The cliff of the Mogao Grottoes has been subjected to serious weather erosion which can lead to landslides and falling rocks and poses a serious threat to the security of the caves and tourists that come to view them. The primary task of this essay is to investigate the source of falling stones, the process that loosens them, and to determine the exact area likely to be effected. The following conclusions have been drawn from geological surveys, field tests, field investigation, statistical analysis, and numerical simulation: 1. The Mogao Grottoes have two different kinds of stone falling, rolling stones that mainly happen in the Southern Area and peeled stones in the Northern Area that are stripped off the face of overhead cliffs. Rolling stones develop from the35—40 degree slope near the top of the cliff in the southern end of the caves, which roll down the slope after gradual loosening and movement. The horizontal distance the rolling rocks travel over the ledge is related to the mass and shape of the stones but generally falls within 2 to 5 meters away from the base of the cliff. This study is helpful for improving the preventative emergency warning system at the Mogao Grottoes, and provides some useful information for designing landslide risk monitoring and control measures.
