2013-01-012024-05-15https://scholars.lib.ntu.edu.tw/handle/123456789/663641摘要：本研究之目的在於了解位於地表下的斷層尖端擴展受上覆土層對斷層跡修飾的效應，以及探討斷層作用時，隨斷層尖端擴展主要變形區內土體內應力、應變的空間分布及其對結構物之影響，這些研究在學理上對斷層帶退縮距離的決定相當重要。另外本研究也會加強對斷層錯動時土壤與結構互制的了解，針對直接承受斷層錯動衝擊的結構物，探討並提出如何強化結構設計、減少衝擊的程度等地震減災的可行方法。 目前對於活動斷層近地表變形特性的研究在研究方法大致上可以分為現地調查、物理模型試驗以及數值分析等三大類，本計畫之研究為突破單一方法學提出結果之侷限性，因此併用現地調查、物理模型實驗(離心機砂箱試驗、1g砂箱實驗)及數值分析之方法，分別進行基本行為觀察及定量分析。 本研究計畫全程為期四年(100~103年)，今年之進程為第三年(102年)，本年度選擇橫移斷層(米崙斷層、Hayward Fault)為主要研究對象，透過槽溝及斷層沿線之現地調查，加上古今地震研究與記錄、槽溝剖面等文獻&#33987;集來探討斷層兩側岩層變形行為，如剪切帶發育、遷移、影響範圍及影響參數等；並且利用中央地質調查所之工程地質資料庫的鑽孔資料進行土壤力學的統計分析，以提出建議的簡化剖面。另外，本年度的砂箱實驗分為1g實驗及離心機實驗兩部份，1g實驗進行傾角90度之橫移斷層砂箱實驗，探討斷層錯動時上覆土層變形行為；離心機實驗則繼續針對前二年所研究之斷層型態(逆、正斷層)進行更多項實驗，包含土壤與結構物互制及砂黏土互層等實驗。數值模擬方面將以PFC3D及PFC2D為分析工具，研究團隊目前已對模擬砂土時所使用之微觀參數有很好的掌握程度，但對於模擬黏土時所使用之微觀參數該如何選取仍需進一步研究研究。因此，本年度數值模擬的工作一部份將擺在黏土材料之微觀參數，而砂土材料的部份則是綜合砂箱實驗配置與實驗所得之材料參數進行數值分析，以PFC3D進行1g之橫移斷層數值模擬，探討斷層錯動時上覆土層變形行為；以PFC2D進行逆、正斷層土壤與結構物互制數值模擬。再將數值模擬與砂箱實驗驗證過之結果，以全尺度數值分析探討斷層作用時上覆土層變形行為，及其對人工結構物之影響，並提出較合理的安全性探討指標，作為判斷建築物或設施安全性的參考。 本計畫第一年主要研究對象為逆斷層(車籠埔斷層)，第二年主要研究對象為正斷層(山腳斷層)。第一年的研究結果顯示，以橫跨集集地表破裂跡的竹山槽溝及相鄰地區的調查結果為例，近斷層之變形特徵無法由航照或衛星影像判釋得知，雖集集地震距今已10年以上，但部份現地地表仍保留震後的重要地形變化的特徵(如斷層的大致崖高、錯動方向與錯距)。砂箱實驗方面：鑑於過去對影響斷層跡出現在地表位置的因素之研究，優先探討上覆土層厚度及相對密度這兩個變因，由第一年的離心機實驗成果顯示，傾角60o的斷層角錯動時，在1g及10g的試驗條件下，地表高程劇烈變化影響範圍約等於覆土層厚度；而相對密度的大小，並不會顯著影響表土層劇烈變形的範圍。數值分析方面：第一年分別嘗試非連續體分析法(PFC2D程式)、連續體模式之有限差分法(FLAC程式)及邊界元素法進行砂箱成果或現地變形剖面之模擬。研究成果顯示，利用邊界元素法可推求逆斷層觸發地表變形帶中應變與離斷層跡相對位置的關係；有限差分法(FLAC2D)可直接求取逆斷層滑移歷程下，上覆土層應力及應變場分布情形；分離元素法(PFC2D)可觀察不同土層材料及組成(純砂、純黏土、互層)，在不同逆斷層滑移量下，地表變形特性。經過比對，非連續體分析法的優點在於它最能模擬接近地表土層之粘土或砂土不同的變形行為，對土層中變形剪切帶發育行為較為相符，而且具有模擬斷層多次歷史活動所產生地表附近生長斷層與生長地層特性之潛力，因此本研究團隊選用為接下來三年的主要數值模擬工具。 在第二年的研究中，本團隊利用地調所提供之「活動斷層岩心調查系統」重繪井錄，共計48口。繪製出來的成果有助於山腳斷層位置的研判，以成子寮剖面為例，在SCF5-SCF6之間可以看到山腳斷層為生長斷層的現象。另外也透過整理仙渡超高壓變電所鑽探資料，提出進行山腳斷層數值模擬之簡化土層可為為四層。砂箱實驗方面，前二年共進行了38組60度正、逆斷層的離心機實驗，結果顯示：純砂土的情況下，逆斷層之剪切帶的影響範圍約等於覆土厚度；正斷層之剪切帶的影響範圍約等於覆土厚度的0.8倍。純黏土的情況下，逆斷層之剪切帶的影響範圍約等於覆土厚度的2.2倍；正斷層之剪切帶的影響範圍約等於覆土厚度的1.9倍。而數值分析方面：鑑於第一年之嘗試的結果，得知非連續體體分析法的優點在於它最能模擬接近地表土層之粘土或砂土不同的變形行為，對土層中變形剪切帶發育行為較為相符，而且具有模擬斷層多次歷史活動所產生地表附近生長斷層與生長地層特性之潛力，因此第二年研究主要以非連續體體分析法(PFC2D程式)進行正斷層及生長斷層之模擬。正斷層的部份，透過比對離心機砂箱實驗的地表變形，本研究提出模擬砂土的微觀參數；生長斷層的部份，透過比對1g砂箱實驗的剪切帶發展可以看到在同樣覆土厚度的情況下，剪切帶在有生長地層的環境下發展至地表所需要的基盤錯移量比沒有生長地層的環境下還要少。綜合第二年的結果可以看到，更深入研究鄰近大台北都會區的山腳斷層是相當重要且必要的。<br> Abstract: The determination of theoretical setback widths used to avoid the earthquake hazard due to distortion of ground induced by faulting is deemed as essential as the understanding on how propagation of fault-tip affects the width of deformation zone on the ground of the soil/rock mass, the spatial distribution of strain and stress within the zone, and the foundation response. Furthermore, modification of the design methods of the foundations by studying the interaction among the fault rupture, geomaterial and foundation is a useful means to mitigate an earthquake hazard associated with soil structure interaction inducing by faulting. Currently the approaches to investigate the near ground deformation due to