以3-D數值方法探討大規模崩塌集水井及排水廊道地下排水系統之運作效率

3-D Numerical Investigation of the Operation Efficiency of Subsurface Drainage Systems using a Drainage Well and Drainage Gallery for a Large-Scale Landslide

10.29417/JCSWC.202206_53(2).0001

林德貴(Der-Guey Lin)；張國欽(Kuo-Ching Chang)；劉文宗(Wen-Tsung Liu)；洪勝雄(Sheng-Hsiung Hung)

深層地下排水系統 ； 集水井 ； 排水廊道 ； 潛在滑動區 ； Deep subsurface drainage system ； drainage well ； drainage gallery ； potential sliding zone

中華水土保持學報

53卷2期（2022 / 06 / 01）

67 - 91

繁體中文

為探討梨山大規模崩塌地滑區深層地下排水系統（以下簡稱地下排水）之規劃配置方式及其排水運作行為對邊坡穩定性之影響，本研究依據梨山地滑區之鑽探、地質調查、地形等高線、岩土力學試驗、以及地下水水位（以下簡稱水位）監測等資料，建立梨山精華區中部潛在地滑區之三維數值模型，並進行地下排水穩態分析及邊坡強度折減穩定分析。同時，採用水位、滑動區位、以及滑動深度之監測成果與分析結果進行比對，來驗證三維數值模型之有效性。最後，藉由比較地下排水中九個工程單元（7座集水井及2條排水廊道），在不同運作情境下求得之水位洩降貢獻百分比（PC_(GW) %）、穩定性安全係數（FS）之提升百分比（△FS %）與提升貢獻百分比（PC_(FS) %）、以及潛在滑動區位之改善成果，即可了解地下排水中，各工程單元運作時之相互影響機制及其排水效益。在地下排水各工程單元陸續完工後，原來位於北側主要潛在滑動區之範圍及位置，由於地下排水後其穩定性受到改善，因此會縮小並轉移至西側嶺線附近之區域。同時，地下排水中之各工程單元，會隨著工程進展依序加入運作發揮其排水功能，並逐漸提升地滑區邊坡之穩定性（FS=1.131→1.300）。

To investigate the optimal configuration and performance of subsurface drainage systems (comprising nine engineering units, seven drainage wells, and two drainage galleries) in relation to the Li-Shan landslide, a 3-D numerical model of the central area of the landslide was generated based on a substantial amount of information (boring logs, contour topography, geological surveys, soil/rock laboratory tests, and groundwater monitoring data). Steady-state subsurface drainage analysis and slope stability analysis using a strength reduction method were performed systematically. The validity of the numerical model was verified by comparing the coincidences of numerical results with monitoring data in terms of groundwater variation and location/depth of the potential sliding zone. An evaluation of the interactive effects and drainage efficiency, in relation to the sequential operation of the nine engineering units, was performed using the contribution percentage of groundwater drawdown (PC_(GW) %), increasing percentage (△FS %) and enhancement contribution percentage (PC_(FS) %) of the factor of safety (FS), and the location of potential sliding zone. Upon completion of the subsurface drainage system, the main potential sliding zone on the northern side of the landslide area was stabilized due to effective groundwater drawdown, and it was eventually transferred to the adjacent area of the western ridge. In addition, as the subsurface drainage construction was progressing and becoming gradually operational, the stability of the potential sliding zone was enhanced with an increase in the factor of safety (FS=1.131 → 1.300).

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