臺灣博碩士論文加值系統

本研究以固定開挖底部穩定係數(Nb= H/su)之觀念，利用降低土壤不排水剪力強度，來處理因縮小試驗模型尺寸對開挖底部隆起行為之影響問題，以利模擬粘土層中開挖底部解壓所引致之隆起行為，並利用落錐試驗來控制試驗土壤之不排水剪力強度大小。試驗結果顯示，當粘土強度為定值，且不隨深度增加時，一旦底部隆起產生，則不論擋土壁貫入深淺，其隆起滑動之區域範圍都超過擋土壁底端，並向下沿伸。反之，當模擬粘土強度隨深度增加時，若開挖底部發生隆起滑動，則其滑動範圍皆接近擋土壁底端。就前者可言，由於擋土壁位於滑動範圍內，故增加擋土壁之貫入深度對於抵抗隆起之效果有限。而就後者而言，增加開挖底部土壤之不排水剪力強度對於抵抗隆起有相當明顯的效果，且此時試體之破壞機制較接近一般開挖底部隆起公式之假設，在計算其安全係數後，可以發現隆起量及壁體變形量都有隨著安全係數增加而逐漸減小的趨勢。總之，試驗結果證明本研究所發展之試驗模型，對於軟弱粘土層底部隆起行為之研究，將是有效之工具。

By keeping a constant stability number (Nb= H / Su) for base stability of excavation, the effect of reduced model size on the behavior of base heave can be compensated by reducing the strength of soil. Based on this concept, a model test apparatus has been developed in this research to study the base heave behavior of excavations in soft clay. To control the strength clay to a predetermined value, a fall cone test device is used in this study. When base heave occurs, it has been observed that base heave resulted sliding zone may extend well below the bottom of excavation wall for soil with a constant undrained shear strength. In comparison, when the strength of soil increases with depth, the sliding zone will go right under the excavation wall. For the former, increase in excavation wall has virtually no effect on restricting the base heave because it is located within the sliding mass. For the latter, increase in strength of base soil can have a significant effect on reducing the base heave. Since the failure mechnism is similar to that of routinely used base stability analysis method, the calculated factor of safety against base heave is in good agreement with the amount of lateral wall deformation and base heave observed in the model test. In summary, the test model developed in this study has proved to be an useful means to study the base heave behavior in soft clay.

目 錄
中文摘要……………………………………………………….I
英文摘要………………………………………………………II
誌謝…………………………………………………………...III
目錄…………………………………………………………...IV
表目錄………………………………………………………..VII
圖目錄……………………………………………………....VIII
照片目錄……………………………………………………...XI
附錄………………………………………..………………..XIII
第一章 緒論…………………………………………………1
1.1研究動機與目的……………………………………….…….1
1.2研究內容……………………………………….…………….2
第二章 文獻回顧……………………………………………3
2.1落錐試驗(Fall cone test)之相關研究………………………..3
2.1.1落錐試驗之由來……………………………………….3
2.2.2落錐試驗應用於量測土壤強度……………………….4
2.2有關開挖穩定性分析方法之研究…………………………..5
2.2.1 內擠破壞型式分析方法之研究………………………6
2.2.2 底部隆起分析方法之研究……………………………10
2.2.2.1承載力破壞隆起分析……………………………10
2.2.2.2圓弧破壞隆起分析………………………………14
2.3離心機模型試驗儀器………………………………………..16
2.3.1離心機模型原理……………………………………….16
2.3.2離心機模型試驗於開挖行為之研究………………….17
第三章 試驗計畫、原理、儀器設備及試驗內容…………19
3.1試驗計劃……………………………………………………..19
3.2 模型試驗儀器設計原理…………………………………….19
3.2.1 FLAC程式原理簡介…………………………………20
3.2.2 模型與原型尺寸及性質比較…………………………20
3.2.3 模型與原型分析結果…………………………………21
3.3儀器設備介紹………………………………………………..22
3.3.1 落錐試驗儀……………………………………………22
3.3.2 開挖模型試驗儀………………………………………24
3.3.3 監測用數位相機………………………………………27
3.4試驗內容……………………………………………………..27
3.4.1基本物理試驗………………………………………….27
3.4.2落錐貫入試驗………………………………………….28
3.4.3開挖模型試驗………………………………………….29
第四章 試驗結果分析………………………………………31
4.1基本物理試驗結果…………………………………………..31
4.2落錐貫入試驗結果…………………………………………..31
4.3開挖模型試驗結果…………………………………………..33
4.3.1與案例結果比較……………………………………….33
4.3.2不同壁體貫入深度之比較…………………………….34
4.3.2.1底部隆起情況之探討……………………………34
4.3.2.2整體位移情況之探討……………………………36
4.3.3開挖面下方土壤強度增強後之結果比較…………….37
4.3.3.1改良區強度的決定………………………………38
4.3.3.2開挖面下方土壤強度增加後之結果比較分析…40
4.3.4模擬土層強度隨深度漸增之結果比較..……………...40
4.3.4.1開挖面下方土壤未改良之結果比較分析………41
4.3.4.2開挖面下方土壤改良情況下之結果比較分析…42
4.3.5將穩定係數降低後之結果比較……………………….43
4.3.5.1隆起量及擋土壁底部側位移之比較……………43
4.3.5.1由整體之位移情況作比較………………………44.
4.4 模型試驗結果綜合討論分析……………………………….44
第五章 結論與建議…………………………………………47
5.1結論…………………………………………………………..47
5.2建議…………………………………………………………..48
參考文獻…………..…………………………………………51

