



= F, + F^ = A^ N S 

 b f f c i 



A S 

 s I 



where F, 



TOT 

 F, 



= total cutting force required 



= soil bearing resistance 



= soil shearing resistance (friction) 



frontal area 

 = factor ^ 3 

 = shear area 



62 



R 



