柱狀改良樁對底部抗隆起安全係數的影響

EFFECT OF GROUT PILES ON FACTOR OF SAFETY AGAINST BASAL HEAVE

10.6652/JoCICHE.201806_30(2).0007

蘇世豐(Shi-Fon Su)

底部隆起 ； 深開挖 ； 黏土和柱狀改良加勁黏土 ； basal heave ； deep excavation ； clay, and clay reinforced with grout piles

中國土木水利工程學刊

30卷2期（2018 / 06 / 01）

151 - 162

繁體中文

目前的圓弧滑動分析法，並沒有針對柱狀式改良樁加勁黏土地盤，發展出合適的開挖底部穩定分析模式。由於滑動面通過黏土與柱狀改良加勁黏土，其動員的剪力強度反應是有所差異，所以本研究選用兩個近似的強度值來代表不同滑動區的強度動員，分別是平均動員於開挖區外側的黏土軸向壓縮強度，以及平均動員於開挖區內側的柱狀改良加勁黏土軸向伸張強度。當結合擋土結構之深度修正係數，則可建立修正型的圓弧滑動分析法，並可評估開挖底部之不排水穩定性，經由波士頓數值開挖結果和四個現場案例的比較，証實建議分析法的合適性。當改良率愈大則改良樁的強度動員愈大，且改良後的底部抗隆起安全係數增量亦是愈大，而改良率所引致的底部抗隆起安全係數增量，兩者約略是呈1:1.4～1:2.4的關係。

The circular slip method has not been specifically developed for the base stability analysis of a grout pile reinforced excavation in clay. To deal with the influence of mobilized strengths of clay and clay reinforced with grout piles on the failure slip surface, two approximate strength values of axial compression strength of clay and axial extension strength of clay reinforced with grout piles are used in the isotropic slip analysis to represent the average shear resistance mobilized on failure planes outside and inside the excavation, respectively. After combining a factor correcting for the depth of the excavation wall, a modified circular slip method can be established. The suitability of the proposed method for analyzing the base stability of deep excavations is verified by comparing with the numerical study results of deep excavations in Boston and four field cases. Generally, the larger the ground improvement rate, the more the material strength of grout pile can be mobilized. The increase rate of factor of safety becomes larger when the ground improvement rate is higher. But the factor of safety becomes insensitive to the undrained shear strength of grout pile when the improvement ratio is less than 10%. This result is found that the increment of factor of safety against base heave and the increment of improvement ratio is generally in a ratio from 1:1.4 to 1:2.4.

1. Architectural Institute of Japan(1988).Recommendations for Design and construction practice of earth retaining for excavation.Tokyo:
2. Bjerrum, L.,Eide, O.(1956).Stability of strutted excavations in clay.Geotechnique,6(1),32-47.
3. Clough, G. W.,Hansen, L. A.(1981).Clay anisotropy and braced wall behavior.Journal of the Geotechnical Engineering Division, ASCE,107(7),893-913.
4. Finno, R. J.,Nerby, S. M.(1989).Saturated clay response during braced cut construction.Journal of Geotechnical Engineering, ASCE,115(8),1065-1084.
5. Hashash, Y. M. A.,Whittle, A. J.(1996).Ground movement prediction for deep excavations in soft clay.Journal of Geotechnical Engineering, ASCE,122(6),474-486.
6. Ladd, C. C.(1991).Stability evaluation during staged construction.Journal of Geotechnical Engineering, ASCE,117(4),540-615.
7. Liao, H. J.,Su, S. F.(2012).Base stability of grout piles reinforced excavations in soft clay.Journal of Geotechnical and Geoenvionmental Engineering, ASCE,138(2),184-192.
8. O'Rourke, T. D.(1992).Base stability and ground movement prediction for excavations in soft clay.Proceeding ICE Conf. on Retaining Structure,London, England:
9. Su, S. F.(2009).Anisotropic strength evaluation of clay reinforced with grout piles.Journal of Geotechnical and Geoenvironmental Engineering, ASCE,135(10),1529-1537.
10. Su, S. F.,Liao, H. J.(2018).Base stability of deep excavation in clay reinforced with grout piles.Proceedings of the Institution of Civil Engineers-Ground Improvement,171(1),2-11.
11. Su, S. F.,Liao, H. J.,Lin, Y. H.(1998).Base stability of deep excavation in anisotropic soft clay.Journal of Geotechnical and Geoenvironmental Engineering, ASCE,124(9),809-819.
12. Terzaghi, K., Theoretical Soil Mechanics, John Wiley and Sons, New York (1943).
13. 中華民國建築學會，「基礎構造設計規範」，台北 (1988)。
14. 吳宗憲(1994)。台北，國立臺灣工業技術學院。
15. 張惠文,陳福成,陳國隆(1989)。深層攪拌複合地盤之剪力強度特性。第三屆大地工程學術研討會論文集，墾丁:
16. 陳文洲(2004)。台北，國立臺灣科技大學。
17. 廖洪鈞(1998)。國科會專題研究報告國科會專題研究報告,台北:國科會。
18. 蘇世豐,廖洪鈞,林耀煌(1999)。以滑動分析法探討異向性粘土中之深開挖底部抗隆起安全係數。中國土木水利工程學刊，11(2)，259-266。
19. 龔東慶(1997)。台北，國立臺灣科技大學。

1. 蘇世豐(2021)。黏土層之深開挖內擠穩定。中國土木水利工程學刊，33(6)，429-437。
2. (2024)。加勁黏土之深開挖內擠穩定。中國土木水利工程學刊，36(3)，233-242。