Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/89368
標題: Seepage-induced stability and mechanical analyses of slopes stabilized using tied-back retaining piles under rainfall conditions
降雨條件下背拉式排樁整治邊坡之滲流穩定性及力學分析
作者: 陳家棟
Jia-Dong Chen
關鍵字: 降雨入滲
飽和度
孔隙水壓
背拉式擋土排樁
打設間距
排樁長度
錨碇段長度
入岩深度比
穩定性安全係數
rainfall infiltration
degree of saturation
pore water pressure
tie-back retaining pile
installation spacing
pile length
anchorage length
bedrock penetration ratio
factor of safety (FS value)
引用: 參考文獻 1. Akira, A., Toshihisa, A., Fusao, O. 1997. Deformation and Progressive Failure in Geomechanics. 2. Brooks, R.H. and Corey, A.T. 1964. Properties of porous media affesting fluid flow. J. Irrig. Drain. Div. Am.Soc.Civ. Eng, Vol 92(IR2), pp. 61-88, 3. Brutsaert, W. 1966. Probability laws for pore size distribution. Soil Sci. Soc. Am. J., Vol 101, pp. 85-92. 4. Cai, F. and Ugai, K. 2000. Numerical analysis of the stability of a slope reinforced with piles. Soils and Foundations, 40(1), pp. 73-84. 5. Chen, C.Y. and Martin, G.R. 2002. Soil-structure interaction for landslide stabilizing piles, Computers and Geotechnics, Elsevier, No.29, pp. 363-386. 6. Duncan, J.M and Wright, S.G. 1996. Soil Strength and Slope Stability. John Wiley and Sons, Inc., 297p. 7. Das, B.M. 2007. Principles of Foundation Engineering, 6th ed. Thomson Canada, Ltd., 445p. 8. Fredlund, D. G., Morgenstern, N. R. and Widger, R. A. 1978. The Shear Strength of Unsaturated Soil. Canadian Geotechnical Journal, Vol. 15, No.3, pp. 313–321. 9. Fleming ,W.G.K., Weltman ,A.J., Randolph, M.F. and Elson,W.K. 1985. Piling Engineering. pp.183~216. 10. Fredlund, D. G., and Rahardjo, H. 1993. Soil mechanics for unsaturated soils. New York, N.Y.: Wiley. 11. Garner, W.R. and Mayhugh, M.S. 1958. Solutions and tests of the diffusion equation for the movement of water in soil. Soil Sci. Soc. Am. J., Vpl 22, pp. 197-201. 12. Ghaly, A., Hanna, A. and Hanna, M. 1991. Uplift Behavior of Screw Anchors in Sand. I: Dry Sand. Journal of Geotechnical Engineering Division, ASCE, Vol. 117, No. 5, pp. 773~793. 13. Gottardi, G. and Venutelli, M. 1993. Richards: computer program for the numerical simulation of one-dimensional infiltration into unsaturated soil. Computers and Geosciences, Vol 19, pp. 1239-1266. 14. Geddes, J. D., and Murray, E. J. 1996. Plate Anchor Groups Pulled Vertically in Sand. Journal of Geotechnical Engineering, ASCE, Vol. 122, No. 7, pp.509~516. 15. Geotechnical engineering office. 1984. Geotechnical manual for slopes. 16. Graham, R.S., Oberlander, E.K., Stewart, J.E. et al. 2000. Validation and use of a finite element model of C-2 for determination of stress and fracture patterns of anterior odontoid loads. J Neurosurg,93:17-125 17. Hanna, T. H. 1982 Foundation in Tension Ground Anchors. McGraw-Hill Book Company, New York. 18. Hillel, D. 1980. Fundamentals of soil physics. Academic Press, Inc.