Discussion on the ideas of vegetation restoration design of highway cutting slope in semiarid mountain：Take Beijing-Chengde Highway (the third period) of Beijing for instance

In this paper,the section of Beijing-Chengde Highway in Beijing was taken for instance. Six species of arbor,six species of shrub,six species of herb and two species of liana were chosen,and four vegetation restoration techniques were used to restore the slope ecology, i. e. the external-soil spray seeding, the thick layer base material spraying，the cotton net plant biological bag, and the plain stage of slope. In this paper,some questions need to be noticed,which are regarding vegetation restoration design of highway slope in semiarid mountain,were also discussed.