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| SURFACE RUPTURE AND GROUND DEFORMATION ASSOCIATED WITH THE CHI-CHI, TAIWAN EARTHQUAKE |
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| 李錫堤 康耿豪 鄭錦桐 廖啟雯 |
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| 地震斷層、地表破裂、地盤變形 |
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| 發生於台灣中西部地區的921集集大地震，除了提供了世界上有史以來最完整的地震記錄，並為本世紀發生在陸地上逆衝斷層活動中的最大者，亦提供了研究低角度逆衝斷層破裂及地盤變形現象的絕佳機會。此次地震斷層破裂長達近百公里，最大水平位移量達約十公尺及最大垂直位移量達約八公尺，地盤變形現象集中在斷層上盤，其變形範圍少者數公尺，多則數十公尺寬；少數特例更達數百公尺到超過一公里之情形。在變形帶內，地盤拱彎、傾斜，產生分支斷層及張裂縫，有時更有背衝斷層出現。車籠埔斷層沿線的地盤變形現象大致可分為九類，包括：(1)純逆衝變形，(2)單斜褶皺變形，(3) 純拱彎變形，(4) 逆衝及拱彎變形，(5) 逆衝拱彎及地塹變形，(6)拱彎及正斷層變形，(7)逆衝及背扭褶變形，(8) 逆衝及背衝斷層變形，及(9)逆衝及多張裂帶變形等。一般而言，純逆衝及純拱彎的變形現象較為單純，變形帶也較窄；逆衝及拱彎變形次之；餘各類則屬較複雜之變形，變形帶也較寬。無論斷層變形帶的寬窄，斷層錯動是對建築及結構物最大的破壞，所以防震設計首要避開斷層錯動面。美國加州自西元1972年後，開始有斷層帶限建之規定。921集集大地震之後，我國也開始有類似之思考。然而，對於複雜的斷層，到底應如何劃設禁限建帶，則須謹慎考量。原則上，一般建築及結構物最好能適當地避開斷層錯動帶，但對於安全性要求極高的結構物，例如：核能電廠及大型水壩等，則應有更特別之考量。 |
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| The 1999 Chi-Chi, Taiwan earthquake is the largest known onshore thrust-faulting event that has occurred in the 20th century. It provides an excellent opportunity to characterize the surface rupture and ground deformation associated with thrust faulting. The surface faulting along the Chelungpu fault produced by the earthquake extends north-south about 96 km, and has a maximum horizontal slip of about 10 m and a maximum scarp height about 8 m. Ground deformation occurred predominant on the hangingwall, ranged in width from several meters to several tens of meter. In a few cases, the deformation zone was several hundred meters wide, and it was even wider in Tsuolan area. In the deformation zone, there are secondary faults, branch faults, open cracks and/or tilted ground, which damaged existing buildings and structures. Along the length of the Chelungpu fault rupture, hangingwall deformation may be classified into 9 different styles. This includes: (1) Simple thrusting, (2) Monoclinal folding, (3) Simple warping, (4) Thrusting and warping, (5) Thrusting, warping and graben formation, (6) Warping and normal faulting, (7) Thrusting and back-kinking, (8) Thrusting and backthrusting, and (9) Thrusting with multiple zones of open crack. Simple thrusting and monoclinal folding generally represent narrower deformation; whereas more complex zones of deformation tend to be wider. Fault rupture is the direct reason to cause serious damage to engineering structures; the deformation zone away from fault tip is not so critical to common buildings and structures. One method of mitigating hazard from earthquake surface rupture, currently being used in California, is to develop setback zones along fault traces in order to restrict the location of structures for human occupancy across the trace of an active fault. After the Chi-Chi earthquake, the Taiwan Government is also developing a similar rule. However, for complicated faulting like the Chelungpu, it is not easy to draw a simple setback zone to avoid all possible damage from the next earthquake. However, the most important point for a common building or structure is to avoid it from across fault crush zone. But, for a critical facility, like a nuclear power plant or a high dam, sitting and construction on the hangingwall deformation zone should be avoided. |
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| DISASTERS, CHARACTERISTICS, AND CASE ANALYSIS OF SLOPE FAILURES CAUSED BY CHI-CHI EARTHQUAKE |
