Based on the shallow translational slip model of soil slopes under seepage parallel to slope surface

the rectangular frame protection unit is taken as a research object

the relationship between soil skeleton and the interaction and soil shear strength of nonlinear characteristicsthe are analyzed under the lower stress level. It is proposed that the three failure modes including the direct shear sliding mode and retaining passive failure mode which happened in rectangular frames

and their threshold lsp reflecting vertical distance. The factor of safety for the shallow stability of soil slopes protected by rectangular frames under the influence of seepage parallel to slope surface is established; and the checking method of protection engineering which aimed the factor of safety and frame structures strength is also presented. The analytical results show that the threshold lsp is determined by frame structure thickness

h

and increases with increasing h. Among the three modes under the influence of vertical distance

lv

the lv under the modes Ⅱcomparing to mode Ⅰ

have more significant impact on the factor of safety

and if failure mode was determined falsely will induce dangerous result due to highly estimating resistance force from frames. In the condition of satisfying the factor of safety for shallow stability of soil slopes and the frames structure strength

the type of horizontal window with depth cross comparing to vertical window with planar cross can save more masonry amount.