DEFORMATION MONITORING &|ANALYSIS OF ANCIENT LANDSLIDE AT ZHANGMU PORT IN TIBET

A group of huge ancient landslides locates at Zhangmu port to the south of Himalayas. The slope terrain of the landslides is steep. The regional tectonic movement is strong. Seismic activity is frequent. Rainfall is very abundant. The lower of stratum forming the landslides is biotite plagiogneiss schist of Sinian period. The upper is eluvial deposits,colluvial deposits and deluvial materials of Quaternary period. In recent years,some of the ancient landslides moves acutely as a result of rapid town construction and development. The ground movement has caused damage of many town buildings. It is estimated that properties of about 8 hundred million RMB and 8000 local people are being threatened by the landslides. The systematic deformation characters and patterns of the landslides are examined with the superficial crack monitoring,superficial displacement monitoring and deep borehole displacement monitoring. The results of the monitoring indicate that two ancient landslides may be stable. Rainfall and human activities triggered the revival of Xiaofangdui landslide. This Xiaofangdui landslide is at the stage of creep and extrusion. Its landslide deformation has a slowly rising tendency．