Effect of engineering geological characteristics of Tehran’s recent alluvia on ground settlement due to tunneling

Document Type: Research Paper

Authors

Engineering Geology Division, Department of Geology, Faculty of Basic Science, Tarbiat Modares University.

Abstract

Ground settlement due to the shallow tunneling in urban areas can have considerable implications for aboveground civil
infrastructures. Engineering geological characteristics of the tunnel host ground including geotechnical parameters of surrounding soil,
groundwater situation, and in situ stress condition are amongst the most important factors affecting settlement. In this research, ground
settlement as a consequence of the excavation of the East-West lot of Tehran Metro line 7 (EWL7TM) has been investigated. This
tunnel has been drilled into Tehran’s recent alluvia composed of fine-grained and coarse-grained soils. Findings indicate that the finegrained
and coarse-grained soils do not have similar behavior during shallow tunnel excavation. In general, maximum settlements
(Smax) occurred in the cohesion-less soil is greater than cohesive soil. In some sections of tunnel, measured settlements are lower than
evaluated items, stemming from the lower volume loss (VL). Performance of TBM and localized cementation of Tehran alluvia in the
considered area have been regarded as significant reasons of occurred discrepancy. In other sections of tunnel, measured settlements
are greater than evaluated figures. According to relative thickness constancy of the overburden, this antithesis can be attributed to the
existence of old and obsolete underground spaces.

Keywords


Article Title [Persian]

تاثیر خصوصیات زمین شناسی مهندسی آبرفتهای جوان تهران بر نشست زمین در اثر حفر تونل

Authors [Persian]

  • محمدرضا باغبان گل پسند
  • محمدرضا نیکودل
  • علی ارومیه ای
گروه زمین شناسی مهندسی، دانشکده علوم پایه، دانشگاه تربیت مدرس
Abstract [Persian]

نشست زمین در اثر حفر تونل های کم عمق در مناطق شهری تاثیرات عمیقی را می تواند روی زندگی روزمره انسانها داشته باشد. عوامل زیادی بر نوع و مقدار این نشست موثر می باشند که از این میان خصوصیات زمین شناسی مهندسی محیط میزبان تونل شامل پارامتر های ژئوتکنیک خاک، شرایط آب زیرزمینی، شرایط تنشهای اولیه از جمله این عوامل است. در این تحقیق نشست زمین در اثر حفر تونل قطعه شرقی-غربی خط هفت مترو تهران مورد مطالعه قرار گرفته است. این تونل در داخل آبرفتهای جوان تهران حفاری شده است که متشکل از مصالح ریزدانه و درشت دانه می باشند. نتایج مطالعات نشان دهنده این است که خاکهای ریزدانه و درشت دانه رفتار یکسانی در برابر حفر تونل از خود نشان نمی دهند و عموماً نشست حداکثر (Smax) در خاکهای درشت دانه بیشتر از خاکهای ریزدانه است. در بخشهایی از تونل نشست واقعی (اندازه گیری شده) کمتر از نشست های پیش بینی شده است. عملکرد صحیح TBM و سیمانی شدگی موضعی در آبرفتهای این بخش از تونل می توانند دلیل این مسئله پذیرفته شوند. در بخشهای دیگری از تونل نشست های واقعی بیشتر از نشست های پیش بینی شده است که دلیل این مسئله می تواند در ارتباط با فضاهای زیرزمینی قدیمی و متروکه باشد.

Keywords [Persian]

  • نشست زمین
  • تونل
  • آبرفتهای تهران
  • زمین شناسی مهندسی
  • مترو تهران
  • خط هفت مترو تهران
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