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| 洪如江 林美聆 陳天健 王國隆 |
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| 921集集大地震、坡地災害、坡地破壞特性、個案分析、順向坡滑動 |
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| 921集集大地震對中部地區造成嚴重的坡地破壞，廖軒吾（2000），根據該地震前後的衛星（Spot）影像、航空照片、以及現場核對，得知該地震一共誘發了9272個面積大於625平方公尺的山崩，總面積約達127.8平方公里。 林美聆、廖洪鈞與翁作新（Lin, Liao and Ueng, 1999）之研究結果顯示：幾乎所有的坡地破壞都發生於車籠埔斷層之右（東）方。國家地震工程研究中心所支持的大地工程震災現地調查，確實掌握了中部山區436處坡地破壞的資料。 本文研究針對這436處坡地破壞的特性作進一步分析，發現本次地震所導致的坡地破壞大都屬於中至小型規模的淺層岩屑滑崩，且其坡度大都較為陡峭，在地震所引致的坡地破壞中，地表運動可歸納為導致坡地破壞的最顯著因素。本文對四大坡地災害（草嶺大崩山、九份二山順向坡滑動、中部橫貫公路谷關德基段之全面崩潰、與九九峰之禿頭）加以討論。 草嶺及九份二山的反算及穩定性分析也於本文之中一併探討。 |
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| The Chi-Chi earthquake has caused extensive slope failures in central Taiwan. Liao (2000) pointed out that Chi-Chi earthquake caused about ten thousand landslides to the area, each of which is larger than 625 square meters and that the total area of the landslides exceeds a hundred square kilometers. In their paper on the geotechnical hazard caused by Chi-Chi Earthquake, Lin, Liao, and Ueng (1999) showed that almost all of the slope failure sites are located to the right（east）of Che-Lung-Pu fault. Based on 436 landslides investigated by professors and experts in the field of Geotechnical Engineering, the characteristics of slope failure for these landslides are analyzed. The analysis reveals that most of the landslides induced by the earthquake were small to medium size and were typically shallow debris slides of steep slopes. For the earthquake-induced landslides, ground motion is thought to be the most significant factor.Among all the landslides triggered by Chi-Chi earthquake, the most catastrophic and dramatic four will be discussed in greater detail. These are: Tsao-Ling rockslides, Juo-Feng-Err-Shan dip slope failure, stripping of Juo-Juo-Fong (99 peaks), and the Ku-Kuan to Te-Chi section （mileage 34K to 62K）of the Central Cross-Island Highway.Case study on the Tsao-Ling rockslides and the Juo-Feng-Err-Shan dip slope failure was also conducted. |
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| ASSESSMENT OF TSAO-LING LANDSLIDE AND LANDSLIDE LAKE |
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| 龔誠山 廖翊鈞 |
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| 921集集大地震、草嶺、崩坍、堰塞湖、草嶺潭 |
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| 草嶺堀山於民國88年921大地震作用下，再度發生大規模崩山事件，崩塌土石阻斷清水溪於上游形成堰塞湖（新草嶺潭），崩塌發生時正處於豐水期間，新草嶺潭水位急速上升，經濟部水利處為掌握草嶺殘坡及崩塌土體的安定狀況及新草嶺潭在洪水作用下的安全課題，另鑑於本區水文條件惡劣，必須進行緊急處置，乃在地震後儘速進行緊急處置評估，以作為短期處理方案的依據，另作為長期處理方案規劃之參考。 |
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| A large-scale landslide happened again at Tsao-Ling Mountain due to the effect of Chi-Chi earthquake on 21st September 1999, a landslide lake formed at upstream of Chi-Shue Creek after the debris blocked the creek. Because the event occurred in flood season, the water level raised up rapidly. In order to understand the stability of residue slope and felled debris and the safety problem of new Tsao-Ling Lake under the effect of flood, also the hydrological condition in this area is severe which made the disposal of natural dam becoming an urgent issue, the Agency of Water Conservancy of Department of Economy proceeded an emergent assessment immediately after the earthquake. The result provided a work guide in short-term and a reference in long-term disposals. |
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| SOIL LIQUEFACTION CHARACTERISTICS IN YUAN-LIN, WU-FENG AND NAN-TOU DURING CHI-CHI EARTHQUAKE |
