山區林道挖方邊坡背拉式擋土排樁穩定工法力學參數研究

Mechanical Parameter Study of Tied-Back Retaining Pile Stabilization Method for Cut Slopes of Forest Roads in Mountain Areas

林德貴(Der-Guay Lin) ； 王勝賢(Sheng-Hsien Wang) ； 張國欽(Kuo-Chin Chang) ； 陳威翔(Wei-Hsiang Chen)

《中華水土保持學報》 47卷3期 (2016/09) Pp. 135-146

https://doi.org/10.29417/JCSWC.201609_47(3).0003

摘要

本研究針對宜專一線公路地滑區與背拉式地錨擋土排樁之監測結果，進行三維有限元素數值分析。同時，設置崩積層－均質邊坡及崩積層／岩層－異質邊坡，進行排樁及地錨參數研究。在數值模型中，選用地錨錨碇段長度L_g及傾角θ，以及排樁打設間距比S/D等參數，探討其對邊坡穩定性及排樁結構力學行為之影響。依據分析成果，排樁在崩積層／岩層－異質邊坡之穩定性安全係數FS，皆高於崩積層－均質邊坡者，此說明排樁樁尖貫入承載層之重要性。當排樁打設間距比S/D=6至8時，FS幾無變化；但當S/D=8至10時，FS會明顯降低。此乃由於排樁打設間距超過8倍樁徑後，排樁間之土拱效應消失所致。再者，當地錨之錨碇段長度為5至7 m時，崩積層－均質邊坡之FS明顯上升，而崩積層／岩層－異質邊坡之FS則微幅提升；而錨碇段長度為7至10 m時，兩者之FS皆趨於定值。

關鍵字

三維有限元素數值分析 ； 背拉式擋土排樁 ； 錨碇段長度 ； 穩定性安全係數

並列摘要

This study performed a series of three-dimensional (3-D) finite element analyses to investigate the stabilization mechanism of the tied-back retaining pile installed at the Yi-Zhuan-No.1 Landslide. Meanwhile, a homogeneous slope of colluviums and heterogeneous slope of colluviums with bedrock underneath, were established to perform a systematic numerical experiment on various design parameters of the tie-back retaining pile. In numerical experiments, the design parameters consist of the anchorage length (L_g), inclination (θ) and the spacing ratio (S/D =pile spacing/pile diameter) of retaining pile. According to the numerical experiments, the FS value of a heterogeneous slope is always higher than that of a homogeneous slope and this demonstrates the importance of penetrating the retaining pile into the bedrock (bearing stratum) in the design. Moreover, the FS value greatly decreases as the installation spacing S value surpasses 8D (S ≥ 8D) and this indicates that the arching effect between two adjacent piles immediately disappears when the spacing of piles is larger than 8 times of pile diameter. In addition, the FS value of homogeneous slope is greatly promoted when the anchorage length L_g increase from 5 to 7 m while it is not the case for heterogeneous slope the increase is very rare. However, the FS values of the two types of fictitious slopes, become unchanged and tend to a constant when the L_g value increases from 7 to 10 m.

並列關鍵字

Three-dimensional (3-D) finite element analyses ； Tied-back retaining pile ； Anchorage length ； Factor safety of slope stability