Modeling spatial fracture intensity as a control on flow in fractured rock

Chen Chang Lee, Cheng Haw Lee, Hsin Fu Yeh, Hung I. Lin

Research output: Contribution to journalArticlepeer-review

32 Citations (Scopus)

Abstract

Spatial fracture intensity (P32, fracture area by volume) is an important characteristic of a jointed rock mass. Although it can hardly ever be measured, P32 can be modeled based on available geological information such as spatial data of the fracture network. Flow in a mass composed of low-permeability hard rock is controlled by joints and fractures. In this article, models were developed from a geological data set of fractured andesite in LanYu Island (Taiwan) where a site is investigated for possible disposal of low-level and intermediate-level radionuclide waste. Three different types of conceptual models of spatial fracture intensity distribution were generated, an Enhanced Baecher's model (EBM), a Levy-Lee Fractal model (LLFM) and a Nearest Neighborhood model (NNM). Modeling was conducted on a 10 × 10 × 10 m synthetic fractured block. Simulated flow was forced by a 1% hydraulic gradient between two vertical x-z faces of the cube (from North to South) with other boundaries set to no-flow conditions. Resulting flow vectors are very sensitive to spatial fracture intensity (P32). Flow velocity increases with higher fracture intensity (P32). R-squared values of regression analysis for the variables velocity (V/Vmax) and fracture intensity (P32) are 0.293, 0.353, and 0.408 in linear fit and 0.028, 0.08, and 0.084 in power fit. Higher R2 values are positively linked with structural features but the relation between velocity and fracture intensity is non-linear. Possible flow channels are identified by stream-traces in the Levy-LeeFractal model.

Original languageEnglish
Pages (from-to)1199-1211
Number of pages13
JournalEnvironmental Earth Sciences
Volume63
Issue number6
DOIs
Publication statusPublished - 2011 Jul

All Science Journal Classification (ASJC) codes

  • Global and Planetary Change
  • Environmental Chemistry
  • Water Science and Technology
  • Soil Science
  • Pollution
  • Geology
  • Earth-Surface Processes

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