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| 翁作新 褚炳麟 林炳森 |
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| 地震、土壤液化、現場調查、室內試驗 |
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| 集集地震為台灣百年來引致災害最大之地震。台灣中部地區震度甚大，許多地區，尤其是濱水砂質土壤，發生廣泛的土壤液化現象。彰化縣員林鎮、台中縣霧峰鄉、以及南投市之土壤液化災害最為嚴重，引致房屋受損，橋墩位移傾倒，堤防、擋土牆及水邊結構的崩塌與傾覆以及道路與農田的開裂與塌陷。本文報導在此地區所作之現場調查、鑽孔、現地試驗、室內試驗、以及其土壤液化特性分析的初步結果。此次地震引致土壤液化的資料將被引用為探討台灣土壤液化評估準則之依據。 |
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| Chi-Chi earthquake is the most damaging earthquake at Taiwan in a century. The shaking intensities at many places in the central part of Taiwan are very high, and extensive soil liquefaction occurred in many areas. Yuen-Lin, Wu-Feng, and Nan-Tou were especially hard hit with severe damages. Soil liquefaction caused house damages, movements and tilting of bridge piers, settlement and sliding of levees and water front structures, tilting and overturning of retaining structures, and cracking, lateral spreading and subsidence of roadways and farm fields. This paper presents the preliminary results of the field investigation, subsurface explorations, in-situ and laboratory tests, and analyses of the soil liquefaction during Chi-Chi earthquake. The information collected for the soil liquefaction during this earthquake will be used in the study of the liquefaction evaluation criteria for the soils in Taiwan. |
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| CASE STUDY ON SOIL LIQUEFACTION OF CHI-CHI EARTHQUAKE IN YUAN-LIN |
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| 蘇鼎鈞 王劍虹 |
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| 集集大地震、土壤液化。 |
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| 921集集大地震之芮式規模高達7.3，不僅對橋樑和建築結構等造成重創外，地震當時，台灣中部更有許多地方產生土壤液化現象，其中又以員林地區之大區域土壤液化最為嚴重且最廣為人知，而現場之液化現象包括有地表噴砂、地層下陷、建築物沉陷、建築物傾斜和溝渠等構造物水平側移等。本文將以員林地區集集大地震之液化評估為例，介紹土壤液化之評估流程與方法，包括現場之地質調查結果以及液化潛能之回饋分析，經比較SPT-N法和CPT法所計算出之液化潛能指數，其變化趨勢雖然類似，但數值差異卻很大，整體而言，以Seed方法配合液化潛能指數(PL)的評估結果與現地液化表徵的分布最為一致，即在本次員林地區集集大地震案例回饋分析中的表現最佳。 |
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| Chi-chi earthquake, with a magnitude of 7.3 (Ritcher scale), not only caused severe damages to bridges and buildings, but also resulted in soil liquefaction in many areas in central Taiwan. The Yuan-Lin in Chang-Hua County suffered extensive damages, including soil liquefaction, subsidence, settlement and tilt of buildings, lateral movement of ditches, etc.This article presents the process and analysis methods for liquefaction during Chi-Chi earthquake in Yuan-Lin, including site investigation and back analysis result. The liquefaction potential using SPT method and CPT method varies a lot, but the tendency is quite similar. Generally speaking, the results calculated by Seed’s method incorporated with liquefaction potential index well match the field evidence caused by liquefaction. It is considered that Seed’s method is the most suitable one in this study of liquefaction in Yuan-Lin in Chi-Chi earthquake. |
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| A STUDY OF GEOTECHNICAL DISASTER ON NANTOU COUNTY AFTER SHOCK |
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| 周鴻昇 楊清源
謝百鍾 余明山
高耀宏 |
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| 大地工程災害、斷層錯動、近斷層、基樁破壞、土壤液化 |
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| 本文針對921地震後南投地區公共工程及其鄰近地區所產生之大地工程災害，包括斷層錯動引致構造物之永久變形、近斷層基樁之破壞及土壤液化等。藉由測量、基樁鑽心取樣及地質調查等之成果，比對地震前後之差異，嘗試瞭解其災害程度與距離斷層地表破裂位置可能之關聯性，並探討現行液化評估方法本土之適用性。 |
