تأثیر رطوبت و کربنات کلسیم بر مقاومت برشی آبرفت نوع D جنوب تهران

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه زمین‌شناسی کاربردی، دانشکده علوم زمین، دانشگاه خوارزمی، تهران، ایران

2 گروه مهندسی عمران، دانشکده مهندسی، دانشگاه بوعلی‌سینا، همدان، ایران.

چکیده

در این پژوهش، تأثیر همزمان رطوبت و درصد کربنات کلسیم بر مقاومت برشی آبرفت نوع D در جنوب تهران مورد بررسی قرار گرفت. 50 نمونه خاک از مناطق جنوبی شهر تهران (شامل مناطق 11 تا 20) جمع‌آوری و آزمایش‌ها برای سه سطح رطوبت (8، 14 و 31%) انجام شد. نتایج نشان می‌دهد که افزایش رطوبت تا حد اشباع (31%)، مقاومت برشی خاک را به‌طور چشمگیری کاهش می‌دهد؛ به‌طوری‌که چسبندگی (c) از 5.20 kPa در رطوبت 8% (نزدیک‌ترین سطح رطوبت به حالت خشک) به 18/3 kPa در رطوبت 31% کاهش یافت (کاهش 38.8%)، و زاویه اصطکاک داخلی (φ) از 25.5 درجه به 17.1 درجه کاهش پیدا کرد. تحلیل رگرسیون آمیخته چندمتغیره تأیید می‌کند که رطوبت (β = -1.78, p < 0.001) قوی‌ترین پیش‌بینی‌کننده چسبندگی است. همچنین، شاخص خمیری (PI) دومین پیش‌بینی‌کننده معنادار چسبندگی (β = 0.41, p = 0.002) شناسایی شد. در مقابل، مقایسه مقدار کربنات کلسیم (میانگین: 12.4%، دامنه: 7-26%) با پارامترهای مقاومتی نشان می‌دهد که همبستگی آن با چسبندگی و زاویه اصطکاک ضعیف و از نظر آماری معنادار نیست (r = 0.12, p > 0.05). این یافته‌ها نشان می‌دهد که حتی در حضور نودول‌های کربناته، رفتار مقاومتی آبرفت نوع D در جنوب تهران عمدتاً تحت کنترل رطوبت است و ناهمگنی طبیعی نیز در تغییرپذیری پارامترهای آن مؤثر است، نه کربنات کلسیم. بنابراین، در طراحی‌های ژئوتکنیکی در جنوب تهران، باید سناریوهای رطوبتی بحرانی (به‌ویژه اشباع) به‌عنوان شرایط حاکم در نظر گرفته شوند، زیرا خاک در شرایط یکسان رطوبتی، رفتاری نسبتا یکنواخت از خود نشان می‌دهد.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

The Effect of Humidity and Calcium Carbonate on the Shear Strength of Type D Alluvium in Southern Tehran

نویسندگان [English]

  • Mehdi Talkhablou 1
  • Arash Mahmoudi 2
  • Dariush Fallah 1
1 Department of Applied Geology, Faculty of Earth Sciences, Kharazmi University, Tehran
2 Department of Civil Engineering, Faculty of Engineering, University of Bu-Ali Sina, Hamedan, Iran.
چکیده [English]

This study investigates the simultaneous effects of moisture content and calcium carbonate (CaCO₃) percentage on the shear strength of Type D alluvium in southern Tehran. Fifty soil samples were systematically collected from districts 11 to 20 at depths of 1.5-4.0 m, with sampling locations precisely mapped on the alluvial zoning map of Tehran (Figure 1). Laboratory tests were conducted under three controlled moisture conditions: 8, 14, and 31% (representing dry, intermediate, and saturated states, respectively). Results show that increasing moisture to saturation causes a significant reduction in shear strength: cohesion (c) decreases by 38.8% (from 5.20 kPa to 3.18 kPa), and the internal friction angle (φ) drops by 8.4° (from 25.5° to 17.1°). Mixed-effects regression analysis confirms that moisture content (β=–1.78, p<0.001) is the dominant predictor of cohesion, while calcium carbonate content (mean=12.4%, range:7–26%) shows no statistically significant correlation with shear strength parameters (r= 0.12, p>0.05). Notably, even in the presence of naturally occurring carbonate nodules (caliche), moisture remains the overriding factor controlling mechanical behavior. This study concludes that for geotechnical design in southern Tehran, critical moisture scenarios (particularly saturation) must be treated as governing conditions, as the soil exhibits relatively uniform shear response under identical moisture states contrary to common assumptions about the strengthening role of carbonate cementation

