夯實土壤長時間處於不飽和狀態，可能受日曬及降雨等天氣因素而改變土壤內部含水量，進而影響強度及勁度等。本研究針對不飽和夯實紅土進行一系列室內試驗，包括土壤基本物性試驗、無圍壓縮試驗、超音波試驗及不飽和三軸暨彎曲元件試驗。然後根據這些試驗結果，探討基質吸力對土壤波速、視凝聚力及應變相依模數之影響，並建立簡易方法來評估不飽和土壤性質。
試驗結果顯示，隨著基質吸力提升，土壤波速、視凝聚力及應變相依模數皆隨之提升。深入探討土壤波速與視凝聚力關係，發現兩者呈線性相關。以此為根據，建立波速推估視凝聚力評估式，推估結果良好，MAPE值約為20%。因此，工程上以簡易的非破壞性試驗來評估不飽和土壤之剪力強度應屬可行。夯實土壤應變相依模數探討結果顯示，在相同吸力下模數大小為濕側大於OMC，乾側最小。原因為乾側飽和過程中吸收水體積最多，導致顆粒間隙較大。而三側之不飽和土壤模數衰減皆較飽和土壤快。以γ0.7作為模數衰減指標值，發現強度越高其γ0.7值隨之遞減，也就是模數衰減越快。故基質吸力提高，無圍壓縮強度也隨之提高，進而使模數衰減越快。

Compacted soil is often in an unsaturated state. Weather factors such as sunlight and rainfall will change the water content of the soil, thereby affecting its strength and stiffness. This research conducted a series of tests on unsaturated compacted lateritic soils, including the soil basic property test, the unconfined compression test, the ultrasonic test and the unsaturated triaxial test with bender element. Test results were used to study the influence of the matric suction on the soil wave velocity, the apparent cohesion and the strain-dependent modulus. Simplified methods were developed to evaluate the properties of unsaturated soil.
The test results show that when the matric suction increases, the soil wave velocity, the apparent cohesion, and the strain-dependent modulus all increase. And the apparent cohesion is linearly related to the soil wave velocity. Based on this, the wave velocity is used to estimate the apparent cohesion. The estimation result is good, the value of MAPE is about 20%. Therefore, it should be feasible to use simple non-destructive tests to evaluate the shear strength of unsaturated soils. The results of the strain-dependent modulus of compacted soils show that the modulus is larger than the OMC on the wet side and the smallest on the dry side under the same suction. The reason is that the volume of absorbed water is the largest during the saturation process of the dry side, resulting in a larger particle spacing. The modulus of unsaturated soils of the three compaction conditions degrade faster than that of the saturated soil. Taking γ_0.7 as the modulus degradation index value, it is found that the value of γ_0.7 decreases with strength increases. As the results, matric suction increases, the unconfined compression strength increases, and the modulus degrades faster.

1. 丁楷恩，「不飽和夯實紅土之土壤波速與剪力強度及土壤模數之關係」，碩士論文，國立台灣科技大學營建工程系，(2018)。
2. 王正君，「乾、濕化路徑與夯實狀態對土壤基質吸力之影響」，碩士論文，國立台灣科技大學營建工程系，(2008)。
3. 王旭暉，「以基質吸力觀點探討不飽和夯實紅土無圍壓縮強度與視凝聚力關係」，碩士論文，國立台灣科技大學營建工程系，(2016)。
4. 江宇祥，「不飽和夯實紅土之視凝聚力與剪力強度特性」，碩士論文，國立台灣科技大學營建工程系，(2014)。
5. 李豪智，「乾濕化路徑下基質吸力對不飽和夯實紅土應變相依土壤模數之影響」，碩士論文，國立台灣科技大學營建工程研究所，(2016)。
6. 李家豪，「Apparent Cohesion and Small-Strain Soil Modulus of Unsaturated Compacted Lateritic Soil」，碩士論文，國立台灣科技大學營建工程系，(2017)。
7. 林郁博，「不飽和夯實紅土波速與力學性質關係之研究」，碩士論文，國立台灣科技大學營建工程系，(2017)。
8. 周勃翰，「不飽和夯實紅土視凝聚力與吸力特性之試驗探討」，碩士論文，國立台灣科技大學營建工程系，(2015)。
9. 拱祥生，「降雨對不飽和土壤邊坡穩定性之影響研究」，碩士論文，國立台灣科技大學營建工程研究所，(1999)。
10. 拱祥生，「不飽和紅土基質吸力行為及其在工程之應用」，博士論文，國立台灣科技大學營建工程研究所，(2011)。
11. 張哲維，「Study of Apparent Cohesion from Unconfined Compression Test under Unsaturated Soil Concepts」，碩士論文，國立台灣科技大學營建工程系，(2013)。
12. 張宇翔，「以基質吸力與土壤波速探討不飽和夯實紅土之剪力強度及模數特性」，碩士論文，國立台灣科技大學營建工程系，(2019)。
13. 廖志穎，「不飽和路基土壤濕化及剪力模數研究」，碩士論文，國立台灣科技大學營建工程系，(2007)。
14. 龔東慶，「考慮台北沉泥質黏土小應變行為之深開挖地表沉陷分析」，博士論文，國立台灣科技大學營建工程系，(2003)。
15. Atkinson, J. H., Sallfors, G., “Experimental Determination of Soil Properties”, Proceedings of the 10th ECSMFE, Vol. 3, Florence, pp. 915-956, (1991).