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| The study presented herein focus on the geotechnical disaster occurred in the vicinity of Nantou county from the 921 Chi-Chi Earthquake, including fault movement induced deformation, pile failure nearby the fault zone and soil liquefaction. Based on the investigation results from survey and coring inspection of piles, the connection between damage level and its corresponding distance from the surface fracture of fault was probed. In addition, for well understanding the appropriateness of some familiar approaches applied in analysis of liquefaction potential, the borings data before and after quake were introduced. |
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| THE SEISMIC HAZARDS AND THE REHABILITATION OF THE TUNNELS IN CENTRAL TAIWAN AFTER CHI-CHI |
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| 王文禮 王泰典 蘇灼謹 林峻弘 諶家瑞 黃燦輝 |
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| 斷層、震害、龜裂、襯砌、隧道 |
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| 本文依據震後調查成果，整理1999年9月21日集集大地震造成台灣中部地區隧道之受損情形。針對隧道襯砌龜裂之特性，歸納代表性的受損型態，探討可能的受損原因；結果顯示受損程度與隧道是否經過斷層錯動帶、地質不良帶，或鄰近斷層錯動帶、震央、地表邊坡，以及隧道是否設置仰拱、是否有襯砌、襯砌是否有異狀、是否配置鋼筋等因素有關。文中亦介紹受損隧道之修復情形，並以數個隧道受損實例，探討隧道震害修復作業之流程與方式。 |
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| A systematic investigation of tunnel structures in central Taiwan after Chi-Chi earthquake has been conducted to evaluate the seismic effect on tunnel engineering. The damage patterns are summarized according to the patterns and the distribution of the cracks on the lining. The results show that the degree of damage is associated to the geological condition and the structural arrangement of the tunnel. Displaced fault zone passing the tunnel is definitely causing demolished damage. The geological weak zone, the distance from the epicenter and the unbalanced force of slope face also play an importance role. The seismic capacity of the tunnel relates to its structural arrangement, lined or unlined section, invert setup and reinforcement in the lining etc. Moreover, several examples are given to illustrate the rehabilitation procedures and technigues. |
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| EVALUATION OF DEBRIS FLOW AS POTENTIAL SECONDARY HAZARD CAUSED BY CHI-CHI EARTHQUAKE |
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| 林美聆 游繁結 林炳森 范正成 王國隆 |
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| 921集集大地震、土石流、二次災害 |
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| 921地震造成中部山區多處發生坍方，崩坍的土石材料堆積於集水區內，豪雨來時極易造成土石流，本文根據國科會委託之地震後土石流二次災害之研究，對中部地區進行廣泛之現地調查，並利用土石流發生特性擬定判定土石流危險等級之方法，危險等級區分為高度、中度及低度危險，本研究中總計調查土石流危險場址148處，其中高度危險計有49處，建議列入優先治理對象，分級成果可做為相關單位處理參考，同時對於新增之坡地型土石流進行深入之研究。 |
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| Due to the extensive slope failure caused by the Chi-Chi earthquake, massive amount of deposit material posed severe threat of potential debris flow hazard. In this study field investigations were conducted to identify and inventory the potential debris flow locations in the central region of Taiwan hit by the earthquake. Models for evaluation of hazard potential and risk were developed and risk assessments of the investigated areas were performed accordingly. The debris flows were rated as with high, medium, and low risk. A total number of 148 locations were investigated, and 49 locations were rated as with high risk. It is suggested that the locations with high risk should be mitigated with highest priority and more researches are need for the newly increased slope-type debris flow. |
