2. Results . Four ootential configurations and loadinq conditions 

 were selected, the bendina moments per unit width, M ', calculated, and 

 then reinforced concrete and strucutral steel wall sections were desianed 

 to resist the applied bendina moment. Incut Darameters and calculated 

 wall thicknesses are contained in Table 16. The desinn assumed that full 

 loading could be apolied to either side of the cuttinq edge. The rein- 

 forced concrete desiqn utilized a working stress design and incorporated 

 76 mm (3 in.) of cover over the steel, the steel cutting edge design 

 also used a workinq stress design with efforts to minimize the wall 

 thickness, i.e., the section is not the most economical for resisting the 

 aoolied moment. The steel section was assumed composed of a row of H- 

 nile sections joined into a wall and stabilized by two steel sheets, 

 one on the inside flange, the other on the outside. The design thick- 

 nesses, t, for the cases analyzed were plotted and joined in Fiaure 42 

 to nrovide a thickness estimatinq curve for cutting edges. 



Please note these thicknesses, t, are based on a working stress 

 design while the Dassive resistances noted are ultimate loadings. There- 

 fore, a chanoe in technique for cutting edqe thickness desiqn may be 

 appropriate. 



Load Required to Penetrate Cuttinq Edges . 



1. Assumptions. The critical factor in dealinq with -cuttinq edqe 

 penetration is the soil shear strength assumed to be actinq. In the 

 treatment of cutting edge penetration, the tin of the cutting edge was 

 assumed to be penetrating in a bearing capacity failure mode with the 

 soil shear strength beinq mobilized being equal to the undistrubed shear 

 strenqth (see Figure 1). The walls of the cutting edge were assumed to 

 be slidino downward in partially remolded soil. The dearee of remolding 

 was assumed to be at least as great as the minimum value of sensitivity 

 auoted for that soil category (see Table 1 for sensitivities). The pene- 

 tration of the cutting edge was assumed to reduce the shear strength, s, 

 of a cateqory A soil by a factor of 2, a cateqory B soil by a factor of 

 3, and a category C soil by a factor of 2. The curves of soil side 

 friction, Sf, obtained by this techniaue are compared in Fiqures 43, 44, 

 and 45 with the recommended values, y (o + 2s ) , to be used for estima- 

 ting the soil side friction on driven steel piles (McCelland, 1974). 



2. Analysis . The cutting edge tips were assumed to be blunt. 

 Penetration of this blunt tip at the expected low emplacement velocities 

 is described by a conventional bearing capacity analysis. This approach 

 is conservative because every attempt will be made to streamline (sharpen' 

 the tips to reduce the tip resistance. However, unknown dynamic effects 

 may neqate any strength reductions due to streamlining, therefore, no 

 attemnt is made in the analysis to streamline the cutting edge tips. 



The walls of the cuttina edges were assumed not specifically 

 prepared, that is, smoothed or lubricated. 



85 



