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Investigating Ground Cave-ins and Subsidence due to Damaged Sewer Pipelines

Explore mechanisms of ground cave-ins and subsidence from damaged sewer pipelines. Review literature, propose research plan, and summarize findings.

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Investigating Ground Cave-ins and Subsidence due to Damaged Sewer Pipelines

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  1. 2015 Wednesday Seminar Investigation on Mechanism of Ground Cave-ins and Subsidence induced by Damaged Sewer Pipelines Geotechnical and Geoenvironmental Engineering Laboratory 2015.03.18(Wed) Ph D. candidate Kwak, Tae-young

  2. CONTENTS Introduction 1 Literature Review 2 Research Plan 3 Summary 4

  3. Introduction

  4. Introduction Background Seoul, 2014 - Length8m - Width2.5m - Depth5m Guatemala, 2010 - Diameter 20m - Depth30m

  5. Introduction Background (September, 2014, ‘Sink HoleAssessment and Countermeasures‘, Policy forum) 854 689 573 435 - Annual occurrences of ground cave-ins have increased. - Research for ground cave-ins needed.

  6. Introduction Ground Cave-ins and Subsidence (Sink Hole) : Depression or hole in the ground caused by some form of collapse of the surface layer

  7. Introduction Types of Ground cave-ins and subsidence 1. Inherent ground cave-ins : Development of cavities by dissolution of limestone by groundwater 2. Artificial ground cave-ins : Development of cavities by 1) Ground excavation , 2) Damaged pipelines (September, 2014, ‘Sink HoleAssessment and Countermeasures‘, Policy forum) Ground cave-ins and subsidence are induced by groundwater seepage and soil leaking through damaged sewer pipelines

  8. Literature Review

  9. Literature Review Ground Cave-ins and Subsidence by Excavation • Nakai et al. (1997) • : Comparison between model tests and numerical analyses by evaluating • the surface settlement • Type of soils (Dry toyoura sand & Kaolin clay) • Height of tunnel (D/B)

  10. Literature Review Ground Cave-ins and Subsidence by Excavation • Lee et al. (2006) • : Comparison between centrifuge tests and numerical analyses by • evaluating the surface settlement • Number of tunnels (Single-tunnel / Parallel-tunnel) • Center to center distance (d) • Cover to diameter ratio (C/D)

  11. Literature Review Ground Cave-ins and Subsidence by Excavation • Coudron et al. (2006) • : Comparison between model tests and numerical analyses by evaluating • the surface settlement • Width of cavity • Height of cavity • Structure above soils

  12. Literature Review Ground Cave-ins and Subsidence by Damaged Sewer Pipelines Water Research Center (England) : Explanation on development of underground cavities by poor connections of sewer pipelines • Limitations of WRC • Explanation limited to the phenomena • of cavity development • No explanation given on mechanism of • ground cave-ins and subsidence • induced by damaged sewer pipelines

  13. Literature Review Ground Cave-ins and Subsidence by Damaged Sewer Pipeline Higashi et al. (2003), Kuwano et al.(2009), Mukunoki et al.(2009) : Simulation of ground cave-ins and subsidence by damaged sewer pipelines (By naked eye or X-ray Computed Tomography (CT))

  14. Literature Review Ground Cave-ins and Subsidence by Damaged Sewer Pipeline Higashi et al. (2003), Kuwano et al.(2009), Mukunoki et al.(2009) : Some limitations existing in researches performed in Japan (1) No consideration on the soils at site - Used typical soils (ex. Toyoura sands) (2) No consideration on the seepage pressure at site - Used arbitrary differential heads (3) No investigation on the mechanism of ground cave-ins and subsidence - Evaluated only the cavities and loosening sections of soils - Evaluated cavities and loosening sections of soils only at specific times

  15. Research Plan

  16. Research Plan Steps of Research

  17. Summary

  18. Summary • Annual occurrences of ground cave-ins (Sink holes) have been increasing recently. Consequently, research of ground cave-ins is needed. • Most of artificial ground cave-ins are induced by groundwater seepage and soil leaking through damaged sewer pipelines. • Many researches have performed the evaluation of ground cave-ins and subsidence by model tests and numerical analyses. However, they do not properly investigate the overall mechanism of the development of ground cave-ins and subsidence. • Evaluation of external deformation by model tests and internal deformation by DIA will be performed. ⇒ The mechanism of ground cave-ins will be investigated, and the prevention methods will be established and verified.

  19. 2015 Wednesday Seminar THANK YOU Geotechnical and Geoenvironmental Engineering Laboratory Any question?

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