根據含水量推估黏土之不排水剪力強度與歷史應力

Estimating in-situ undrained shear strength and stress history of clays via water content

徐碩鴻(Shou-Hong Hsue)

指導教授 ： 卿建業

國立臺灣大學/工學院/土木工程學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.01437

摘要

現地調查對於土木工程施工上，可以說是非常重要的一環；因為根據不同試驗所量測到的工程參數，為工程師在參與設計時的重要依據；但是在現地調查的同時，試驗誤差、試體的擾動誤差、人為誤差都會造成許多的不確定性，像是在求得現地不排水剪力強度中，使用UC (unconfined compression)無圍壓縮試驗、FV (field vane)十字片剪力強度試以及CPT (cone penetration test)圓錐貫入試驗皆可以求得現地不排水剪力強度，但是在試驗過程中的剪動方式、限制排水與否…等等；皆會是影響試驗結果進而影響參與設計的設計參數；有鑑於此，本研究以現地中最容易取得之含水量為出發點，蒐集同時擁有有效覆土應力、預壓密力、現地不排水剪力強度、重模黏土不排水剪力強度資訊進行分析；其中同時擁有五筆資訊作為分析資料庫以提供分析資料使用；另外無法同時擁有五筆資訊作為驗證資料庫以驗證分析資料是否符合實際；除此之外，根據前人文獻中的經驗公式加以驗證分析資料的正確性，進而提供工程師在參與設計時所需之參數。

關鍵字

液性指數 ； 不排水剪力強度 ； 預壓密力 ； 關連性 ； 可靠度分析

並列摘要

Liquidity index has been long believed to correlate to design parameters of clays such as undrained shear strength, sensitivity, overconsolidation ratio, etc. Such correlations are important because liquidity index is usually the most basic and available index from site investigation information. This study compiles a large database of lightly overconsolidated and sensitive clays to construct the joint probability distribution among the liquidity index and several design parameters. This joint distribution is then used to simulate the correlations between liquidity index and the design parameter of interest. The main results are a set of equations whose inputs are the observed liquidity index and outputs are the updated mean values and coefficients of variation (c.o.v.) of the design parameters of interest, which are necessary for reliability-based design. These equations are further validated by another independent database of lightly overconsolidated and sensitive clays as well as by empirical equations proposed in literature.

並列關鍵字

liquidity index ； undrained shear strength ； preconsolidation stress ； correlation

參考文獻

Alberro, J.A. and Santoyo, E.Y. (1973). Long - term behaviour of Mexico City Clay. Proceedings of the 8th International Conference on Soil Mechanics and Foundation Engineering, 1, 1-9.

Baracos, A., Graham, J. and Domaschuk, L. (1980). Yielding and rupture in a lacustrine clay. Canadian Geotechnical Journal, 17(4), 559-573.

Berre, T. and Bjerrum, L. (1973). Shear strength of normally consolidated clays. Proceedings of the 8th International Conference on Soil Mechanics and Foundation Engineering, Moscow, 1(1), 39-49.

Bishop, A.W., Webb, D.L. and Lewin, P.I. (1965). Undisturbed samples of London clay from the Ashford common shaft: Strength - effective stress relationships. Geotechnique, 15(1), 1-31.

Bjerrum, L. and Simons, N.E. (1960). Comparison of shear strength characteristics of normally consolidated clays. ASCE Research Conference on Shear Strength of Cohesive Soils, 711-726.