reactivation of active faults can be categorized as (1) field investigation (2) laboratory testing and (3) numerical modeling. In order to break through the limitation of individual approach, field investigation, numerical modeling along with laboratory testing, including sand box experiments under both 1-g and centrifuge conditions (hereinafter referred to as centrifuge testing), will be conducted for characterizing and quantitating deformation induced by faulting in this study. This year (2013) is the third year of this research project with 4-year duration. In this year, strike-slip fault is chosen as the major focused fault type. The generalized stratum profile is proposed from site investigation, historical seismic records, and soil boring database from CGS. Laboratory testing for simulation of strike-slip fault will be focusing on dip angle of 90 degrees under 1-g condition using sand boxes. Simulations of reverse and normal faults under centrifuge conditions will continue as what has been performed for the past two years. In terms of numerical analyses, PFC2D will be employed for simulation of reverse and normal faults as previously performed; furthermore, PFC3D is chosen to simulate the deformation characteristics of strike-slip faults. As for material properties in numerical modeling, sandy material can be modeled pretty well comparing centrifuge tests and PFC2D simulation results, however, for cohesive material (such as clay) properties in numerical modeling, the relationship between macro and microscopic material properties is yet to be explored in this year. For normal and reverse fault simulations and analyses that were performed in the past two years, brief results are summarized as following: (1) Shanchiao fault is a growth fault based on the logs of SCF5 and SCF6. In addition, generalized profiles for numerical simulations of the Shanchiao fault was proposed based on soil boring information from Shiendu Extra-High Voltage Substation construction site. (2) A total of 38 centrifuge modeling tests were conducted for normal and reverse faults with a dip angle of 60°. Results show that for sandy material, the affected extents are approximately equal to the thicknesses of the overburden layer by reverse faulting and approximately four-fifths induced by normal faulting, respectively. For models with clayey material, the affected extents are approximately 2.2 times the thicknesses of the overburden layer by reverse faulting and approximately 1.9 times induced by normal faulting, respectively. (3) Simulations for growth normal faulting were also performed using PFC2D. Results have shown that a smaller offset displacement was required for the shear band to be propagated to the ground surface, while for a normal fault without any sedimentation layers, the required distance is larger.活動斷層近地表變形離心機砂箱實驗土壤結構互制退縮距離減災工法active faultsnear-ground deformationcentrifuge testingsoil -structure interactionsetback widthhazard mitigation strategy