بررسی اثرات دست خوردگی نمونه بر روی خصوصیات مقاومتی خاک رسی

درفشی نو, محمد; علیزاده مجدی, علیرضا; دبیری, روزبه

doi:10.22084/nfag.2023.27858.1556

بررسی اثرات دست خوردگی نمونه بر روی خصوصیات مقاومتی خاک رسی

نویسندگان

¹ کارشناسی‌ارشد مهندسی ژئوتکنیک، گروه مهندسی عمران، واحد تبریز، دانشگاه آزاد اسلامی، تبریز، ایران

² استادیار گروه مهندسی عمران، واحد تبریز، دانشگاه آزاد اسلامی، تبریز، ایران

³ دانشیار گروه مهندسی عمران، واحد تبریز، دانشگاه آزاد اسلامی، تبریز، ایران

10.22084/nfag.2023.27858.1556

چکیده

یکی از موضوعات چالش برانگیز در زمین شناسی مهندسی و ژئوتکنیک، تاثیر دست خوردگی نمونه‌های خاک در تعیین خصوصیات مختلف فیزیکی و مقاومتی می‌باشد. دست‌خوردگی در کلیه مراحل شامل حفاری گمانه، تهیه، ارسال و آماده‌سازی ‌نمونه و انجام آزمایش در آزمایشگاه روی می‌دهد. در عمل تهیه نمونه دست نخورده ایدهآل ممکن نمی‌باشد. بدلیل مشکلات تهیه نمونه‌های دست‌نخورده به ویژه در لایه‌های خاکی، در بیشتر مواقع آزمایش بر روی نمونه بازسازی ‌شده انجام می‌گیرد. مطالعات متعددی در مورد روشهای ارزیابی دست‌خوردگی نمونه انجام گرفته است. هدف این تحقیق ارزیابی اثرات دست‌خوردگی بر روی خصوصیات مقاومتی خاکهای رسی براساس مطالعه موردی شهر تبریز میباشد. با انجام آزمایشات فشاری محصور نشده و برش مستقیم بر روی نمونههای دست‌نخورده و بازسازی‌ شده، اثرات دستخوردگی و حساسیت نمونه‌ها بررسی شده است. به طورکلی مقاومت فشاری نمونه‌های بازسازی‌ شده در اثر دست‌خوردگی حدود 20 الی 45 درصد کاهش می‌یابد. ضمن تعیین ضریب همبستگی اسپیرمن، تحلیل رگرسیون خطی و غیرخطی به منظور برآورد مقاومت فشاری نمونه دست‌نخورده انجام گردید. نسبت حساسیت بین 1 الی 2 بدست آمده و در رده با حساسیت کم قرار می‌گیرند. همبستگی بین نتایج مقاومت نمونه‌های دست‌نخورده و بازسازی ‌شده درآزمایش برش مستقیم با انجام تحلیل رگرسیون مطالعه گردید. بر اساس این نتایج، چسبندگی نمونههای دست خورده به طور متوسط 4/12 درصد کاهش یافته ولی برای تغییرات زاویه اصطکاک داخلی رابطه معنی‌داری بدست نمیآید.

کلیدواژه‌ها

عنوان مقاله [English]

Evaluation of the Specimen Disturbance Effects on the Strength Properties of Clayey Soils

نویسندگان [English]

M. Derafshinou ¹
A. Alizadeh Majdi ²
R. Dabiri ³

¹ M. Sc. of Geotechnical Engineering, Dept., of Civil Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran

² Assist. Prof., Dept., of Civil Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran

³ Assoc. Prof., Dept., of Civil Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran

چکیده [English]

One of the challenging subjects in geological and geotechnical engineering is the effects of soil specimen disturbance in order to determine several physical and strenght characteristics. Disturbance occurs in all stages, including drilling the borehole, preparing, transporting and conducting tests in the laboratory. Practically, it is impossible to prepare an ideal undisturbed sample. Due to the difficulties of preparing undisturbed samples, especially in soil layers, the tests are mostly performed on the remolded samples. Several studies have been conducted on the methods of evaluating sample disturbance. The target of this study was to evaluate the effects of disturbance on the strenght properties of clay soils as case study of Tabriz city. By conducting uniaxial compressive and direct shear tests on undisturbed and remolded samples, the effects of disturbance and sensitivity of the samples were investigated. Generally, the compressive strength of remolded samples decreases due to disturbance. In addition to determining Spearman's correlation coefficient, linear and non-linear regression analysis were performed in order to estimate the compressive strength of the undisturbed sample. By determining the sensitivity ratio, the sensitivity of samples is low. Correlation between the strength of undisturbed and remolded samples in direct shear test, including cohesion and internal friction angle, was studied by performing regression analysis.

کلیدواژه‌ها [English]

Clayey soil
Remolded specimen
Cohesion
Internal friction

مراجع

Afrazi, M., and Yazdani, M (2019) Investigating the effect of disturbance on the results of direct shear test. National Conference on Civil Engineering and Architecture in 21st Century Urban Managemen, ISC96170-82101. (In Persian)

Afrazi, M., Yazdani, M., Talesh, M., and Fakhimi, A (2019) Numerical analysis of effective parameters in direct shear test by hybrid discrete – finite element method, Scientific Research Journal of Modares Civil Engineering, 18 (3): 13—24, (In Persian).