(London) Ltd. 19. Khazai, B. and Sitar, N. 2000. Assessment of Seismic Slope Stability Using GIS Modeling. Geographic Information Sciences, 6(2), pp.121-128. 20. Larnach, W. J. and McMullan, D. J. 1973. Behaviour of Inclined Groups of Plate Anchors in Dry Sand. Proceeding Conference Institution of Civil Engineering London, England, pp. 153~156. 21. Lumb, P. 1975. Slope Failures in Hong Kong. Quarterly Journal Engineering Geology,Vol.8, pp.31-65. 22. Lee, W. A., Thomas, S. L., Sunil, S.and Glenn M. B. 2001 Slope Stability and Stabilization Methods Hardcover, November 1, 23. Meyerhof, G. G. and Adams J. I. 1968. The Ultimate Uplift Capacity of Foundations. Canadian Geotechnical Journal, Vol. 5, pp. 225~244. 24. Mualem, Y. 1978. A New Model for Predicting the Hydraulic Conductivity of Unsaturated porous media. Water Resource. Res., Vol. 12, No. 3, pp.513–522. 25. Moriwaki, H., Inokuchi, T., Hattanji, T., Sassa, K., Ochiai, H. and Wang, G. 2004. Failure Processes in a Full-Scale Landslide Experiment Using a Rainfall Simulator. Landslides, Vol. 1, No.4, pp. 277–288. 26. Mohamed, A. and Hamed, A. 2012. P–y curve and lateral response of piles in fully liquefied sands. Canadian Geotechnical Journal, 49(6), 633-650, 27. Poulos, H. G. 1973. Analysis of piles in soils undergoing lateral movements. Journal of the Soil Mechanics and Foundations Division SM5, ASCE, Vo l. 99, pp. 391-406. 28. Poulos, H. G., Chen, L. T., and Hull, T. S. 1997. Model tests on pile groups subjected to lateral soil movement. Soils and Foundations, Vol. 37, No. 1, pp. 1-12. 29. Reese, L.C., Wang, S.T., and Fouse, J.L. 1992. Use of drilled shafts in stabilizing a slope. Stability and Performance of Slopes and Embankments: II, Geotechnical Special Publication 31,ASCE, Vol.2, pp.1318-1322. 30. Russo, D. 1998. Determining soil hydraulic properties by parameter estimation: on the selection of a model for the hydraulic properties. Water Resour.Res., Vol 24, 3 , pp. 453-459. 31. Rahardjo, H., Leong, E.C., and Rezaur, R.B. 2001. Instrumented slopes for the study of rain-induced slope failures. Proceedings Of the 14th Southest Asian Geotechnical Conferences , Hong Kong, 10-14 December, Vol. 3. 32. Skempton A.W. 1969. Long Term Stability of Clay Slopes. 4th Ranking Lecture, Geotechnique, 1412:7-102. 33. Su, W. and Fragaszy, R. J. 1988. Uplift Testing of Model Anchors. Journal of Geotechnical Engineering Division, ASCE, Vol. 114, No. 9, pp. 961~983. 