Fractal Discrete Fracture Network Modeling of Radon Gas Concentration in Underground Tunnels Under Ksiaz Castle in Poland

Details

• Personal Author:
  Ajayi KM ; Fijalkowska-Lichwa L
• Description:
  The numerical modeling of radon concentrations in the fault zone of the underground excavations at Ksiaz Castle was conducted using a stochastic Discrete Fracture Network (DFN) model. Due to the difficulties related with obtaining the exact fractures in a rock mass, the novel approach used in this study incorporates the stochastic model with known site data. The analysis utilized a dataset comprising long-term measurements of 222Rn activity concentration and geodetic measurements for twelve faults in the Ksiaz unit. The parameters considered in the DFN model are: fracture length, Peclet number (Pe=0.1 and 1.0, respectively), advection velocities (from 10-8 m/s to 10-6 m/s and from range from 10-7 m/s to 10-4 m/s, respectively), radon diffusion (D=2.1× 10-61/s), radon decay constant (Lambda=1/s), and radon gas generation (q) along the fractures within the range of 1.5×10-3Bq/m3·s to 3.5×10-3 Bq/m3·s. The calibration process obtained the best ft when the radon generation rate was uniformly distributed through the rock mass in addition to incorporating a higher value of radon generation rate (q=3.0×10-3Bq/m3·s) where elevated radon concentrations have been measured. The modeling results also confirmed that the radon generation rate should always be higher where elevated radon activity concentrations were measured regardless of the measurement period. For the indicated "area" the radon generation rate should be higher from 25% to 37.5% between May-October and 18.5% to 40% between November-April. The influence of fracture zones on the recorded radon activity concentrations was noticeable up to a depth of 15 m. Within this range, the highest values of 222Rn activity concentration, ranging from 1,600 Bq/m3 to 2,000 Bq/m3, were consistently observed regardless of the season. However, as the depth increased, the values of 222Rn activity concentration decreased from 800 Bq/m3 to 400 Bq/m3 and became more dispersed. [Description provided by NIOSH]
• Subjects:
  Occupational Health Safety
• Keywords:
  222Rn Activity Concentration Measurements Author Keywords: Discrete Fractal Network (DFN) Model Excavations Faults Fracture Zones Geotechnical Engineering Radon 222 Radon Gas Rock Mechanics Stochastic Methods Underground Construction Underground Tunnels

  More +
• Series:
  Mining Publications
• ISSN:
  1435-9529
• Document Type:
  Text
• Genre:
  Journal Article
• Place as Subject:
  OSHA Region 3 ; Pennsylvania
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  PMRD - Pittsburgh Mining Research Division
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Volume:
  83
• NIOSHTIC Number:
  nn:20069825
• Citation:
  Bull Eng Geol Environ 2024 Jun; 83:273
• Contact Point Address:
  Lidia Fijalkowska-Lichwa, Faculty of Civil Engineering, Wroclaw University of Science and Technology, Wybrzeze S. Wyspianskiego 27, Wroclaw 50 -370, Poland
• Email:
  lidia.fijalkowska-lichwa@pwr.edu.pl
• CAS Registry Number:
  Radon (CAS RN 10043-92-2)
• Federal Fiscal Year:
  2024
• Peer Reviewed:
  True
• Source Full Name:
  Bulletin of Engineering Geology and the Environment
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:8b393d26067560a9556e31aacc790245265267805013b5a851a20017ff441193d9b54c8b1013900b1a55d130070a3876cc509f9334931ad2be5e401964e71d04
• Download URL:
  https://stacks.cdc.gov/view/cdc/215704/cdc_215704_DS1.pdf
• File Type:
  [PDF - 2.94 MB ]