不同級配砂對邊坡管湧現象之探討

A Study for Piping Phenomenon of the Different Graded Sands on Slope

鄧雍瀚(Yuan-Han Deng)

指導教授 ： 張德鑫

中原大學/工學院/土木工程研究所/碩士(2010年)

https://doi.org/10.6840/cycu201000911

摘要

坡地滲流之水力坡降若超過該地區土壤臨界水力坡降值，則會發生管湧現象，並造成山坡破壞並發生災害。本研究應用陳瀅如(2002)推導之介質孔隙率與滲透係數關係式，並修正王欣雅(2009)推導之邊坡土壤之臨界水力坡降值公式，以不同粒徑之級配砂討論粒徑分佈對臨界水力坡降值影響。
本研究利用管湧邊坡模型試驗，考慮因粒徑不同之級配砂，可得在不同級配砂下之臨界水力坡降值。研究中亦利用FEMWATER數值模式進行管湧試驗之數值模擬，利用模擬所得之水流速度及率定後土體之水力傳導係數，可計算管湧破壞面局部之水力坡降值。
最後本研究比較臨界水力坡降理論、模型試驗及數值模擬值，得知試驗所得之臨界水力坡降值小於理論及數值模擬分析值，主要為試驗數據兩測壓管間所得之區域平均水力坡降值，而理論值與數值模擬值則為坡面局部之水力坡降值，且兩者甚為接近。最後，本研究發現粒徑參數比D*與臨界水力坡降值有一關係，其值為0.50~0.80之間。經比較， D*近似於實驗砂樣之均勻係數Cu之倒數值。因此根據級配砂之粒徑分佈、物理性質及邊坡角度即可推估級配材質邊坡之臨界水力坡降近值。

關鍵字

級配砂 ； 管湧

並列摘要

If the hydraulic gradient which caused by the underground seepage of mountain slope was greater than the critical hydraulic gradient of this area, the piping phenomenon occurs and which leads to a huge amount of damage. This study applied Chen’s (2002) formula and corrected Wang’s (2009) formula in order to discuss the effect of the critical hydraulic gradient by particle size distribution. The materials of particle size are with different size Graded sand.
This study obtained the critical hydraulic gradient in different particle size Graded sand by experimental model. The model was used by heterogeneous layered piping phenomenon. In this study, the simulation of heterogeneous piping phenomenon used FEMWATER, a commercial soft ware of Finite Element Method simulation. We simulated according to the results of experiments, such as soil properties and boundary conditions, and use the results of simulations, i.e. the velocity of seepage and hydraulic conductivity, to calculate critical hydraulic gradient.
From the comparison among analytical solution, experimental result and FEM simulation, the critical hydraulic gradient of experiment was less than the results from numerical simulation. This study found a relationship between hydraulic gradient, and particle size ratio D* value, which was between 0.50 ~ 0.80. By comparison, D* approximated the reciprocal of the uniform coefficient value Cu.Therefore, slope of the graded material close to the critical hydraulic gradient value can be estimated according to particle size distribution, physical properties and the slope angle.

並列關鍵字

piping

參考文獻

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[23] 林繼立(2005)，「坡地裂縫位置對邊坡穩定之影響」，私立中原大學土木工程學系碩士論文，P.34-55。

[32] 王欣雅(2009) 「非均質邊坡管湧現象之探討」，私立中原大學土木工程學系碩士論文，P.20-34。

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