کلیدواژه‌ها [English]

  • Type D alluvium
  • Moisture Content
  • Calcium Carbonate
  • Shear Strength
  • Mixed-effects Regression Analysis

مراجع

[1] Berberian M, Qorashi M, Arzhang-Ravesh B, Mohajer-Ashjai A. Recent Tectonics, Seismotectonic, and Earthquake-Fault Hazard Study of the Greater Tehran region, Tehran Quadrangle Area. Tehran, Iran: Geological Survey of Iran. 1985. [In Persian]
[2] Japan International Cooperation Agency (JICA). The Study on Seismic Microzoning of the Greater Tehran Area in the Islamic Republic of Iran. Tokyo, Japan. 2000.
[3] Asghari E, Toll DG, Haeri SM. Triaxial Behaviour of a Cemented Gravely Sand, Tehran Alluvium. Geotechnical & Geological Engineering. 2003; 21(1): 1-28. doi: 10.1023/A:1022934624666
[4] Cheshomi A. Study of Mechanical Properties of Coarse Alluvial in Tehran Based on Usual Tests and Simple Mechanical Tool. Ph.D. Dissertation. Tarbiat Modares University. 2006. [In Persian]
[5] Fakher A, Cheshomi A, Khamechiyan M. The Addition of Geotechnical Properties to a Geological Classification of Coarse-Grained Alluvium in Apediment Zone. Quarterly Journal of Engineering Geology and Hydrogeology. 2007; 40: 163-174. doi: 10.1144/1470-9236/06-029
[6] Khan Mohammadi N. The Effect of Grain Shape and Size Variables on Soil Mechanical Parameters (Case Study of Coarse-Grained Alluvium in Tehran). Master of Science Thesis. University of Tehran. 2008. [In Persian]
[7] Ghanbari A. Study of Elastic Modulus of Alluvium Deposits in Southern Tehran. Scientific Quarterly Journal of Geosciences. 2009; 18: 3-8. doi: 10.22071/gsj.2010.56979 [In Persian]
[8] Cheshomi A, Fakher A, Khamechiyan M. Geology of Tehran Alluvium and Evaluation of Rieben Classification for Geotechnical Studies. Journal of Science University of Tehran. 2008; 34(2): 1-15. [In Persian]
[9] Haeri SM, Shahcheraghi SA, Shakeri R, Seiphoori A. Mechanical Behavior of a Cemented Gravely Sand under Monotonic and Cyclic Loading-Case Study of Tehran Alluvium. 8th International Congress on Civil Engineering, Shiraz, Iran. 2009. [In Persian]
[10] Baghban Golpasand MR, Nikudel MR, Uromeihy A. Effect of Engineering Geological Characteristics of Tehran’s Recent Alluvia on Ground Settlement due to Tunneling. Geopersia. 2014; 4(2): 185-199. doi: 10.22059/jgeope.2014.52718 [In Persian]
[11] Ramezannejad Elyerdi SR, Cheshomi A, Fakher A. Evaluation of Accuracy Geological Maps Related to Geographical Expansion of the Tehran Alluviums. 2nd International Geosciences Congress, Tehra, Iran. 2016. [In Persian]
[12] Asadzadeh Saghavaz O, Ghorashi M, Pourkermani M. The Role of Faults on Tehran Alluvial and its Impact on Resistance of Alluvial. Open Journal of Geology. 2017; 07: 1128-1139. doi: 10.4236/ojg.2017.78075
[13] Nouhi Oskoui R, Dabiri R, Amelsakhi M. Evaluation of Settlement in Soil Layers due to Liquefaction in Alluviums in South Eastern of Tehran. Journal of Civil Engineering and Urbanism. 2017; 7: 70-79.
[14] Fan Y, Zheng M, Wu J. A Study on the Shear Strength Characteristics and Microscopic Mechanism of Coal-Bearing Soil under Dry-Wet Cycles. Frontiers in Earth Science. 2023; 10: 1096980. doi: 10.3389/feart.2022.1096980