34. Smethurst, J. A. and Powrie, W. 2007. Monitoring and analysis of the bending behaviour of discrete piles used to stabilise a railway embankment. Geotechnique 57, No. 8, 663–677 35. Terzaghi, K. and Peck, R.B. 1967. Soil Mechanics in Engineering Practice. 2ed John Wiley & Sons, Inc., 729p. 36. Tomio Ito, Tamotsu Matsui. 1975. Method to estimate lateral force acting on stabilizing pile.' Journal of Japanese Society of Soil Mechanics and Foundation Engineering, 15(4): 43 – 59. 37. Tyler, S.W. and Wheatcraft., S.W. 1989. Application of fractal mathematics to soil water retention estimation. Soil Sci. Soc. Am. J., Vol 59, pp. 987–996. 38. Turner, J. P. and Kullhawy, F. H. 1990 Drained Uplift Capacity of Drilled Shafts under Repeated Axial Loading. Journal of Geotechnical Engineering Division, ASCE, Vol. 116, No. 3, pp. 470~491. 39. Van Genuchten, M. T. 1980. A Closed-Form Equation for Predicting the Hydraulic Conductivity of Unsaturated Soils. Soil Science Society of America Journal, Vol. 44, pp. 892–898. 40. Van Genuchten, M.T. and Nielsen, D.R. 1985. On describing and predicting the hydraulic properties of unsaturated soils. Ann. Geophysica, Vol 3, pp. 615–628. 41. Wiseman, R. J. 1966. Uplift resistance of groups of bulbous piles in sand. MSc thesis, Nova Scotia Technical College. 42. Wei, W. B. and Cheng, Y. M. 2009. Strength reduction analysis for slope reinforced by piles, Computers and Geotechnics, 36(7), pp.1176–1185. 43. 姜禮應(1981),「地下水對斜面破壞之模型試驗」,國立中興大學水土保持研究所,碩士學位論文。 44. 張萬芳(1982),「地下水位與傾斜角對邊坡破壞之效應研究」,國立中興大學水土保持研究所,碩士學位論文。 45. 歐晉德(1987),Q與A專欄,地工技術雜誌,第17 期,第85 頁。 46. 李建中、姚錫齡、徐乃平、施並淵(1989),「地錨在台北沉泥質土層中之力學行為」,中華民國第三屆大地工程學術研討會論文集,第659~670 頁。 47. 台灣省政府山地農牧局(1989),「台灣省崩塌地調查報告」,農委會山地工作報告,24(2):110-139。 48. 張光甫(1990),「擴座地錨在砂土中錨碇行為之模型研究」,國立台灣工業技術學院,碩士學位論文。 49. 日本道路公團(1992),「土質地質調查要領」。 50. 廖洪鈞(1992),「砂土中單段錨碇端受力行為和群錨行為之研究」,國科會專題研究報告。 51. 許世宗(1995),「砂土中垂直地錨之錨碇行為」,國立台灣工業技術學院,博士學位論文。 52. 李明慶(1998),「多段錨碇式地錨之拉拔力-位移關係」,朝陽科技大學營建工程系,碩士學位論文。 53. 廖洪鈞、張光甫(1998),「地錨設計與施工規範之探討」,地工技術雜誌,第 70 期,第75~91頁。 54. 行政院內政部建築研究所(1998),建築技術規則建築構造編基礎構造設計規範(含解說)。 55. 內政部營建署營建自動化專案計畫報告(1999),「坡地社區開發安全監測手 冊」。 56. 賴振輝、許海龍(1999),「地下水位升降與坡頂加載對崩塌後邊坡穩定性之影響」,第八屆大地工程學術研討會。 57. 蔡承恩(1999),「砂土中錐型擴座地錨荷重-位移關係之預測模式」,朝陽科技大學營建工程系,碩士學位論文。 58. 行政院勞工委員會勞工安全衛生研究所(2000),施工安全技術手冊。 59. 李振誥、陳尉平、李如晃(2001),「應用基流資料估計法推估台灣地下水補注量」,台灣水利,50: 69-80 60. 行政院內政部營建署(2001),建築物基礎構造設計規範。 61. 中國土木水利工程學會(2001),「地錨設計與施工準則暨解說」,第三版,科技圖書有限公司。 62. 李春友、任理、李保國(2001),「利用優化方法求算Van Genuchten 方程參數」,水科學進展,第12卷,第4 期,第473-478頁。 63. 廖瑞堂(2001),山坡地護坡工程設計,科技圖書股份有限公司。 64. 石棟鑫(2001),「台灣地區颱風雨降雨型態之分析研究」,中央大學土木工程研究所,碩士論文。 65. 洪如江、林美聆、陳天健、王國隆(2000),「921 集集大地震相關的坡地災害坡地破壞特性與案例分析」,地工技術,Vol 81, pp.17-31。 66. 陳肇成(2002),「土壤邊坡穩定數值分析方法之研究」,國立中興大學土木研究所,碩士學位論文。 67. 陳進發(2002),「未飽和層土壤水平衡模式解析及其應用之研究」,國立成功大學資源工程學系,博士學位論文。 68. 范嘉程、馮道偉(2003),「以有限元素法探討暴雨時邊坡之穩定分析」,地工技術,第95期,第61-74頁。 69. 行政院農業委員會水土保持局(2003),「水土保持技術規範」 70. 