Tsao-Ling rockslides, involving mass movement of more than hundred million cubic meters, happened in the foothills region of Taiwan in 1862(pre-historical，earthquake), 1941(rain), 1942(rain), 1979(rain), and 1999（earthquake，M 7.3）. The Ching-Shui river was dammed in the 1862, 1941-1942, 1979, and 1999 events. Overtopping and breakaway of landslide dams were observed and recorded in 1951 and in 1979. The outcome of the dam-up lake of the 1999 event is being monitored. During the September 21st 1999 earthquake event, a rock mass of about 120-million cubic meters slid down the Tsao-Ling dip slope having a dip angle of 14 degree or so. Only 20%（about 25-million cubic meters）of the sliding mass dropped into the valley of the Ching-Shui river. Most of the sliding ma+H45ved behind the crest （called Crest Forever）of the dip-slope, flew over the Ching-Shui river and made moderate to soft landing on the remaining part of the old landslide dam. Seven of them were alive. 29 of them lost their lives. Some of the debris of their houses and a van （called Bou-Ma 747）can be seen in the center of Photography No.1 of this paper. They used the wireless telephone in the van to request help from outside Tsao-Ling village. Evidence of an air cushion under the sliding mass is given.
Soil liquefaction due to Chi-Chi earthquake was found at Taichung harbor and several counties along the coast in Taichung. As a result of this strong earthquake occurred at the middle of Taiwan and the duration was long enough, the counties, Wufeng and Taiping, next to the western mountain areas also had serious damages due to soil liquefaction. Locations of soil liquefaction and corresponding damages in these two counties are investigated and described in this paper. There are several phenomena associated with soil liquefaction can be observed, they are sand blows, settlement and inclination of ground or buildings, lateral movement and spreading, and flow failure. The major places of sand blows are found to locate close to or beside the rivers, especially the sedimentation side of a river. The possible depths of liquefaction and soil properties are analyzed using collected boring log data and results of grain size distribution of the sand blow.
The Chichi earthquake, with a magnitude of (Ritcher Scale) 7.3, struck central Taiwan in the early morning of 21 September, 1999 at 1:47 am, and caused wide damage not only in the central region but as far as the whole Taiwan island. More than 2,300 people died in this big disaster. The Yuan-Lin area in ChangHua County suffered extensive damage including settlement and inclination of buildings and roads due to liquefaction. This article presents the results of field reconnaissance of the liquefaction affliction. Several locations, including obvious phenomenon of sand boils on the ground and inclination or settlement of the roads and buildings due to liquefaction were photographed and marked on the map. Nonetheless, without obvious sand boils on the ground do not mean that there is no liquefaction happened underground. In order to determine possible areas where liquefaction could take place, extensive evaluation must be undertaken. The records of liquefaction affliction presented in this article will provide correlative information for further assessment and analyses of the liquefaction problem, and thus to assist in determining liquefaction potential in the entire Yuan-Lin area.
The Chi-Chi Earthquake, which is the most damaging one on the Western Island of Taiwan in past hundred years, not only caused disastrous torrential changes but also induced soil liquefaction in Central Taiwan, which in itself is also very scarce. This article serves as a liquefaction disaster report on the three reclaimed lands, My-Lio Industrial Park, Chun-Pin Industrial Park, and TaiChung Harbor. Preliminary studies on the causes are also included to serve for future references for the development of reclaimed lands.
This paper presents the results of reconnaissance and preliminary analyses about soil liquefactions occurred during the Chi-Chi earthquake. This study focused on: (1)ground motion characteristics; (2)soil characteristics of liquefied sites; (3)liquefied phenomena and structure damages; (4)verification for critical cyclic strength curve of soil liquefaction. Results show that the liquefied soils have rather high fines content and lateral spreadings are very common in this earthquake. Data obtained can be used to verify the cyclic strength curve commonly used in engineering practices.
