以數值方法分析擋土牆邊坡之降雨排水行為

A Study of Rainfall and Drainage in a Slope with Retaining Wall by Using Numerical Method

林家名(Charming Lin)

指導教授 ： 馮道偉

中原大學/工學院/土木工程學系/碩士(2006年)

https://doi.org/10.6840/cycu200600564

摘要

擋土牆為邊坡穩定主要設施，設計規範中僅以「每兩平方公尺一孔」規定擋土牆排水管數量，並未考慮到土壤性質、降雨入滲、坡頂裂縫對排水效能之影響。本研究之目的在於了解上述變因對擋土牆邊坡降雨入滲排水行為之影響。
本研究以數值程式SEEP/W，針對砂質壤土、粉質粘土及龍潭紅土等三種均質土壤擋土牆邊坡，考慮不同颱風降雨型式、不同坡頂裂縫深度、不同坡頂裂縫與牆背距離、不同排水管間距等四種影響因素，進行降雨入滲排水分析，以了解牆背地下水位高程變化。
本研究之結論如下：（1）在擋土牆底部排水管之高程低於初始牆背水位高程之前提下，設置底部排水管能有效地降低擋土牆背之初始地下水位高程。降雨期間，排水管能延緩牆背水位之上升速度並降低牆背水位之最大上升高度；（2）滲透係數值高之未飽和土壤（如龍潭紅土）擋土牆邊坡若以垂直間距1公尺設置排水管，降低降雨期間之最高牆背水位的效果並不明顯，若增加其排水管直徑則有助於降低最高牆背水位。（3）滲透係數甚低之未飽和土壤（如粉質粘土）擋土牆邊坡由於降雨入滲量極少，只須設置底部排水管即可；（4）未飽和狀態下對應滲透係數愈大之土壤擋土牆邊坡，其牆背水位愈易受降雨型式所影響；（5）坡頂裂縫將導致降雨期間降雨之入滲速度及入滲量大幅提升，越深之裂縫其降雨入滲量越大，牆背水位上升速度及抬升高度皆有顯著增加；但坡頂裂縫距牆背超過6公尺後，其對牆背水位高程之影響已大幅減少。

關鍵字

排水管 ； 降雨入滲排水 ； 擋土牆

並列摘要

Retaining wall is the major slope stability structure. The design standard only controls the number of retaining wall’s drains by “one drain in each 2 m2,” and it dosen’t concern about the effects of soil properity, rainfall infiltration, and cracks. The objective of this study is to understand the effects of these factors on the behavior of rainfall and drainage in a slope with retaining wall.
This study used three types of soils, including sandy loam, silty clay and Lungtan soil in the analysis of rainfall and drainage under different influence factors by using SEEP/W.
The results of this study are as follow: 1) if the level of bottom drains is lower than initial water table level, the bottom drains can decrease the initial water table level effectively; 2) the drains couldn’t decrease the highest water table level behind the wall with high permeability unsaturated soil during rainfall, if setting up the vertical spacing of drains was 1 m. With increasing the diameter of drains, the drains could lower the highest water table level behind the wall; 3) The low permeability unsaturated soil only need to set up bottom drains; 4) the higher is the permeability of unsaturated soils, the easier is the water table influenced by rainfall type; 5) the deeper is the cracks, the higher is the elevation of water table during rainfall; once the distance between cracks and retaining wall is greater than 6 m, the influence of cracks will be reduced greatly.

並列關鍵字

drains ； SEEP/W ； retaining wall ； drainage

參考文獻

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