臨界土壤力學模型已被廣泛應用於飽和土壤，而非飽和土壤雖已有提出臨界狀態模型，但迄今因試驗數據資料有限及實驗程序複雜，因此對於非飽和臨界狀態之描述仍不斷修正中。本研究為探討非飽和粉質土壤其臨界狀態參數試驗之程序，將傳統三軸室進行修改，並加入吸力感測子與總體積量測系統，以量測試體受剪時基質吸力與總體積之變化，進而以超額基質吸力激發比作為剪動速率判定之依據。研究以定基質吸力(constant suction)與壓密排水(CD)方式施作非飽和三軸與三軸壓密試驗，其結果顯示本試驗之非飽和粉質土於軸向應變30%時到達臨界狀態，將臨界狀態點分別繪於p-q與p-v平面，可迴歸出臨界狀態線(CSL)以求得臨界狀態參數，並驗證本研究所採用之非飽和三軸試驗程序，而實驗亦發現非飽和土壤之正常壓密線(NCL)不與CSL相互平行，此與飽和土壤顯著不同。

Critical state soil mechanics has been well recognized for prediction the behaviors of saturated soils. Although unsaturated critical state soil models have been proposed, the development is slow due to limited testing data and highly complexity of the testing procedure. This experimental study aims to verify the testing procedure of unsaturated triaxial tests up to the critical state. A miniature suction probe used to monitor the suction in the middle plane and an inner cell system for total volume measurement are integrated in a triaxial testing system for unsaturated triaxial and isotropic consolidation tests. The maximum ratio of excess suction during shearing is used to determine the testing strain rate. Unsaturated triaxial tests of a silty soil with constant suction in drained condition were performed. The testing result reveals that the silty soil reaches critical state at 30% axial strain with constant excess suction, volume, and deviator stress. The critical state parameters are determined from the critical state line (CSL) on p-q and p-v planes and the consistence of the results confirms the validation of the testing procedure in this study. This experimental study also finds that the normal consolidation line is not parallel with the CSL for unsaturated soils, while in saturated soils they are parallel with each other.

1.王雅琪(2012)，「非飽和土壤中應力狀態參數對剪力波速影響之討論」，國立成功大學土木工程研究所碩士論文。
2.林琬芳(2008)，「LabVIEW應用於自動化土壤三軸K0試驗系統之開發」，國立臺北科技大學土木與防災研究所碩士論文。
3.Alonso, E. E., Gens, A. and Josa, A. (1990). “A constitutive model for partially saturated soils.” Géotechnique, 40(3), pp.405-430.
4.Bishop, W. (1959). “The principle of effective stress.” Lecture delivered in Oslo, Norway, 1955; published in Technisk Ukeblad, 106(39), pp. 859-863.
5.Bishop, W. and Blight G. E. (1963). “Some aspects of effective stress in saturated and unsaturated soils.” Géotechnique, 13(3), pp.177-197.
6.Bishop, W. and Donald, I. B. (1961). “The experimental study of partly saturated soil in the triaxial apparatus.” Proceedings of the 5th International Conference on Soil Mechanics and Foundation Engineering, Paris France, 1, pp. 13-21.
7.Bishop, W. and Gibson, R. E. (1963). “The influence of the provisions for boundary drainage on strength and consolidation characteristics of soils measured in the triaxial apparatus.” Laboratory Shear Testing of Soils, ASTM, STP No. 361, pp.435-458.
8.Casagrande, A. (1963). “The determination of the preconsolidation load and its practical significance.” Discussion D-34, Proceedings of the 1th International Conference on Soil Mechanics and Foundation Engineering, Cambridge, 3, pp.60-64.
9.Cui, Y. J. and Delage, P. (1996) “Yielding and plastic behaviour of an unsaturated compacted silt.” Géotechnique, 46(2), pp.291-311.
10.Estabragh, A. R. and Javadi, A. A. (2008). “Critical state for overconsolidated unsaturated silty soil.” Canadian Geotechnical Journal, 45(3), pp.408-420.
11.Fredlund, D. G. (1970). “Second Canadian geotechnical colloquium: appropriate concepts and technology for unsaturated soils.” Canadian Geotechnical Journal, 16(1), pp.121-139.
12.Fredlund, D. G. (1979). “Second Canadian Geotechnical colloquium: appropriate concepts and technology for unsaturated soils.” Canadian Geotechnical Journal, 16(1), pp.121-139.
13.Fredlund, D. G. and Morgenstern, N. R. (1977). “Stress state variables for unsaturated soils.” Journal of Geotechnical Engineering Division, ASCE, GT5, 103, pp.447-466.
14.Fredlund, D. G. and Rahardjo, H (1987). “Soil mechanics principles for highway engineering in arid regions.” Transportation Research Record 1137, pp.1-11.