1、 Bjerrum, L., and Eide, O. (1956). “Stability of Strutted Excavations in Clay.” Geotechnique, Vol. 6, No. 1, London, England, pp. 32-47.
2、 British standards Institution (1990). Method of test for soils for civil engineering purposes.Britsh Standards Institution BS1377. London.
3、 Burland, J. B., Potts, D. M., and Walsh, N. M. (1981). "The Overall Stability of Free and Propped Embedded Cantilever Retaining Walls." Ground Engineering, Vol. 14, No. 5, pp. 28-38.
4、 Civil Engineering Code of Practice No.2(1951), Earth Retaining Structure.
5、 Davies, M. C. R. Almeida, M. S. S. and Parry, R. H. G., (1989). “Studies with Centrifuge Vane and Penetrometer Apparatus in a normal Gravity Field.” ASTM, Getoch. Testing J., Vol. 12, No. 3, pp. 195~203.
6、 Feng, T. W. (2000). “Fall-cone penetration and water content relationship of clays.” Geotechnique, Vol. 50, No. 2, pp. 181-187.
7、 Hansbo, S. (1957). ”A new approach to determination of the shear strength of clay by the fall-cone test.” Proc. Royal Sweden Geotech. Inst., No. 14, pp. 7-47.
8、 Houlsby, G. T. (1982). “Theoretical analysis of the fall-cone test.” Geotechnique, Vol. 32, No. 2, pp. 111-118.
9、 Karlsson, R. (1961). “Suggested improvement in the liquid limit test, with reference to flow properties of remoulded clays.” Proc. 5th Int. Conf. Soil Mech. Fdn Engng, Paris 1, pp. 171~184.
10、 Kimura et al. (1993).”Stability of unsupported and supported vertical cut in soft clay.” Proc. 11th Southeast Asian Geotech. Conf., pp. 61-70, Singapore.
11、 Kusakabe, O. (1982). Stability of excavation in soft clay. PhD. Thesis, Cambridge Univ.
12、 Liu, C. J., Hsieh, H. S., and Wang, K. R.(1994). “Undrained Strength Parameters selection of Taipei City Soft Clay for Deep Excavation Design.” Proceedings of the Second Young Asian Geotechnical Engineers Conference, AIT, Bangkok, Thailand.
13、 Lyndon, A. and Schofield, A. N. (1970). ”Centrifuge model test of short term failure in London clay.” Geotechnique, Vol. 20, No. 4, pp. 440-442.
14、 NAVFAC DM-7.2(1982), Department of the Navy Naval Facilities engineering Command, "Foundations and Earth Structures." Design Manual 7.2, Alexandria, Va.
15、 Peck, R. B. (1969). “Deep Excavation and Tunneling in Soft Ground.” Proceeding, seventh International Conference on Soil Mechanics and Foundation Engineering , State-of-the-Art Volume, Mexico City pp. 225-290.
16、 Skempton, A. W. (1951).“ The Bearing Capacity of Clays.” Bldg. Res. Cong., Div.l, London, pp. 180-189.
17、 Skempton, A. W. and Northey, R. D. (1953). ”The sensitivity of clays.“ Geotechnique, Vol. 3, No. 1, pp. 30-53.
18、 Swedish Standard Commission (1990). Geotechnical tests — cone liquid limit. Swedish Standards Commission, Stockholm, SS027120.
19、 Terzaghi, K. (1943). Theoretical Soil Mechanics. John Wiley and sons, Inc. New York, N. Y.
20、 Terzaghi, K. and Peck, R. B. (1967). Soil Mechanics in Engineering Practice. Second Edition, John Wiley and sons, Inc. New York, N. Y.
21、 Wood, D. M. and Wroth, C. P. (1978). “The use of the cone penetrometer to determine the plastic limit of soil.” Ground Engng. Vol. 11, No. 3, pp. 37.
22、 Zreik, D. A., Ladd, C. C., and Germaine, T. T. (1995). ” A new fall cone device for measuring the undrained strength of very weak cohesive soils.” Geotechnical Testing Journal, Vol. 18, No. 4, pp. 472-482.
23、 中華民國建築學會(民國77年)，建築技術規則建築構造編─基礎構造設計規範。
24、 王暉文(民國83年) ，「有限差分法用於台北地區深開挖工程分析之研究」，國立台灣科技大學營建工程研究所碩士論文。
25、 石正義譯(1992)「鑽探圖的判讀要領」，詹氏書局出版。
26、 李崇正、林志棟、林俊雄(1994)，「大地工程研究者之新工具:離心模型試驗」，岩盤工程研討會論文集，中壢，第649~669頁(1994)。
27、 胡敏一（民國87年），「軟弱粘土層開挖穩定性分析之探討」，國立台灣科技大學營建工程研究所碩士論文。
28、 陳煌銘(民國76年)，「深開挖引致之地盤移動」，地工技術雜誌，第20期，第19-33頁。
29、 廖洪鈞、許世宗（民國79年），「開挖擋土壁體之合理貫入深度探討」，地工技術雜誌，第32期，第78-89頁。
30、 劉泉枝、謝旭昇、黃志祥(1997)，「粘性土壤深開挖穩定性分析方法之探討」，第七屆大地工程學術研究討論會，台北金山，第629-638頁。