MOHR'S CIRCLE OF STRESSES 



The Mohr circle of stresses is used to find the state of stress on any plane per- 

 pendicular to the plane of elemental volume of soil, AA'BB', shown in figure 2. Sign 

 conventions used are those commonly used in soil mechanics; normal stresses in compres- 

 sion are positive and counterclockwise shear stresses are positive. 



When the effective stresses, o a and t & , are plotted on Mohr's coordinates, the 

 obliquities of the various components are as shown in figure 9. Note that the stress 

 condition on plane A-A' is a function of depth. The state of stress (a , x ) will lie 

 on line DE if plane A-A' is above the water table, or on line EF if plane A-A' is below 

 the water table. The state of stress (a , t ) shown in figure 9 can be adapted to a 

 Mohr diagram, as shown in figure 10. 



Figure 9. — Stresses on plane A-A' shown on Mohr's coordinates. 