15.Fredlund, D. G. and Rahardjo, H. (1993). Soil mechanics for unsaturated soils. New York, Wiley.
16.Fredlund, D. G., Morgenstern, N. R. and Widger, R. A. (1978). “The shear strength of unsaturated soils.” Canadian Geotechnical Journal, 15(3), pp.313-321.
17.Fredlund, D. G., Xing, A., Fredlund, M. D. and Barbour, S. L. (1995). “The relationship of the unsaturated soil shear strength to the soil-water characteristic curve.” Canadian Geotechnical Journal, 32(3), pp.440-448.
18.Gan, K. M., Fredlund, D. G. and Rahardjo, H. (1988). “Determination of shear strength parameters of an unsaturated soil using the direct shear test.” Canadian Geotechnical Journal, 25(3), pp.500-510.
19.Hilf, J. W. (1956). “An investigation of pore-water pressure in compacted cohesive soils.” PhD thesis, Technical Memo No. 654, United States Bureau of Reclamation, Denver, CO.
20.Ho, D. Y. F. and Fredlund, D. G. (1982). “Increase in shear strength due to soil suction for two Hong Kong soils.” Proceedings of ASCE Geotech. Conf. Eng. and Construction in tropical and residual soils, Honolulu, January, pp.263-295.
21.Krahn, J. and Fredlund, D. G. (1972). “On total matric and osmatic suction.” Journal of Soil Science, 114(5), pp.339-348.
22.Maatouk, A., Leroueil, S. and La Rochelle, P. (1995). “Yielding and critical state of a collapsible unsaturated silty soil.” Geotechnique 45(3), pp.465-477.
23.Muraleetharan, K. K. and Granger, K. K. (1999). “The use of miniature pore pressure transducers in measuring matric suction in unsaturated soils.” Geotechnical Testing Journal, GTJODJ, 22(3), pp.226-234.
24.Murray, E. J. and Sivakumar, V. (2001). Unsaturated Soils: A fundamental interpretation of soil behaviour, Wiley-Blackwell.
25.Ng, C. W. W. and Menzies, B. (2007). Advanced Unsaturated Soil Mechanics and Engineering. London, Taylor and Francis.
26.Ng, C. W. W., Zhan, L. T., and Cui, Y. J., (2002). “A new simple system for measuring volume changes in unsaturated soils,” Canadian Geotechnical Journal, Vol.39, pp. 757–764.
27.Ng. C. W. W., Cui, Y., Chen, R. and Delage, P. (2007). “The axis-translation and osmotic techniques in shear testing of unsaturated soils: a comparison.” Soils and Foundations, 47(4), pp.678-684.
28.Oloo, S. Y. and Fredlund, D. G. (1996). “A method for determination of  b for statically compacted soils.” Canadian Geotechnical Journal, 33, pp.272-280.
29.Ridley, A. M. and Burland, J. B. (1995). “Measurement of suction in materials which swell.” Applied Mechanics Reviews, 48(9), pp.727-732.
30.Satija, B. S. (1978). “Shear behavior of partly saturated soils.” PhD thesis, Indian Inst. of Technol., Delhi.
31.Satija, B. S. and Gulhati, S. K. (1979). “Strain rate for shearing testing of unsaturated soil.” Proceedings of the 6th Asian Reg. Conf. Soil Mech. Found. Eng., Singapore, pp.83-86.
32.Sivakumar, V. (1993). “A critical state framework for unsaturated soils.” PhD thesis, University of Sheffield, UK.
33.Sivakumar, V., Sivakumar, R., Boyd, J., Mackinnon, P. and (2010). “Mechanical behaviour of unsaturated kaolin (with isotropic and anisotropic stress history). Part 2: performance under shear loading.” Géotechnique, 60(8), pp.595-609.
34.Terzaghi, K. (1936). “The shear resistance of saturated soils.” Proceedings of the 1th International Conference on Soil Mechanics and Foundation Engineering, Cambridge, 1, pp.54-56.
35.Toll, D. G. and Ong, B. H. (2003). “Critical-state parameters for an unsaturated residual sandy clay.” Géotechnique, 53(1), pp.93-103.
36.Watson, K. K. (1967). “A recording field tensiometer with rapid response characteristics.” Journal of Hydrology, 5, pp.33-39.
37.Wang, Q., D., Pufahl E. and Fredlund, D. G. (2002). “A study of critical state on an unsaturated silty soil.” Canadian Geotechnical Journal 39(1), pp.213-218.
38.Wheeler , S. J. and Sivakumar, V. (1993). “Development and application of a critical state model for unsaturated soil.” Predictive soil mechanics. Proceedings of the wroth memorial symposium. ST Catherine's college, OXFORD, Thomas Telford Limited, pp.709-728.
39.Wheeler, S. J. and Sivakumar, V. (1995). “An elasto-plastic critical state framework for unsaturated soil.” Géotechnique 45(1), pp.35-53.