Final Report
1994-1998 IDNDR Project

C-2FLandslie Hazard Assessment of Lishan Landslide,
Xian,China

The Imperial Resort Palace, known as the Huaqing Palace, Xian, Shaanxi Province, China(Fig.1), had a famous history in the ancient age of the Tang dynasty(618-907 A.D.), in which the Empress Yang-Que-Fe enjoyed the hot spring at the palace. There are no volcanoes near Xian, however, many active faults can be found near the Huaqing Palace. The hot spring continues to produce hot water and the Huaqing Palace is nowadays one of the most popular tourist resorts in China. Every year about three million tourists visit this resort. The palace is located at the toe of a steep fault cliff, called Lishan mountain("shan" means mountain), as shown in Figs.1 and 2. Beginning in 1985, slope deformation has become obvious; indications of movement are given by small slope failures at the foot of the slope, subsidence at the head of the cliff, and many cracks in the slope and structures. The Xian municipal govemment established the Lishan Landslide Prevention Observatory(LLPO)in 1986 to start monitoring of the Lishan slope for protection management of the cultural heritage and tourists. In 1991, This joint research project between DPRl and LLPO started with purposes of(1)to clarify whether this deformation is landslide or fault movement, (2)to assess catastrophic landslide hazard of the Lishan slope.

Fig.1 Location of Lishan,Xian,Shaanxi Province,China and photo of Huaqing Palace. Flg.2 Plan map of Lishan landslide and Huaqing Palace.
Fig.3 Record of the Short-span extensometer(EX.1 in Fig.2)during 1992-1996. Fig.5 A record of the Long-span extensometer in 1996 which implies large block movement induced by heavy rainfull.


A Short-span extensometer(10 m, Ex.1 in Fig.2)monitoring record of over 6 years shows that the slope movement corresponds to precipitation(Fig.3). This implies that the slope movement is not caused by the fault activity, but due to landslide movement. Total Station monitoring reveals that part of the slope is dragged along with wide area ground subsidence including the Huaqing Palece which is mainly caused bay hot water pumpingup Monitoring by GPS survey of stations widely distributed around the Lishan slope detected no obvious displacement.

Thirteen series of long span extensometers(Fig.4)of 40-60 m span for each, were instaued along A-and B-Lines(two red lines in Fig.2). The poles on which the pulleys were positioned, are made of concrete and are 14 meters high.

Extensometers and super-invar wires are installed inside metal boxes and pipes to prevent thievery. The monitoring records reveals(1)Examined with field investigation, the Lishan landslide consists ofthree blocks, (2)the Block 1 Which is adjacent to the Huaqing Palace is most active because both extension at the head and contraction at the foot of the block of about lO mm were observed corresponding to precipitation(Fig.5). Taking into consideration with fresh fault gouge of low angle found inside invesigation tunnel on the slope, there is no doubt about the deep potential landslide on the fault gouge which is now at the initial creeping stage. Landslide simulation tests using ring shear apparatuses of alluvial deposits taken from inside the Huaqing Palace Were carried out. Obtained data were used for landslide runout simulation by computer based on geotechnical model for each block. These simulation results suggest that this huge landslide would result in catastrophic destruction of central part of Lintong county where about 700 thousands people are living. These joint research reports gave enough reason for starting prevention works by Chinese govemment of about three miuion USD(Fig.6).

It is important to note that enough investigation and observation can make reliable risk assessment of largescale landslides and prevention works based on the assessment is possible. This joint research project will continue further as a UNESCO-IGCP project lnternational Geological Correlation Program(IGCP)No.425 "Landslide Hazard Assessment and Mitigation for Cultural Heritage Sites and Other Locations of High Societal Value" for further study on real-time monitoring, waming, and prevention work suitable for Chinese situations. For more information about the IGCP425 can be accessed at
http://landslide.dpri.kyoto-u.ac.jp/igcp/

Fig.4 Long-span extensometer install on the Lishin slope. Fig.6 Landslide prevention Works under construction.

Selected Bibliography
Sassa,K.(editor). 1994. Proceedings of Special Session, Prediction of Landslides in Lishan, China, Intenational Workshop on Prediction of Rapid Landslide Motion, Kyoto,251 pages.
Sassa,K. 1994. Prediction of Landslide Motion in Lishan(Huaqing Palace), Xian, China, Landslide News, No.8,pp.22-25.
Fukuoka,H, K,Sassa, Q.J.Yang, and B.E.Song. 1997. Extensometer Monitoring in the Lishan Landslide, Xian, China. Landslide News, No.10,pp.23-25.