| The ancient city of Jiaohe, as one of the first batches of state emphasis cultural relic unit, is the best representation of earth site in China and abroad. It has been destroyed seriously by natural effects and people. And the cliff collapse seriously due to developping many joint and unloading fissures, studies for destroyed mechanism is necessary. Based on the studies which other scholar have done, this thesis studied the destroyed mechanism deepply, and used numerical software to simulate the process how cliff destroied.Summarize the datas from other scholar have done and the fieldwork, this thesis summarized the geological condition of the ancient city of Jiaohe: It sit on the west of the Turpan Basin, the stratum belongs to lacustrine sediments, the climate belongs to the typical continental-warm temperature-drought-desert climate.Several typical area are picked out considering the destroyed conditions, including area 17, area 26, area30 and area 41. The situation of how unloading fissures and stratum distributing is researched detailedly by using Electronic Total Station and other geodesic instruments. All the datas collected are used for analysing destroyed mechanism of Jianhe cliff.Many experimentation has done in laboratory, including Scanning Electron Microscopic(SEM), common physical and mechanical experimet. The results show that the cliff mass is made up of clay and sand. The property physical and mechanical is very strong in dry condition. It has anisotropism, the property in plumb direction is better than in aclinic direction. This thesis use the software FLAC3D which based on Finite-difference theory to simulate how cliff destroyed in each area. Including three conditions: no unloading fissures, the unloading fissures developed and the cliff has been undercutted. The results show that when the unloading fissures developed and the cliff has been undercutted, collapse will happened in two mode: topple or slide.
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