[15] Ahmad W, Uchimura T. The Effect of Moisture Content at Compaction and Grain Size Distribution on the Shear Strength of Unsaturated Soils. Sustainability. 2023; 15: 5123. doi: 10.3390/su15065123
[16] Ma S, Yao Y, Bao P, Guo C. Effects of Moisture Content on Strength and Compression Properties of Foundation Soils of Cultural Relics in Areas Flooded by the Yellow River. Frontiers in Materials. 2023; 10: 1186750. doi: 10.3389/fmats.2023.1186750
[17] Pham TA, Sutman M, Medero GM. Validation, Reliability, and Performance of Shear Strength Models for Unsaturated Soils. Geotechnical and Geological Engineering. 2023; 41: 4271-4309. doi: 10.1007/s10706-023-02520-7
[18] Niu G, Zhu X, Li J, Lu M, An L, Chen Z. Experimental Study on Shear Strength of Unsaturated Soil over a Wide Suction Range and Its Prediction. Rock and Soil Mechanics. 2023; 44: 3349-3359.
[19] ASTM D2487-17. Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System). 2017. doi: 10.1520/D2487-17
[20] ASTM D7928-21e1. Test Method for Particle-Size Distribution (Gradation) of Fine-Grained Soils Using the Sedimentation (Hydrometer) Analysis. 2021. doi: 10.1520/D7928-21E01
[21] ASTM D4318-17e1. Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils. 2017. doi: 10.1520/D4318-17E01
[22] ASTM D3080/D3080M-11. Test Method for Direct Shear Test of Soils under Consolidated Drained Conditions. 2011. doi: 10.1520/D3080_D3080M-11
[23] ASTM D1188-07. Test Method for Bulk Specific Gravity and Density of Compacted Bituminous Mixtures Using Coated Samples. 2015. doi: 10.1520/D1188-07R15
[24] ASTM D4373-21. Test Method for Rapid Determination of Carbonate Content of Soils. 2021. doi: 10.1520/D4373-21
[25] Patten ML, Newhart M. Understanding Research Methods: An Overview of the Essentials. Routledge. 2013. doi: 10.4324/9781315266312
[26] Chen L, Chen X, Yang X, Bi P, Ding X, Huang X, et al. Effect of Calcium Carbonate on the Mechanical Properties and Microstructure of Red Clay. Advances in Materials Science and Engineering. 2020; 2020(1): 5298186. doi: 10.1155/2020/5298186
[27] Hosseini M, Taromi M, Saeidi M, Soleimani V, Soltani Negar M. The Study of Cementation Level Effect on the Strength Characteristics and Shear Wave Velocity of Coarse-Grained Alluvium in Eastern Areas of Tehran, Iran. Journal of Engineering Geology. 2020; 14: 581-608. doi: 10.52547/jeg.14.4.581 [In Persian]
[28] Kang Q, Xia Y, Li X, Zhang W, Feng C. Study on the Effect of Moisture Content and Dry Density on Shear Strength of Silty Clay Based on Direct Shear Test. Advances in Civil Engineering. 2022; 2022(1): 2213363. doi: 10.1155/2022/2213363
[29] Phoon K-K, Tang C. Characterisation of Geotechnical Model Uncertainty. Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards. 2019; 13: 101-130. doi: 10.1080/17499518.2019.1585545 
ارسال نظر در مورد این مقاله
CAPTCHA Image
پژوهش های زیرساخت های عمرانی

مقالات آماده انتشار، پذیرفته شده
انتشار آنلاین از تاریخ 07 دی 1404

فایل ها

هم رسانی

ارجاع به این مقاله

آمار