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Evaluating changes in the degree of saturation in excavation disturbed zones using a stochastic differential equation
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  • Yota Togashi,
  • Kazuki Mizuo,
  • Masahiko Osada,
  • Tadashi Yamabe,
  • Hiroshi Kameya
Yota Togashi
Saitama University, Saitama University

Corresponding Author:togashi@mail.saitama-u.ac.jp

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Kazuki Mizuo
Staff Service Engineering Corporation, Staff Service Engineering Corporation
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Masahiko Osada
Saitama University, Saitama University
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Tadashi Yamabe
Crown Institute, Crown Institute
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Hiroshi Kameya
OYO Corporation, OYO Corporation
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Deformation characteristics of sedimentary rocks significantly changed with the water content during drying. In tunnel construction, extremely small displacements such as geological disposal, are allowed. Therefore, the proper evaluation of such drying deformation phenomena is critical. In such scenarios, it is also essential to accurately assess water content changes in the rock masses. Furthermore, the excavation disturbed zone (EDZ) spreads around the tunnel owing to the excavation process. EDZ has a higher hydraulic conductivity than an intact rock mass. Therefore, it is essential to predict water content changes in EDZ within the scope of the drying deformation phenomena. In this study, we derived the exact solution to the Richards’ equation at the Neumann boundary, which can be used to describe the drying phenomena in sedimentary rocks. Using Japanese tuff, we conducted a permeability test and a mercury intrusion porosimetry test to obtain the water diffusion coefficient and verify whether their drying behavior can be described using the exact solution. Using the verified exact solution, we proposed a new stochastic differential equation that could be used to explain the local decrease in permeability and the increase in variations in EDZ, and applied the stochastic differential equation to 2D tunnel problem.
Mar 2022Published in Computers and Geotechnics volume 143 on pages 104598. 10.1016/j.compgeo.2021.104598