交通部中央氣象局(2004),雨量分級定義 71. 倪至寬(2004),「基礎施工與品管」,詹式書局, 461頁。 72. 莊棓景(2004),「沉泥質砂土中傾斜錐形擴座地錨之三向度分析」,朝陽科技大學,碩士學位論文。 73. 何思漢(2004),「砂土中垂直擴座群錨之受力行為」,朝陽科技大學營建工程系,碩士學位論文。 74. 呂明杰(2004),「土壤邊坡降雨入滲行為之探討」,私立中原大學土木工程研究所碩士學位論文。 75. 何仁溫(2005),「沉泥質砂土中傾斜承拉式摩擦型地錨之三向度分析」,朝陽科技大學,碩士學位論文。 76. 蔡和倫(2010),「邊坡入滲與土體位移行為研究之大型試驗」,國立屏東科技大學水土保持系,碩士學位論文。 77. 張睦雄、張俊隆、陳建華、蔡衛勇、蔡宗成(2010),「公路邊坡抗滑排樁現地土壓力之量測與判釋」,臺灣公路工程,第36卷,第1期。 78. 行政院農委會林務局(2011),「林道邊坡損壞類型調查、監測、檢測及治理工法研究」,第一次期中報告,晟太工程顧問公司執行。 79. 林煥軒(2011),「高屏溪集水區土砂災害降雨特性之研究-以莫拉克颱風為例」,國立屏東科技大學水土保持學系,碩士論文。 80. 許建裕、周延聲(2012),「預壘椿工法」,水利土木科技資訊,第55 期,第46-49頁。 81. 行政院農委會水土保持局(2012),水土保持相關法規彙編,水土保持技術規範。 82. 邱倍堅(2012),「擋土止滑排樁穩定邊坡之力學行為三維數值分析」,國立中興大學水土保持學系,碩士學位論文。 83. 曾仁郁(2013),「不飽和土壤水份特徵曲線特性及土壤初始水頭對邊坡穩定之影響」,國立高雄第一科技大學營建工程研究所,碩士學位論文。 84. 林韋君(2013),「山區道路邊坡背拉式擋土排樁之穩定機制研究」,國立中興大學水土保持學系,碩士學位論文。 85. 莊欣蓉(2014),「未飽和自然邊坡於降雨及地震情況下之滲流與穩定分析」,國立中興大學水土保持學系,碩士學位論文。
摘要: 本研究首先採用前人完成之室內大型人工邊坡降雨入滲試驗監測資料,進行三維有限元素數值模擬比對,以檢核降雨強度對邊坡滲透性之影響。另外,參用英國Hildenborough區之鐵路邊坡堤防整治成果及傾斜管監測結果,進行三維數值模擬,以探討現地擋土排樁之穩定機制,並比對傾斜管變位及排樁彎矩模擬值與現場監測值之吻合度,以驗證數值模擬程序之有效性。 隨之,設置一組崩積層-均質邊坡,並針對各類水力數值變數進行降雨入滲參數研究,以檢核水力數值變數在降雨期間,對邊坡飽和度S(%)、孔隙水壓Pwater、以及穩定性之影響。參數研究中,所採用之水力數值變數包括:不同初始地下水水位(hwo)、不同設計雨型、以及不同水力傳導係數函數kr(ψ)~(ψ)。 同時,各建立ㄧ組崩積層/岩層-異質邊坡及崩積層-均質邊坡,並針對背拉式擋土排樁之各項設計參數進行數值試驗,以測試其對邊坡穩定性及背拉式擋土排樁結構力學行為之影響。數值試驗中,所採用之擋土排樁設計參數包括: 邊坡坡度(βº)、排樁打設長度(Lp)、打設間距(S/D)、地錨錨碇段長度(Lg)、地錨傾角(θ)及地錨極限拉力(Ta)。 最後,於施設背拉式擋土排樁穩定工法之均質邊坡,進行降雨入滲分析,以便探討在降雨期間,施設穩定工法對邊坡穩定機制之影響。同時,藉由數值試驗中,來檢視在不同初始地下水水位(hwo)、以及不同設計雨型條件下,穩定工法對邊坡穩定性之貢獻度。 率定驗證現況模擬部份,室內人工邊坡降雨入滲試驗之模擬結果顯示,降雨期間邊坡土體之飽和度及孔隙水壓模擬值變化趨勢,與試驗量測值相當吻合。另者,在鐵路邊坡堤防擋土排樁整治之模擬結果顯示,其傾斜管位移量與排樁彎矩之模擬值與現地量測值也相當吻合。 在崩積層-均質邊坡降雨入滲分析部份,由數值試驗結果可知: (1) 在同一降雨延時條件下,初始地下水水位較高時,邊坡之FS値也相對偏低(高水位hwo=1.5 m → 低水位hwo=5.5 m,FS=0.9927→1.089)。在高水位情況下,邊坡潛在滑動面主要發展於上邊坡區域。 (2) 在同一降雨延時條件下,前鋒型降雨情況,邊坡之FS値也相對偏低(後鋒型降雨→前鋒型降雨,FS=1.091→1.049),且其潛在滑動面主要發展於上邊坡區域。 (3) 降雨期間,基質吸力提高時(ψ→1.5ψ)土壤之保水性較佳,土壤中之孔隙水壓不會隨著降雨末期降雨強度大幅減緩,而逐漸消散。此結果將導致邊坡之抗滑能力降低,而穩定性安全係數FS値隨之降低(0.5ψ→1.5ψ,FS=1.109→1.075)。同時,邊坡潛在滑動面主要發展於上邊坡區域。 由崩積層-均質邊坡施設背拉式擋土排樁之數值試驗結果可知: (1) 在邊坡坡度固定之情況下(β=35°),當提高地錨極限拉力時(Ta=40→50→60 t),Ta對邊坡穩定性影響極微小。因此,未考慮邊坡坡度,而只藉由增加地錨極限拉力來提升邊坡穩定性,其效果有限。反之,在邊坡坡度不同之情況下,Ta對邊坡穩定性之影響程度也不同。另外,在邊坡坡度β (=35°)固定,而地錨傾角θ=30°時,FS值可達最大値 (θ以10°增量來改變;θ=10°~40°)。此乃由於β≡θ所致。 (2) 在各種打設間距(S/D=間距/樁徑=4~8)條件下,若將排樁打設長度(Lp=6、9、12 m)加深,則FS值隨之增加。施設地錨之後能縮小滑動面發展之範圍,進而有效提升擋土排樁之抗滑能力。 (3) 若排樁打設間距增加,FS值將逐漸減小,且當打設間距S/D=8時,FS值將大幅下降。 (4) 在固定地錨總長度之情況下,逐漸增加地錨之錨碇段長度(Lg),雖FS值亦會隨之提升,但終將趨於定值。 另外,由異質邊坡之背拉式擋土排樁數值試驗結果可知: (1) 由於崩積層厚度較小,潛在滑動面被侷限於崩積層而不向下發展進入岩層。由於滑動面都落於崩積層與岩層交界面,其深度變化微小,使得排樁入岩深度比Rr(=Lpr/Lpc其中,Lpr=排樁之入岩深度,Lpa=排樁之崩積層貫穿厚度)對FS值幾乎不影響。當排樁入岩深度比Rr 由3增加為5時,兩者之排樁樁身撓曲曲率M/EI及剪力分布將趨於一致。 (2) 在排樁入岩深度比Rr =1之情況下,若提高排樁打設間距:S=4D→8D,FS值將逐漸減少,且當S=8D時,其FS值將達最小値。 (3) 在固定地錨總長度之情況下,逐漸增加地錨之錨碇段長度(Lg),FS值亦會隨之提升,但終將趨於定值。 最後,由均質邊坡施設背拉式擋土排樁穩定工法,進行降雨入滲數值試驗結果可知: (1) 在不同初始地下水水位或設計雨型條件下,隨著降雨延時增長,邊坡之安全係數FS皆有下降之趨勢。而在相同降雨延時條件下,於高水位或前峰型降雨之情況,邊坡之穩定性安全係數最小。 (2) 在降雨入滲分析中,邊坡施設穩定工法之穩定性安全係數皆高於未施設者。但在初始下地水水位過高或前峰型降雨情況下,穩定工法對邊坡安全係數之提升效果將會受到折減。 (3) 在降雨入滲分析中,施設穩定工法之邊坡,土體承受降雨所產生之位移,較未施設穩定工法者明顯減少,且隨降雨延時增加,排樁樁身之彎矩及剪力亦隨之增加。