16. Chan, C. M., “Bender Element Test in Soil Specimens: Identifying the Shear Wave Arrival Time”, Electronic Journal of Geotechnical Engineering, 15,pp. 1263-1276,(2010).
17. Croney, D. and J.D. Coleman., “Pore Pressure and Suction in Soils”, In Proceedings of the Conference on Pore Pressure and Suction in Soils, Butterworths, London, pp.31-37, (1961).
18. Costa Filho, L. D. M., ”Measurement of axial strains in triaxial tests on London Clay”, Geotechnical Testing Journal, Vol.8, No.1, pp.3-13, (1985).
19. Cuccovillo, T., “The measurement of local axial strains in triaxial tests using LVDTs.”, Géotechnique, Vol.47, No.1, pp.167-172, (1997).
20. Dyvik, R., & Madshus, C., “Lab Measurements of Gmax Using Bender Elements.”, In Advances in the art of testing soils under cyclic conditions, pp.186-196. ASCE, (1985).
21. Fredlund, D. G., and Morgenstern, N. R., “Stress State Variables for Unsaturated Soil.” Journal of Geotechnical Engineering, ASCE, GT5, Vol.103, pp.447-466, (1977).
22. Fredlund, D. G., Morgenstern, N. R., & Widger, R. A., “The shear strength of unsaturated soils.”, Canadian geotechnical journal, Vol.15, No.3, pp.313-321, (1978).
23. Fredlund, D. G., Rahardjo, H., & Gan, J. K. M., “Non-linearity of strength envelope for unsaturated soils.”, Proc. 6th Int. Conf. Expansive Soils, New Delhi, Vol.1, pp. 49-54, (1986).
24. Fredlund, D. G. and Rahardjo, H., “Soil Mechanics for Unsaturated Soils.”, John Wiley, New York, (1993).
25. Fredlund, D. G., & Xing, A., “Equations for the soil-water characteristic curve.”, Canadian geotechnical journal, Vol.31, No.4, pp.521-532, (1994).
26. Gasparre, A., Hight, D. W., Coop, M. R., & Jardine, R. J., “The laboratory measurement and interpretation of the small-strain stiffness of stiff clays.”, Geotechnique 64, No.12, 942–953, (2014).
27. Holtz, R. D., & Kovacs, W. D., “An introduction to geotechnical engineering.”, (1981). 2th edition,Pearson Education.
28. Ho, D. Y. F. and Fredlund, D. G., “A Multistage Triaxial Test for Unsaturated Soils”, Geotechnical Testing Journal, Vol.5, No.1, pp. 18-28, (1982).
29. Isah, B. W., Mohamad, H., Harahap, I. S. H., “Measurement of small-strain stiffness of soil in a triaxial setup: Review of local instrumentation”, International Journal of Advanced and Applied Sciences, pp.15-26, (2018).
30. Kai, Y, Qingsheng, C, Jiahui, H, Huawen, X, Fook, H. L., “Strain-Dependent Shear Stiffness of Cement-Treated Marine Clay. ” Journal of Materials in Civil Engineering, ASCE, Vol. 30, Issue 10(2018).
31. Leong, E. C., Yeo, S. H., & Rahardjo, H., “Measurement of wave velocities and attenuation using an ultrasonic test system”, Canadian Geotechnical Journal, Vol.41, No.5, pp.844-860, (2004).
32. Lin, H. D., Kung, J. H. S., and Wang, C. C., “Matric Suction and Shear Modulus of Unsaturated Compacted Lateritic Soil Subjected to Drying and Werting”, Abstracts of The Sixth Japan-Taiwan Joint Workshop on Geotechnical Hazards from Large Earthquakes and Heavy Rainfalls, pp.139-140, July 12-15, 2014, Kitakyushu, Japan, (2014).
