Stability Analysis of Slope with Multiple Sliding Surfaces Based on Dynamic Strength-Reduction DDA Method

Table 2

Contact status table.

Contact switch	Contact condition	Contact force
Open-open	N > 0	No
Open-sliding	N < 0, |S| > |f|	Yes
Open-locked	N < 0, |S| < |f|	Yes
Sliding-open	N > 0	No
Sliding-sliding	N < 0, |S| > |f| or N < 0, ψ = −sgn f	Yes
Sliding-locked	N < 0, |S| < |f| or N < 0, ψ = sgn f	Yes
Locked-open	N > 0	No
Locked-sliding	N < 0, |S| > |f|	Yes
Locked-locked	N < 0, |S| < |f|	Yes

¹N is the normal contact force, S is the shear contact force, ψ is the direction of shear displacement, and f is the frictional force.