以三軸試驗探討非飽和紅土之力學行為

A Study on the Mechanics Behavior of Unsaturated Lateritic Soil by Triaxial Tests

李世傑(Shih-Chieh Li)

指導教授 ： 魏敏樺

國立臺北科技大學/工程學院/土木與防災研究所/碩士(2008年)

https://doi.org/10.6841/NTUT.2008.00301

摘要

本研究在探討非飽和殘積紅土之工程性質，以及吸力變化對非飽和土壤變形和抗剪強度特性的影響。本研究將針對林口紅土台地所取得之現地擾動土樣，製成重模試體，進行物理性質與三軸力學行為試驗，如單向度壓密、壓密不排水(CU)、壓密排水(CD)及常含水量(CW)等三軸壓縮試驗。
透過改良式三軸試驗儀，來探討在不同基質吸力下紅土之剪力強度變化情形，將不同三軸試驗結果之剪力強度做比較，再將試驗結果與前人研究進行討論與比較。本研究分兩大主軸做分析：一、得到壓密不排水(CU)試驗和常含水量(CW)的結果，與朱信安 (2004)和Yu (2006)的資料彙整，透過多元線性迴歸分析求出最佳化的破壞包絡面；二、著重於飽和土壤的臨界狀態分析，施作三軸壓密排水(CD)壓縮試驗，依試驗前後結果顯示，ν-lnp’的分佈圖在乾側面的變化較濕側面明顯。此外，紅土的臨界狀態線(CSL)在不同土壤構造下，其臨界狀態線的趨勢相似。將這些紅土相關參數應用於工程實務上，使工程設計開發更能精確地使用適當之土壤參數，並供做現地穩定性分析與破壞機制之數值模擬。

關鍵字

非飽和土壤 ； 臨界狀態 ； 破壞包絡面 ； 基質吸力 ； 紅土 ； 三軸壓密排水試驗 ； 三軸壓密不排水試驗 ； 三軸常含水量試驗

並列摘要

This study were discussing the properties of engineering on unsaturated residual lateritic soil, and the effects of unsaturated soil deformation and resisting shear strength due to changing suction. This study used intact and disturbed soils from Linkou terrace to make intact and remoulded specimens for triaxial tests, then proceeded some triaxial mechanical behavior tests, such as, triaxial consolidated undrained(CU) test, triaxial consolidated drained(CD) test and triaxial constant water content(CW) test.
With the improving apparatus of triaxial test, this study discussed the shear strength variation of lateritic soil under different matric suction, and compared with shear strength of different triaxial test results, then used these test results to discuss and compare with results of the former scholars.
This study divided into two major projects to make analysis: First, it obtained consolidated undrained(CU) test and constant water content(CW) test results, and then it combined with information of 朱信安(2004) and Yu (2006), finally, it used multiple linear regression analysis to find the best failure envelope; Second, it focused on critical state on saturated soil and did some triaxial consolidated drained(CD) test, according to the results of before and after testing, the variations of dry side are obviously than wet side on ν-lnp' plot. In addition, the critical state line(CSL) of the lateritic soil under the structures of different soils, the trend of its critical state line are similar. Applying the relevant parameters of the lateritic soil on the engineering design, can use the proper soil parameter accurately, and provide numerical simulation on the stability analysis and failure mechanism.

並列關鍵字

unsaturated soil ； critical state ； failure envelope ； matric suction ； lateritic soil ； triaxial consolidated drained test ； triaxial consolidated undrained test ； triaxial constant water content test

參考文獻

26. Donald, I. B. (1963), “Effective Stress Parameters in Unsaturated Soils”, in Proc. 4th Australia-New Zealand Conf. Soil Mech. Found. Eng. (Adelaide, South Australia), pp. 41-46.

1. Adams, B. A. and Wulfsohn, D. (1997), “Variation of the Critical-State Boundaries of an Agriculture Soil”, European Journal of Soil Science, Vol. 48, pp. 739-758.

3. Alonso, E. E., Gens, A., and Josa, A. (1990), “A Constitutive Model for Partly Saturated Soils”, Geotechnique, Vol. 40, No. 3, pp. 405-430.

6. ASTM D1557-91 (2002) “Standard Test Method for Laboratory Compaction Characteristics of Soil Using Modified Effort (56,000 ft-lb/ft3 (2,700 kN-m/m3))1.” West Conshohocken. Pa.

8. ASTM D2850-95 (2002) “Standard Methods for Unconsolidated, Undrained Triaxial Compression Test on Cohesive Soils.” West Conshohocken. Pa.