Alizade Majdi, A. R., and Dabiri, R (2019) Estimation of SPT test results using by probabilistic methods and artificial neural network in clay layers. ) case study: Clay layers of Tabriz, Advanced Applied Geology, doi.org/10.22055/ aag. 26391.1871. (In Persian).

Alizadeh Majdi, A. R., Dabiri, R., Ganjian, N., and Ghalandarzadeh, A (2020) Evaluation of the Specimen Disturbance Effects in the Consolidation Test Using Shear Wave Velocity, Geotechnical and Geological Engineering, 38: 2927–2943.

ASTM-D 2166 (2013) Standard test method for unconfined compressive strength of cohesive soils, Annual book of ASTM standards.

ASTM D6528 (2007) Standard Test Method For Consolidated Undrained Direct Simple Shear Testing Of Cohesive Soils, Annual book of ASTM standards.

ASTM D 854 (2002) Standard test method for specific gravity of soil solids by water pycnometer, Annual book of ASTM standards.

ASTM D422 (1963) Standard Test Method for article-Size Analysis of Soils, Annual book of ASTM standards (reapproved 1998).

ASTM D2216 (2019) Standard Test Method for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass, Annual book of ASTM standards.

ASTM D 4318 (1995) Standard test method for liquid limit, plastic limit an plasticity index for soils, Annual book of ASTM standards.

ASTM D2487 (1998) Classification of soils for engineering purposes unified soil classification system, Annual book of ASTM standards.

Golpasand, M. B., Nikoudel, M., Asghari, E., and Yasrebi, S. S (2007) Comparison of CPTu Test and Laboratory Test Results in Determination of Shear Strength of Uromieh Lake Bridge Site, Sceintific Quaterly Journal Geosciences, 15: 12-21 (In Persian).

Holtz, R. D., and Kovacs, W. D (1981) An introduction to geotechnical engineering. Prentice-Hall, Englewood Cliffs.

Hooshmand, A., Aminfar, M. H., Asghari, E., and Ahmadi, H (2011) Mechanical and Physical Characterization of Tabriz Marls, Iran, Geotechnical and Geological Engineering, 30: 219-232. doi.org/10.1007/s10706-011-9464-3.

Karina, R. Dahl, K. R., Boulanger, R. W., DeJong, J. T., and Driller, M. W (2010) Effects of Sample Disturbance and Consolidation Procedures on Cyclic Strengths of Intermediate Soils. Fifth International Conference on recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics, San Diego California. (https://scholarsmine.mst.edu/icrageesd).

Kontopoulos, N. S (2012) The effects of sample disturbance on preconsolidation pressure for normallconsolidated and overconsolidated clays. Massachusetts Institute of Technology, in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in the Field of Civil and Environmental Engineering. (http://hdl.handle.net/1721.1/74419).

Liang, Y., Cao L., and Lio, J (2015) Statistical Correlations between SPT N-Values and Soil Parameters. Technical Report, Department of Civil Engineering, Ryerson University, (www.researchgate.net/publication/ 281109498).

Lunne, T., Berre T., Andersen, K. H., Sjursen, M., and Mortensen, N (2011) Effects of sample disturbance on consolidation behaviour of soft marine Norwegian clays. Canadian Geotechnical Journal, (https://doi: 10.1139/t06-040).

Ouhadi, V. R., Ghalandarzadeh, A., and Behnia, K (1993) Engineering characteristics and properties of marly soils. Proceedings of the second international seminar on soil mechanics and foundation engineering of Iran, Tehran, Iran. (In Persian).

Parsa, Z., Asghari Kalajahi, E., and Hajialilou Bonab, M (2022) Investigating the problems of marly and sandy soils in Nagin Park area of Tabriz in the implementation of deep excavation projects, New Findings in Applied Geology, 15: 47-65, doi: 10.22084/nfag.2021.22961.1438.

Ruge, C., Gómez, M., and Rojas, P (2019) Thixotropic behaviour study of clayey soils from the lacustrine deposits of Bogotá high plateau. 5th International Meeting for Researchers in Materials and Plasma Technology, doi: 10.1088/1742-6596/1386/1/012050.

Skemption, A. W., and Northey, R. D (1952) The sensitivity of clays. Géotechnique, doi:/10.1680/geot.3.1.30.

Shosh Pasha, E., Farhadi, A., and Barjeste, B (2005) Evaluating of the sensitivity and thixotropy of silty clay soil, First National Congress of Civil Engineering, Sharif University of Technology. (In Persian).

Terzaghi, K., Peck, R. B., and Mesri, G (1996) Soil Mechanics in Engineering Practice, John Wiley & Sons, Inc., New York

Touiti, L., Lmpe, W. V., and Bouassida, M (2009) Discussion on Tunis soft soli sensitivity, Geotechnical and geological engineering, 27: 631-643, doi:10.1007s10706-009-9263-2.

Zhang, X., Kong, L., Md. And Sayem, H (2017) Thixotropic mechanism of clay a microstructural investigation, Soils and Foundations, 57: 23-35, doi: 10.1016/j.sandf.2017.01.002.