33. Lin, H. D., Wang, C. C., and Kung, J. H. S., “Wetting and Drying on Matric Suction of Compacted Cohesive Soil”, Proceedings, ISOPE-2015, the 25th International Ocean and Polar Engineering Conference (with CD-ROM), Vol.2, pp.1069-1075, Kona, Big Island, Hawaii, USA, (2015).
34. Lin, H. D., Jiang, Y. S., Wang, C. C., & Chen, H. Y., “Assessment of Apparent Cohesion of Unsaturated Lateritic Soil Using an Unconfined Compression Test.”, Proceedings of Advances in Civil, Environmental, and Materials Research (ACEM’16), (2016).
35. Lin, H. D. , Wang, C. C., & Wang, Xu-Hui “A simplified method to estimate the total cohesion of unsaturated soil using an UC test”, Geomechanice and Engineering Volume 16 Issue6, Pages.599-608, (2018).
36. Laureano, R. H. ,Eduardo, A. S. , Anand, J. P. , “Stiffness of intermediate unsaturated soil from simultaneous suction-controlled resonant column and bender element testing”, Engineering Geology Volume 188, Page 10-28, (2015).
37. Mladen, V. ,Ricardo, D. , “EFFECT OF SOIL PLASTICITY ON CYCLIC RESPONSE”, Journal of Geotechnical Engineering, Vol. 117,Issue 1(1991).
38. Miller, C. J., Yesiller, N., Yaldo, K., and Merayyan, S., “Impact of Soil Type and Compaction Conditions on Soil Water Characteristic”, Journal of Geotechnical and Geoenvironmental Engineering, Vol.128, No.9, pp. 733-742, (2002).
39. Mendoza, C. E., Colmenares, J. E., & Merchan, V. E., “Stiffness of an unsaturated compacted clayey soil at very small strains.”, Proc, Int. Symp. on Advanced Experimental Unsaturated Soil Mechanics, pp. 199-204, (2005).
40. Nakagawa, K., Soga, K., & Mitchell, J. K., “Pulse transmission system for measuring wave propagation in soils.”, Journal of Geotechnical Engineering, Vol.122, No.4, pp.302-308, (1996).
41. Nyunt, T.T., Leong, E.C. and Rahardjo, H., “Stress-strain behavior and shear strength of unsaturated residual soil from triaxial tests”, Conference on Unsaturated Soils: Theory and Practice, Thailand, (2011).
42. Oh, W. T., & Vanapalli, S. K., “The relationship between the elastic and shear modulus of unsaturated soils.”, Unsaturated soils, proceedings of the 5th international conference on unsaturated soils (eds E. Alonso and A. Gens), pp.341-346, (2011).
43. Stephenson, R. W., “Ultrasonic testing for determining dynamic soil moduli.”, Dynamic Geotechnical Testing, ASTM International, (1978).
44. Senthilmurugan, T., & Ilamparuthi, K., “Study on Compaction Characteristics and Strength through Ultrasonic Method.”, Advances in Pavement Engineering, pp.1-12, (2005).
45. Sawangsuriya, A., “Wave Propagation Methods for Determining Stiffness of Geomaterials.”, Wave Processes in Classical and New Solids, InTech, (2012).
46. Thu, T. M., Rahardjo, H., & Leong, E. C., “Shear strength and pore-water pressure characteristics during constant water content triaxial tests.”, Journal of Geotechnical and Geoenvironmental Engineering, Vol.132, No.3, pp.411-419, (2006).
47. Viggiani, G., & Atkinson, J. H., “Stiffness of fine-grained soil at very small strains.”, Géotechnique, Vol.45, No.2, pp.249-265, (1995).
48. Vanapalli, S. K., Fredlund, D. G., & Pufahl, D. E., “The relationship between the soil-water characteristic curve and the unsaturated shear strength of a compacted glacial till.”, Geotechnical Testing Journal, Vol.19, No.3, pp.259-268, (1996).
49. Xiao, H., Lee, F. H., Yao, K., Ho, J., & Liu, Y. “Miniature LVDT setup for local strain measurement on cement-treated clay specimens”, Journal Marine Georesources & Geotechnology (2018).
50. Yesiller, N., Inci, G., & Miller, C. J., “Ultrasonic testing for compacted clayey soils.”, Advances in Unsaturated Geotechnics, pp.54-68, (2000).
51. Yang, S. R., Lin, H. D. Kung, J. H. S. and Liao, J. Y., “Shear Wave Velocity and Suction of Unsaturated Soil Using Bender Element and Filter Paper Method”, Journal of GeoEngineering, Vol.3, No.2, pp. 67-74, (2008).