Collapse types of the slopes along the highway from Yingxiu to Wolong after Wenchuan earthquake determined using stereographic projection method

After the earthquake,there grows structural surfaces in highway rocky slope,they easily become unstable to collapse.Choose the typical structural surfaces from many ones as structural surfaces controlling rockfall,then analyze the engineering geological conditions of structural surface in the slope,selecting principles of structural surface controlling rockfall are obtained.Considering the space position between structural surface controlling rockfall and free face of the slope,using stereographic projection method,emphatically analyze the space relation between a group or two structural surfaces controlling collapse and free face of the slope.Post-earthquake collapses happened to highway slope are divided into three collapse types,including sliding type,toppling type and falling type.Combined with factors including slope lithology,slope shape,slope gradient and slope height,the criterion of three collapse types for post-earthquake highway slope are obtained.Collapses types from the given criterion using the typical collapses growing in highway from Yingxiu to Wolong are in accord with the actual condition.