地下水水質與邊坡崩塌及崩落型土石流發生之關係─以南投地區為例

Abstract

本研究以滲流槽模型試驗，模擬南投地區之地下水水質對邊坡崩塌及崩落型土石流發生之影響。試驗土樣採自南投縣信義鄉神木村及豐丘村之土壤重模製作75˚邊坡至滲流槽內，經供水設備由滲流槽一端控制水頭高度，促使土體試樣邊坡產生破壞，並同步蒐集水質資料及記錄土體變位，藉此分析地下水水質與邊坡破壞之間的關聯。 試驗結果顯示，土體變位與土體下游處之滲流水電導度值及硫酸根離子濃度有非常顯著的相關。當土體破壞時，土體下游處滲流水電導度之門檻值為39.2µs/cm，而土體下游硫酸根離子濃度之門檻值為9.98mg/L。利用土體下游電導度值與土體垂直變位及水平變位迴歸分析，決定係數各為0.7220及0.8252，這表示以土體下游電導度值推估土體變位具有不錯的預測效果。

The objective of this study is to investigate the relationships among the occurrences of landslides, slump type debris flows and the quality of groundwater in Nan-tou area. Soil samples for the tests were collected from Shen-mu and Fen-chiu in Nan-tou to prepare for the remodeled test with slope of 75˚ in a specially designed seepage tanks. A water supply system was used to control the pressure head to cause soil slopes to be failed, quality of groundwater and displacement of the soil sample were collected at the same time. The tests were then conducted to investigate quality of groundwater while the soil slopes failed. The testing results showed that there is positive correlation among the concentration of EC and SO42- of the seepage water at downstream of the soil slopes. While the soil slopes failed, the threshold value of the concentration of EC and SO42- of the seepage water at downstream of the soil slopes were 39.2µs/cm and 9.98mg/L. The coefficient of determination among the vertical displacement of soil, horizontal displacement of soil and the concentration of EC of the seepage water at downstream of the soil slopes were 0.7220 and 0.8252, it means that the displacement of soil can be predicted by the concentration of EC of the seepage water at downstream of the soil slopes.