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MS THESIS- Suraj khadka.pdf (1.67 MB)

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A Numerical Study of the Coupled Geomechanical Processes in Sinkholes

Khadka, Suraj
http://orcid.org/0000-0003-1409-0011
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1532970968316002

Abstract Details

2018, Master of Science, University of Toledo, Civil Engineering.
Sinkholes are ground depression or collapses resulting from erosion of bed-rock or overlying geo-materials into the cavity. Sinkholes are occurring in an alarmingly increasing frequency around the world, posing a significant threat to public safety and infrastructures. Sinkhole mechanisms involve intricate chemo-mechanical and hydro-mechanical processes which need an elaborate understanding. Dissolution and suffusion are believed to be the key mechanisms behind the occurrence of sinkholes in karstic rocks and soil overlying karstic rocks, respectively, which may also be potentially enhanced by aggressive ground water acidity, presence of fissures or fractures, etc. The present study explores a coupled approach to model the chemo-mechanical processes involved in dissolution dominated sinkholes and the hydro-mechanical processes involved in the cover collapse type of sinkholes. The first part of the thesis presents a coupled chemo-mechanical approach to understanding the interaction of chemical reaction and mechanical deformation processes involved in sinkhole development, focusing on the involved dissolution kinetics and enhanced deformation processes around the cavity. Specific solution rate of the constituent minerals (limestone or dolomite) and specific surface area available for reaction are related via a chemo-mechanical coupling with the consideration of the potential weakening of rock materials due to dissolution. It is proposed that the specific surface is dependent on the plastic volumetric strain and the original available specific surface for dissolution. Boundary value problems are formulated around the cavity to simulate the progression of mineral dissolution and plastic deformation. The numerical results and the presented approach allow for the assessment of time-dependent progressive processes of dissolution dominated sinkhole formation and development in karstic rocks. The second part of the present study explores the cover-collapse type of sinkholes in which a critical mechanism is the growth and upward propagation of the cavity. A Mohr- Coulomb constitutive model is adopted which describes the strength evolution dependent on water drawdown induced erosion and quantifies the progression of soil displacement around the cavity. Parametric analyses of progressive deformation around the cavity as a function of several parameters like drop-down rate, overburden thickness, permeability, etc. are presented considering and neglecting the erosion mechanism, which clearly establishes internal erosion mechanism as the dominant mechanism behind such sinkholes formation. The shear stress adopted in the erosion equation is based on solid continuum which is a debatable approach and clearly future studies should incorporate the calculation of shear stress along the flow direction based on the fluid dynamics and flow rheology.
Liangbo Hu (Committee Chair)
Brian Randolph (Committee Member)
Eddie Chou (Committee Member)
136 p.
Civil Engineering
Sinkholes; chemomechanical, hydromechanical, coupling, specific surface area, erosion

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Citations

  • Khadka, S. (2018). A Numerical Study of the Coupled Geomechanical Processes in Sinkholes [Master's thesis, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1532970968316002

    APA Style (7th edition)

  • Khadka, Suraj. A Numerical Study of the Coupled Geomechanical Processes in Sinkholes. 2018. University of Toledo, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1532970968316002.

    MLA Style (8th edition)

  • Khadka, Suraj. "A Numerical Study of the Coupled Geomechanical Processes in Sinkholes." Master's thesis, University of Toledo, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1532970968316002

    Chicago Manual of Style (17th edition)

toledo1532970968316002
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