The fast Lagrangian difference method of continua is used to analyze the effect of excavation on the safety factor of slop in slide-resistant piles construction.Strength reduction technique by setting a failure criterion——the divergence of maximum unbalance force——is also employed to study this three-dimensional problem.Comparisons are made of the computed safety factors associated with different construction sequences and the most reasonable construction sequences are resulted

which is found to cause little disturbance on the slope stability.However

casual excavation for pile construction may cause slope instability with small displacements

and the slope would collapse abruptly without obvious precursors.Moreover

it is necessary to analyze the safety factor decrease caused by construction especially for slopes in critical states.