| 摘要: | 針對土壤液化評估及減災，大地工程師及科學家已經提出許多不同的評估方法。根據一項新的研究發現，由於地震造成的土壤超額孔隙水壓與地震波參數CAV5(註一)具有相當大的關聯性，所以一項以CAV5為基礎用來評估土壤液化的新方法也因此被提出。但雖然該研究證實CAV5與土壤液化有高度關聯性，其中的數值模型及參數卻尚未被詳細探討。因此本研究案的主要目的是接續該項研究進行CAV5與土壤液化數值模型的開發，緊接著利用此數值模型去評估台北地區發生土壤液化的機率，尤其一旦當位於台北附近的山腳斷層誘發與921類似的大地震。 在第一部分的研究中，主要的研究方法為利用實驗方式去研發CAV5與土壤液化的數值模型。更明確地說，為了降低大地工程研究中規模效應的影響，本研究階段將在本校中央大學大地工程離心機實驗室進行模型試驗，緊接著用logistic迴歸對離心機實驗所得到的數據進行分析，研發出新的logistic數值模型用來評估土壤液化潛勢與CAV5的關係。 在第二部分的研究中，主要的研究方法為利用地震危害度模型進行台北土壤液化潛勢分析；其中必須說明的兩點研究前提如下:1)台北附近的山腳斷層可能會在未來誘發與921類似的大地震；2)第一階段研究得到的CAV5土壤液化數值模型也將成為本階段研究中重要的一項根據。 本研究案對於大地工程學術界以及台北地區土壤液化潛勢評估的主要貢獻如下:第一，本研究所得到的CAV5與土壤液化關係的數值模型將成為此CAV5土壤液化評估法的最後一塊拼圖，接續前人研究發現CAV5與土壤超額孔隙水壓具有高度的關聯性；第二，利用第一階段研究成果所獲得的台北地區土壤液化潛勢圖將對本地區土壤液化潛勢提供另一種新觀點，根據此類型土壤液化評估方法結合山腳斷層誘發大規模地震的可能性。 註一: 類似常用的地表最大加速度(PGA)，CAV5為另一種描述地震波大小的參數；詳細說明請參見計畫書中圖二所示。 ;A variety of studies have been reported for soil liquefaction assessment and hazard mitigation. According to a recent study, a ground motion intensity measure called CAV5 (cumulative absolute velocity with a 0.005 g cutoff) was found having a strong correlation with pore pressure buildup in soil, and therefore it is suggested to be utilized in soil liquefaction assessment. However, what was missed in such studies is the correlation model between CAV5 and soil liquefaction potential. As a result, the first objective of the proposed research is to establish a model that can estimate soil liquefaction potential for a given CAV5, which is referred to as Part I of the research. Next, the research will apply the newly developed logistic model to evaluate soil liquefaction probability in Taipei metropolitan areas subject to a scenario that the Shanchiao fault in Taipei could induce a major earthquake, which is the Part II of the study. The methodology for developing the new CAV5-based soil liquefaction model (Part I) is based on experiments. Specifically, a series of centrifuge tests will be conducted in Geotechnical Centrifuge Facility of National Central University (the institution of PI Wang), followed by logistic regression analysis on the data obtained. As other geotechnical studies, we utilize a geotechnical centrifuge to create our prototype model that is representative (or big) enough to reduce the scale effect in the geotechnical physical modeling. The methodology for Part II, assessing soil liquefaction probability in Taipei subject to the scenario of the Shanchiao fault inducing a major earthquake, is basically following the framework of seismic hazard analysis, with a variety of input data from fault length and slip rate to ground motion prediction equations. After the scenario-based CAV5 is determined with the analysis, it will be substituted into the CAV5-based logistic model, developed in Part I, to evaluate soil liquefaction probability in Taipei metropolitan areas with such a new approach. The key contribution of the proposed research is as follows: i) the CAV5-based liquefaction assessment model completes the framework of CAV5-based liquefaction analysis, considering CAV5 is strongly correlated with pore pressure buildup in soil, and ii) the application of the newly developed model to soil liquefaction investigation in Taipei can provide more insights to liquefaction microzonation for the study area, from a different perspective than previous studies based on conventional procedures. To help comprehend the key aspects of the proposal, a graphical executive summary was prepared and shown in Fig. 4 of the proposal. Please refer to it for a quick overview of the proposed research. |