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| CASE STUDY OF FOUNDATION REHABILITATION AFTER EARTHQUAKE |
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| 廖瑞堂 潘竹旺 俞清瀚 黃富國 |
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| 基礎、修復補強、扶正、頂升工法、灌漿工法 |
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| 921集集大地震後，災區部份建築物發生下陷傾斜，但上部結構大致良好的個案，該部份個案已進行建築物基礎之修復補強工作，以恢復其使用機能。基礎修復補強工法以採千斤頂頂升工法及灌漿工法最為常用，本文以頂升工法及灌漿工法各3處個案為例，說明其施工經過、成效及發生的若干問題，並比較該二種工法之優缺點及適用性。由案例探討可知成效良好的個案，通常都有周詳的事前調查及良好的施工管理，至於成效不佳或工期延宕甚久的個案，則大都缺乏良好的調查、計畫及施工管理，台灣地區基礎修復補強的經驗仍十分有限，且存在諸多問題，有待工程界共同努力加以改善。 |
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| Lots of buildings settled and tilted in the disaster areas attacked by the Chi-Chi earthquake. For the damaged buildings with stable upper structure, the foundation rehabilitation was performed to recover its original function. The underpinning method and grouting method were used most commonly for the foundation rehabilitation. A total of 3 remedial cases for each remedial method were studied in this paper and the construction processes, rehabilitation effectiveness and the problem encountered during construction were investigated and evaluated. As a result, the comparison of advantage/disadvantage and applicability between two methods are proposed. Results of this study indicate as the detail investigation prior to construction and the proper construction management were conducted during rehabilitation, the damaged foundation can be retrofitted effectively within an appropriate schedule; otherwise, the effective rehabilitation can not be reached and the construction duration will be postponed. Because the local experiences of foundation rehabilitation are limited in Taiwan and some major problems do not resolved yet, it is suggested that the techniques and abilities of foundation rehabilitation should be improved by the engineers with greater efforts. |
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| HOW TO GET ALONG WELL WITH FAULT AND EARTHQUAKE—GEOTECHNICAL DESIGN CONSIDERATIONS |
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| 陳斗生 |
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| 近斷層地震、地工設計、土壤液化、設計震譜。 |
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| 台灣位處地殼板塊衝撞介面，在本島形成過程中造成無數之斷層與伴隨之地震。由集集大地震災害情況檢討其震災之原因，包括法令、設計、營建至防災等問題，屬全面性且環環相扣。本文針對地工方面之防災建議地工調查與分析除應踏實而完整外，應加強"近斷層地震"之研究，對動態水、土壓力、土壤液化之分析與防災設計，並應針對各地之地質構造與地層變化特性，分別提出最大可能來襲地震與或然率分析之設計反應譜供結構設計採用。 |
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| The Island of Taiwan is at the collision zone of Euroasian and Phillippine Sea Plates, resulting in numerous faults and earthquakes in the process of the Island's formation. Wide range of causes causing diastrous damages during the Chi-Chi Earthquake, including code, regulations, design, construction to disaster prevention system, etc. Regarding geotechnical engineering, in addition to thorough site investigation, the "near fault seismicity study" is imperative for Taiwan's seismologists; the earthquake effect on the earth pressure, water pressure, liquefaction potential analysis and its mitigation measures should be considered seriously; and the design spectrums for both the Maximum Credible Earthquake and the Maximum Probable Earthquake spectrums considering the geologic formation and site soil conditions should be included in geotechnical site investigation reports for structure engineers' use in the design. |
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