大規模崩塌區集水井地下排水行為及穩定效果之模擬

Modelling the Performance and Stabilization Effect of Subsurface Drainage using Drainage Well for Large Landslide

林德貴(Der-geuy Lin) ； 張國欽(Kuo-Ching Chang) ； 王勝賢(Sheng-Hsien Wang) ； 陳榮俊(Jung-Chun Chen)

《中華水土保持學報》 52卷2期 (2021/06) Pp. 73-88

https://doi.org/10.29417/JCSWC.202106_52(2).0002

摘要

自從2009年莫拉克（Morakot）風災之後，多次颱風引發之暴雨事件，造成嘉義縣瑞里村幼葉林崩塌區發生長期間歇性大規模地滑移動。為解決此地滑問題，2018年相關政府部門已完成兩座集水井（包含井內多階橫向集水管）地下排水工程之設計與施工，以洩降崩塌區之水位，並提升其穩定性。本文介紹崩塌區之監測結果，以及地下排水工程之設計與施工考量。同時，採用三維（3-D）數値模擬技術，來檢視地下排水工程之集排水效能及其對邊坡之穩定效果。數值模擬結果顯示，在颱風暴雨期間，集水井地下排水工程能加速排除崩塌區之入滲雨水，大幅洩降地下水水位，並有效減緩邊坡穩定性快速下降之不良影響，使邊坡穩定性在暴雨狀態下仍能維持在可接受且滿足設計要求之安全範圍內。

關鍵字

地下排水 ； 集水井 ； 橫向集水管 ； 地下水水位洩降 ； 邊坡穩定性

並列摘要

The You-Ye-Lin landslide has caused long-term intermittent large ground movements during torrential rainfall since Typhoon Morakot occurred in 2009. To solve the landslide problem, the Soil and Water Conservation Bureau designed and constructed a subsurface drainage system consisting of two drainage wells (vertical shaft with multilevel horizontal drains) to draw down the groundwater table and stabilize the slopes made unstable from the landslide. This study investigated the field-monitoring and in situ conditions of this system, with an emphasis on the design and construction of subsurface drainages, and evaluated the system's efficiency at stabilizing the slopes using 3D numerical analyses. The numerical results demonstrated that the subsurface drainages were functional and capable of accelerating the drainage of rainwater caused by high-rising groundwater levels during the torrential rainfalls of typhoon season. The large quantity of groundwater drawdown achieved by the subsurface drainages protects the slopes from fast deterioration and maintains the slopes' stability to satisfactory design and safety standard.

並列關鍵字

subsurface drainage ； drainage well ； horizontal drains ； groundwater drawdown ； slope stability