| 摘要: | Burland (1987)提出大地工程分析包含三種模型：地質模型、地面模型與大地工程模型。地質模型表現出現場 工址的地質條件，包含地質史、地質材料、地下水與層面位態等等；地盤 模型是將地質模型加上地工參數；大地工程模型是根據地面模型，針對個別要求做出預測模型。 由此可知，要做好大地工程分析，就必須考慮到地質模型不確定性。本研究分別從邊坡穩定性及崩滑塊體之運移距離來探討2010年國道三號3.1k崩塌案例受地質模型不確定性之影響。 葉致翔等人 (2021)透過有三種不同取得國道三號滑動面傾角參數的方法：(1)經濟部中央地質調查所區域地質圖；(2)現地以 地質羅盤量測；(3)LiDAR輔助判釋資料，藉由蒙地卡羅法來分析，並用極限平衡法計算出各個安全係數最後得出破壞機率。本研究以此做延伸，將滑動面以坡頂、滑動面中心與坡趾做支點來改變傾角，並考慮滑動塊體 體積 因傾角改變而改變的情形下，計算坡體滑動破壞機率。結果顯示以坡頂改變傾角較為合理，其破壞機率分別是地質調查所區域地質圖 為地質羅盤為LiDAR則趨於0%，說明不同調查方法有不同的精度，LiDAR所得到的傾角標準差與地調所地圖及地質羅盤相比較小，因此破壞機率也相對較小。葉致翔
等人(2021)的破壞機率分析結果分別是地質調查所區域地質圖為20.6%；地質羅盤為2%；LiDAR則趨於0%，說明考慮傾角變化對塊體重量的影響會增加破壞機率但幅度不多，主要還是傾角不確定性影響較大。
本研究亦探討節理分布的不確定性對於塊體崩移特性的影響，透過現場調查報告建立出與現場崩塌情形較為相似的一組數值模型，其走向節理個數為 8個，傾向節理個數為5個。透過改變走向與傾向節理的個數，建立出相對應的數值模型，觀察各個模型的坡頂位移、運移距離、崩落區寬度和崩落區面積，使用點估計法計算出各項的機率密度分布，進而計算各項的風險評估。結果顯示傾向節理變異性對於坡頂位移之影響較走向節理大；此案例的運移距離不受節理分布不確定性影響，有極高機率會直接淹沒南北雙向車道；崩落區寬度受節理分布不確定性影響可能不大；走向節理的變異性對
雙向車道；崩落區寬度受節理分布不確定性影響可能不大；走向節理的變異性對崩落區崩落區面積之影響較大。面積之影響較大。;Burland (1987) proposed that geotechnical analysis includes the assumptions of three models: Geologic Model, Ground Model and Geotechnical Model. The geologic model expresses the geological conditions of the site, including geological history, geological materials, groundwater and formation conditions, etc. The ground model represents the physical and mechanical properties of the geo-materials. The geotechnical model consists of theoretical or simplified assumptions of a predictive model for the analyzed case. In order to achieve a more representative geotechnical analysis result, the uncertainty of the three models must be considered. In the current study, we have focused on the importance of the geological model in a typical geotechnical analysis.
In this study, the impact of the geological model uncertainty on the National Highway No. 3 (NH-3) landslide event was discussed from the perspective of slope stability and debris run-out parameters. Yeh et al. (2021) obtained the sliding planes dip angles of NH-3 from three sources, which are: (1) the regional geological map of the Central Geological Survey, MOEA; (2) site investigation on the sliding plane after the sliding event; (3) the LiDAR data. Yeh et al. (2021) used the Monte Carlo simulation and the limit equilibrium method to calculate safety factors, and finally obtained the probability of failure of slope sliding, however, without considering the volume change of the sliding block due to the change of the dip angle. In this study, we have incorporated the change of debris volume with dip angle in the Monte Carlo Simulation. The results show that with the change of the dip angle (rotation at slope crest), the failure probability is 26.5% (as compared to Yeh et al. (2021) at 20.6%) with regional geological map information; 4.1% (as compared to Yeh et al. (2021) at 2%) with site investigation information after the sliding event; close to 0% with LiDAR-derived data (similar to Yeh et al. (2021)). The above results indicate that different surveying methods may result in different data accuracy. LiDAR-derived dip angle yielded the smallest standard deviation among the three investigation methods, therefore the probability of failure is relatively small.
To explore the uncertainty of joint distribution on the debris run-out parameters, this study established a set of numerical models that are similar to the landslide case through on-site investigation reports. A number of corresponding numerical models were established by changing the number of the joints along the strike and dip directions of the slope. The debris run-out parameters, including the slope crest displacement, toe run-out distance, debris accumulation width and area of each model are analyzed using point estimate method. Probability Density Function of each parameter is analyzed and the risk assessment (probability of exceedance) of each debris run-out parameter was then calculated. The results show that the uncertainty of dip joints has a greater impact on the slope crest displacement than that of the strike joints; the run-out distance of this case is not affected by the uncertainty of the joints, and there is a very high probability that the highway is directly covered by the landslide debris; the width of the accumulated debris is not affected much by the distribution of joints. Finally, the variability of strike joints has a large effect on the coverage area of the accumulated debris. |
