Abstract：Due to the fact that either there still exists an unbroken part on bedding-plane and/or flanks in landslide at the critical failure stage，or there appears a narrow and limited sliding path in front of sliding mass after the onset of landslide，a horizontal soil arching is developed across the narrow limits between the flanks of landslide，leading to restriction of deformation or braking of movement. In landslide，soil arch acts as a locked segment that gives direct support to soils over crown and prevents them from slipping downward，resulting in compacting and swelling of soil mass here. On the other hand，soil arch transfers the majority of vertical load above crown onto the arch abutment (double flanks in landslide) through the crown，which makes the abutment become the place of stress concentration. Once a rise of pore pressure by compaction of soils reduces shear strength on plane between arch and arch abutment to a low one so that one of the abutments fails keeping equilibrium，the crown would buckle completely giving rise to whole sliding of the landslide. The stress trajectories obtained from model test indicate that an arched region is composed of two different stress arches，i. e.，the maximum principal stress arch protruding upward and the minor principal stress arch dipping downward，and the computation model is proposed accordingly. It is supposed that the soil is in a state of plastic equilibrium and Mohr-Coulomb yield criterion is satisfied，the vertical load acting on the support arch is estimated by considering forces of self-weight of soils，shearing strength on bedding-plane，resistances at flanks，and stress redistribution caused by the soil arching effect. Consequently，the stability criterion of landslide is deduced and a practical case is analyzed，from which the presented study result is proved to be effective in the quantitative evaluation of stability of this kind of landslide.
