Evaluating Geological Model Uncertainty Caused by Data Sufficiency – Using Groundwater Flow and Land Subsidence Modeling as the Example

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题名:	Evaluating Geological Model Uncertainty Caused by Data Sufficiency – Using Groundwater Flow and Land Subsidence Modeling as the Example
作者:	阮國強;Nguyen, Quoc Cuong
贡献者:	應用地質研究所
关键词:	地質模型不確定性;資料充足性;地質知識;鑽井數目;融合地物資料;地層下陷;Geological model uncertainty;Data sufficiency;Geological knowledge;Borehole number;Geophysical data assimilation;Land subsidence
日期:	2021-07-26
上传时间:	2021-12-07 13:24:49 (UTC+8)
出版者:	國立中央大學
摘要:	地層下陷是無聲的災害是近年在世界上受到多許多的關注，特別在人口稠密與眾多建設的區域。學習與預測地層下陷的速度以及釐清土體壓縮的因素已景有許多的研究與認知。然而，現有的文獻中較少討論地質模型不確定性對地層下陷的影響評估。本研究使用 GMS 這套商業軟體來模擬地下水流與地層下陷來評估地質不確定性。在沙克爾頓計畫中，建立一個合成模型並假設此模型為初始模型。以地質知識、不同數量的鑽孔資料以及考慮鑽井與地電阻實驗的複合資料，此三種條件來發展並建立數個三維地質模型並運用三維暫態地下水流模式(MODFlOW)與下陷模式(SUB)發展與模擬。透過計算原始模型的均方跟誤差(RMSE)與決定係數來比較與評估不同地質模型所產生的結果，從結果上可以得知，想比於以不同數量的鑽井數所建立的模型於使用地電阻校正後的鑽井資料所產生的結果會有最好的結果。結果還顯現了，規定的邊界條件限制了邊界附近的下陷量，水力傳導系數的值顯著的影響地層下陷時的遲滯效。根據這些結果，地質學家們，可考慮將地球物理的實驗結果搭配鑽井資料來做為評估地質模型建構的方針，以降低地值模型對特定地區所產生的不確定性。;Land subsidence is a silent hazard that currently attracted great noticed around the world, especially in populated and large building areas. Studying and predicting land subsidence rate and understanding the factors that cause soil compaction are widely studied and understood. However, the uncertainty in the geological model which largely affects land subsidence assessment is less considered in literature. This study used a commercial software, Groundwater Modeling System (GMS), to operate groundwater flow and land subsidence simulations for the assessment of the geological model uncertainty caused by various conditions of data sufficiency. A synthetic geological model, constructed by the Shackleton project, was adopted as the original model. Three scenarios as whether including geological knowledge, different numbers of boreholes, and a combination of the borehole data and the resistivity tomographic data (provided by the Shackleton project) were considered to build new 3D geological models. Transient groundwater flow models (MODFLOW) and subsidence models (SUB) were developed and simulated based on the constructed geological models. The numerical results from these geological models were compared to that of the original model by using the root mean square error (RMSE) and coefficient of determination (R-squared). The results showed that using the resistivity tomographic data with the cokriging correction of borehole data was the best case. The results also indicated that the prescribed boundary condition constrains the subsidence quantity around that boundary, as well as the value of hydraulic conductivity significantly affects the delay behavior in land subsidence calculation. Based on these results, geologists can assess the appropriate stratagem for geological model construction and consider combining the geophysical results with borehole data to mitigate the uncertainties of the geological model to a specific study area.
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