The equation to predict shear strength of claystone backfill will be consider from the effect of increase moisture and deterioration of claystone.
Study of deterioration and increase of moisture effected to size distribution of backfill and strength of claystone that use as backfill materials.
The changing of size distribution and strength of claystone is the importance factor that will be effected to shear strength when consider from Barton equation.
From this correlation, we can write the equation to predict shear strength of claystone backfill when they changed because deterioration and increase of moisture.
When we can predict the decrease of shear strength, we can use this shear strength parameter to analyze stability of slope and can predict factor safety of claystone backfill slope.