By employing the same assumption used in the Sarma method

that is

the shear strengths along the interface between slices are mobilized to the same degree as that along the slip surface

the lateral thrusts of oblique slices are decomposed into two components related to friction and cohesion respectively.According to the force equilibrium of a slice a more concise recursive equation is derived in terms of the safety factor.The Newton method is employed for computing the safety factor in order for fast convergence.Relevant derivatives needed in the computation are derived that are in recursive form and of analytical nature.Meanwhile

by using the present recursive equation an explicit expression of critical seismic coefficient is obtained which is equivalent to the original equation of the Sarma method

but is in simpler form and easy to apply.Example studies demonstrate that the modified algorithm of the Sarma method converges rapidly and only 3-5 iterations are needed for achieving the precision required by practical engineering.The results of computations are in close agreement with both the classic solution of the Sarma method and the theoretical solution based on the mechanics of plasticity.