Firstly, this study performed a three-dimensional (3-D) finite element analysis to simulate a large scale man-made slope subjected to artificial rainfall in laboratory to inspect the effect of rainfall intensity on the infiltration and seepage behaviors of the slope. In addition, using the inclinometer monitoring data of a railway embankment at Hildenborough, U.K., this study carried out a 3-D numerical simulation to investigate the stabilization mechanism of retaining piles. Comparing the lateral displacement and bending moment of retaining piles from simulation with those from measurement, one can verify the validities of the numerical procedures and material model parameters used in the simulation. Subsequently, a model slope consists of colluviums (called homogeneous slope) was set up for carrying out a series of rainfall induced seepage analyses and parametric studies on various hydraulic numerical variables to investigate their effects on the degree of saturation S(%), pore water pressure Pwater, and slope stability during rainfall. The numerical variables adopted in parametric studies include: initial groundwater level (hwo), design rainfall pattern, and hydraulic conductivity function kr(ψ)~(ψ). In which, the variable ψ denotes the pressure head of groundwater (ψ ≧ 0 → suction force, ψ< 0 → squeeze force). Meanwhile, a model slope comprises colluviums and bedrock (called heterogeneous slope) was constructed for performing a systematic numerical experiments on various design parameters of Tie-Back Retaining Pile (TBRP). The effects of design parameters on the slope stability and mechanical behaviors of tie-back retaining pile were examined. In numerical experiments, the numerical variables consist of material and geometry types encompass: the slope angle (βº), pile length (Lp), pile spacing ratio (S/D=pile spacing/pile diameter), anchorage length (Lg), inclination angle of anchor (θ), and ultimate tension of anchor (Ta). At last, a rainfall induced seepage analysis was performed on a homogeneous slope stabilized by TBRP to investigate the stabilization mechanism during rainfall. At the meantime, through the numerical experiments, the contribution of TBRP to the slope stability under different initial groundwater levels (hwo) and design rainfalls was inspected. For calibrated and verified simulations, the numerical results of artificial rainfall induced seepage analyses on a large scale man-made slope indicate that the