Abstract：A study is undertaken on mechanical stability of man-made mixture sprayed on slope surface，i.e.，replace with out-soil，in ecological slope engineering. It is found that the failure mode of replace with out-soil is a translated sliding surface parallel to original slope surface from indoor simulation tests. Based on this failure model，stability analysis of replace with out-soil is carried out；and then a general equation for stability thickness of replace with out-soil under earthquake and seepage is given. Stability design charts for replace with out-soil are obtained after discussion on parameters of the equation. Indoor simulation tests testify that the charts are effective. Using the charts，the stability thickness of replace with out-soil can be designed using given design safety factor，vice versa，safety factor of replace with out-soil in constructed ecological slope can be calculated.
