- 學位論文
應用電氣探測法評估瀨頭崩塌機制之研究
Study on the Mechanism at Laitou Landslide Area by Earth Electrical Logging Method
摘要
曾文水庫上游集水區龍美聚落南側之瀨頭林道，民國98年8月莫拉克風災期間發生大規模崩塌，透過歷年航空影像判釋發現此崩塌為舊有崩塌地，而主要地質為長枝坑層佔大部分，且下游河川侵蝕速率快，加上地形條件欠佳與環境外力影響下，倘若崩塌範圍持續擴大，恐對龍美聚落有安全上之威脅。莫拉克風災後此崩塌之治理工程已完工，故本研究於崩塌地上方進行監測，並應用電氣探測技術進行相關分析研究，以瞭解龍美聚落與相鄰瀨頭崩塌地層之分佈特性。 研究結果發現，崩塌地治理工程完工後，龍美聚落近瀨頭崩塌地集水區之嶺線旁，經孔內傾度觀測管試驗發現地表下10m處有位移情形，進一步應用電氣探測法展繪ρa–a地電阻剖面圖，依剖面圖等ρa線性排列水平、垂直、封閉、豎起、下凹、反折等特性，並配合地表勘查結果，所推測滑動面及滑動深度相當符合。 此外，應用雙對數ρa– a曲線型態特性分析，先行配合一孔鑽探資料，其他無鑽孔位置能依線性上升、下降、坡折、抖狀、豎曲線、反折等特性能有效劃分地層。
並列摘要
In August 2009, Typhoon Morakot caused a large scale landslide at Laitou forest road, which is located on the south side of Longmei settlement in the upstream catchment of Zengwen Reservoir. Through the interpretation of satellite images over the years, the collapsed land was found to be pre-existing. Changchikeng formation is the main geological setting in this region. High erosion rate in the downstream area, unfavorable geographical conditions and influence of environmental forces may contribute to the continuous expansion of landslide area, which imposes threats to the safety of Longmei settlement. Regulation project for the disaster after Typhoon Morakot has been completed. Through monitoring the collapsed land from above and applying the Earth Electrical method to conduct relevant analyses, this research aims at understanding the distribution characteristics of Longmei settlement and the neighboring Laitou collapsed strata. According to the findings of the research, a subsurface displacement at 10 cm depth was observed (via an inclinometer) next to the ridgeline within the catchment of Laitou landslide area near Longmei settlement. Then, the Earth Electrical method was applied to plot the ρa–a resistivity image profile. The proposed slipping plane and slipping depth considerably matched the results derived from observing features of ρa-linear array of the profile: horizontal, vertical, closed, erected, waning and inflective, and from ground surface survey. By applying double logarithmic analysis on ρa–a curve patterns combined with core drilling data, strata for locations lacking drilling records can also be effectively classified in accordance with features such as linear rise, decrease, break of slope, tremor, vertical curve and inflection.