variation trends of degree of saturation S (%) and pore water pressure of simulation are in excellent agreement with those of measurement. Moreover, the numerical results of railway embankment stabilized by retaining piles demonstrate that the lateral displacement and bending moment of pile shaft from simulations are fairly coincident with those from observations. Based on the numerical experiments of rainfall induced seepage analyses for a homogeneous slope without TBRP, several conclusions are made: (1) For a specific duration of rainfall, the FS value tends to be lower when the initial groundwater level becomes higher. For example, a high groundwater level hwo=1.5 m → low groundwater level hwo=5.5 m, the factor of safety FS=0.993→1.089. Under a high groundwater level situation, the potential sliding surfaces are mainly mobilized at the area of upslope. (2) For a designated duration of rainfall, the FS value of the slope is relatively low for a pre-peak type rainfall (post-peak type rainfall→pre-peak type rainfall, FS=1.091 → 1.049). The potential sliding surfaces is mainly developed at the upslope zone. (3) According to the numerical results, for a slope with higher matric suction (ψ →1.5ψ) reveals that the soil mass possesses a higher capability to conserve the infiltrated rain water during rainfall and certain amount of pore water pressure remains at the end of rainfall duration when rainfall intensity largely decreases. However, these lead to a reduction of shear resistance and decrease of the factor of safety FS (FS=1.109→1.075 for 0.5ψ → 1.5ψ) of the slope. At the meantime, the potential sliding surface is mainly mobilized at the upslope area. According to the numerical results of a homogeneous slope stabilized by TBRP, following conclusions can be drawn: (1) For a slope with specific gradient (or slope angle β=35°), the increase of the ultimate tension of anchor Ta (Ta=40→50→60 ton) only shows a negligible effect on the slope stability. As a result, it is limited to promote the slope stability simply by increasing the ultimate tension of anchor without considering the gradient of the slope. The influence extent of Ta on the slope stability is dependent on the gradient of the slope. In general, the FS value turns to be a maximum if the installation angle of anchor θ approximates the slope angle β (β≡θ). For a case of β=35°, based on the numerical experiment on θ=10°~40° with increment of 10°, it is found that a maximum FS value can be obtained for θ=30°. (2) For a slope with specific installation spacing of TBRP (S/D=spacing/pile diameter=4~8), the FS value increases with the increasing pile length (Lp=6 、 9、 12 m). In addition, the installation of tied-back anchor enables to