A severe disaster due to 921 earthquake occurred in the north wharf of Taichung harbor. The damages of wharf has been investigated and studied. This paper provide the detailed investigations which will be useful for the maintenance or construction for harbor engineering. After site investigation, it is found that the damages occurred in the north wharf include sand boiling, rupture, ground settlement, heaving and tilting of structures. The main reasons which caused the damages are the large intensity of shaking, soil liquefaction and leakage of sandfills behind the caissons.
This paper is aimed to evaluate the investigation results of the Chi-Chi earthquake induced foundation failures and to propose some possible remedial measures for the liquefaction resulted foundation failure. Basically, most of the earthquake induced damages were on the upper structures. The damages to the foundation were minor. Totally, 19 towns and cities were investigated and 457 foundation failure cases were reported. Among them, 267 cases (58%) were related to the interface failure between upper structure and foundation; 123 cases (27%) were subjected to the fault induced surface up-heave; and 67 cases (15%) were caused by the subsoil liquefaction. For areas far from the epicenter but with the fault passing through, the foundation failures were mainly caused by the surface up-heave and were concentrated along the fault. For area closer to the epicenter, not only the fault induced surface up-heave but also the earthquake force are the major causes of foundation failure. As a result, the distribution of the foundation failure spread wider. Since the soil liquefaction was only occurred in certain areas and the scale was small, the liquefaction induced foundation failure was not significant. To improve the ground condition against liquefaction for the areas had been attacked or will possibly be attacked by the liquefaction, both the grouting method and the underpinning method are recommended here considering their workability and effectiveness. But the long term durability of grouting material and the resistance against the lateral load of underpinning piles should be carefully evaluated.
This paper reports failure of gravity walls, masonry walls and reinforced-earth walls related to the 1999 Chi-Chi earthquake. After the earthquake, sliding and overturning failure of retaining structures were observed. The failures were most probably induced by the dynamic earth-pressure and lateral spreading of the uphill slope. A gravity wall built right above the Chelungpu fault was severely damaged by the vertical and horizontal movements of the fault. It is suggested not to build any retaining structure on top of an active fault.
The Chi-Chi earthquake occcurred at September 21 early morning (1:47AM) in 1999. The epienter was located at 12.5 Km far from the west of Sun-Moon Lake, Chi-Chi, Nantou county . It has been recognized as a serious disaster caused by Chi-Chi earthquake. The Damges of public consturction, agricultural facilities, humman activities supporting networks and transportation systems have been identfied and investigated by using aerophotography and satellite image processing technology. 2365 landslide spots have been identified by the aerophotography technology. The stability of dam-forming landslide located at Nantou county proved to be critical and important in the disaster area. The volume of impoundment was estimated to be 35*106m3 in total area of 698 ha. .In fact, the most common initiation mechanisms for dam-forming landslide are excessive rainfall, snow melt and earthquake. However, most landslide dams are remarkably short lived. The landslide daming of rivers in Nantou county has proved to be a significant hazard in the near future . The main purpose of this premier investigations is to collect all informations which can give a reference for the stabliization of landslide and landslide dam afer Chi-Chi earthquake.
The Chi-Chi earthquake was the most violent one among those earthquakes occurred on land during this century. Many large dams and tunnels located within 50 km circle of the epicenter were shaked by violent ground tremble. After careful inspection of those structures, no significant damages except Shikang dam whose vertical alignment was abruptly changed by differential ground uplifts. As for tunnels, only the outlet tunnel of Shikang dam collapsed due to ground offset. From overall review, current geotechnique for dams in Taiwan have passed a severe challenge during the earthquake. Incidentally, earthquake resistance characteristics of tunnel has been proven in many tunnels during this earthquake.
Based on the case histories of earthquake performance of earth dam collected from Taiwan and abroad, a preliminary review on the seismic performance of earth dam in Taiwan and the reliability of the seismic safety assessment methodology adopted was made. The effects of 921 Chi-chi earthquake on earth dams show that well-constructed earth dam can resist strong shaking with as high as 0.6g without severe damage. The methodology of seismic safety assessment adopted can estimate the dynamic response and the final settlement of dambody reasonably well.