廢棄坑道之地盤下陷潛在災害調查主要研究對象為地下採礦坑道、鐵公路的隧道以及軍事隧道等等，因其這類資訊取得可及性極低、地下地質資料的缺乏與專業性等條件的限制，災害潛勢的調查與評估顯得相當缺乏。由於這類廢棄坑道常會引起地表變形（surface deformation）或地盤下陷（ground subsidence）等災害，因此對地上建物與民眾安全具有潛在不確定性之災害影響。本計畫工作於97、98兩個年度進行北北基都會區之調查與災害潛勢評估之初步結果，引進多項技術之結合，輔助災害潛勢之驗證。其包括多下陷槽之數學模式結合了GIS-3D空間分析、上覆岩體厚度以及岩體強度分級（試作）的技術提供了災害潛勢高低之比較因子、現地調查之災害案例訪談與水準測量進行台北縣中和市東運瓷土礦區之案例試作，以及建立專家安全評估模式等等，目的是希望透過多方技術的整合來逐步建立台灣地區地下坑道所引發之地盤下陷災害相關資訊，從而建立適用於台灣之災害潛勢分析模式。而99年度計畫之主要調查區域為桃園、新竹以及苗栗等縣市地區（計11處），另於前兩個調查年度中有必要持續調查之重要案例：東運瓷土礦區，係因上述之水準測量方法於上年度在該礦區初步獲得下陷之驗證，值得持續監測研究之。經由上年度之工作執行經驗中，雖初步以GIS評估模式將下陷量推估範圍與岩體等厚度（定量）、下陷量推估範圍與岩體強度分級（半定量）來進行災害潛勢高低之界定。然仍需更多案例經驗值來輔助地盤下陷災害之潛勢範圍定義，以提供一個較快且合理之初步評估模式，期能建立一套適用於台灣地區因廢棄坑道引發之地盤下陷災害潛勢評估模式。此外，本計畫的成果可應用在地質法草案(96.5.2)第六條「中央主管機關得將有發生地質災害之虞之地區，公告為地質敏感區」，做為此一類地質敏感區劃設的重要參考。
In Taiwan, the ground subsidence hazards could be caused by the abandoned tunnels（adits or shafts）excavated underground around coal mine area. The locations of underground excavations did not be identified clearly, nor did the geospatial relationship in subsurface. So the main purpose of this project is to establish the risk assessment of ground subsidence hazard and to define the potential risk area. According to experience from last two year’s work, the locations of ground subsidence cases seem to coincide with the prediction of multiple subsidence troughs model. The rock intensity testified by unconfined compressive strength shows the roof strata of underground mined area are ranged from moderate to weak. And the R.Q.D values measured from field outcrop profiles have been recalculated and become much reasonable. In the other methodology of ground subsidence monitoring, though the interpretation of D-InSAR analysis shows well comparison with subsidence model in the detected area, Tonyung clay mine area in Chung-Ho City of Taipei County, its application is still limited by the ground covers, such as plants as well as slope degree. So, the level measurement might be provide an alternative way to monitor the subsidence phenomena existed in abandoned mine area. The risk evaluation of subsidence hazard has been defined by GIS model according to more than 30 in situ cases investigated. Base on predicted subsidence and covering thickness, it’s classified into three categories by matrix expression： within the stope area,the high potential area defined as : predicted subsidenc is larger than 20 cm and covering thickness less than 50 m; the low potential area defined as : predicted subsidenc is less than 20 cm and covering thickness larger than 50 m. The other area are called moderate potential area. Finally, trend surface analyzed by subsidence data collected from Tonyung clay mine shows well comparison with subsidence troughs. It is worthy to be carried on next year work and the result should be compared with theoretical subsidence model.