restrain the potential sliding surface in a smaller range and it alternately promotes the shear resistance of retaining pile. (3) The FS value decreases with the increasing installation spacing of TBRP and eventually a remarkable decrease of FS value occurs as the installation spacing S equals to eight times of pile diameter (S = 8D). (4) For a slope with specific total length of anchor, although the FS value increases with the increasing anchorage length (Lg), it eventually tends to be a constant. In addition, based on the numerical experiments of a heterogeneous slope stabilized by TBRP, some conclusions are summarized as follows: (1) Due to the thin thickness of colluvium, the potential sliding surface is always restrained within colluvium zone or near the soil/bedrock interface and it unable to penetrate into the underlying bedrock. As a consequence, the bedrock penetration depth ratio Rr (=Lpr/Lpc=penetration depth of bedrock/penetration depth of colluviums) of retaining pile almost has no effect on the FS value. The distributions of bending curvature M/EI and shearing force of pile shaft tend to be identical as the Rr ratio increases from 3 to 5. (2) For a bedrock penetration ratio of retaining pile Rr =1, the FS value decreases with the increasing installation spacing S (=4D → 8D) and it turns to be a minimum as the installation spacing S equals to eight times of pile diameter (S=8D). (3) For a case of S/D=6 and Rr=1, the FS value increases with the increasing anchorage length (Lg), however, the FS value eventually tends to be a constant. At last, based on the numerical experiments of rainfall induced seepage analyses on a homogeneous slope stabilized by TBRP, following conclusions can be drawn: (1) For different initial groundwater level and design rainfall, the FS value constantly tends to descend with the extension of rainfall duration. For a specific rainfall duration, a slope with high groundwater level and subjected to pre-peak type rainfall always lead to a lowest factor of safety. (2) The FS value of homogeneous slope with TBRP is constantly higher than that without TBRP during rainfall. However, under a high initial groundwater level and pre-peak type rainfall situations, the promotion of FS value contributed by TBRP will be largely deducted. (3) The rainfall induced displacement of a homogeneous slope with TBRP is significantly smaller than that without TBRP. Meanwhile, the bending moment and shearing force of pile shaft increase with the extension of rainfall duration.
URI: http://hdl.handle.net/11455/89368
其他識別: U0005-1408201516381200
文章公開時間: 2018-08-18
Appears in Collections:水土保持學系

文件中的檔案:

取得全文請前往華藝線上圖書館



Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.