JINX is a computer program for discrete fracture modeling of fractured rock masses for rock mechanics and hydrologic applications. The program incorporates conceptual models for fracture geometry based upon disks, polygons, and serially defined polygons with terminations at both fracture intersections and within intact rock. This paper describes the features of the JINX program and its application to practical problems.


The discrete fracture network modeling package JINX (Joints in Networks) was developed originally at the Massachusetts Institute of Technology under the sponsorship of the Army Research Office (ARO), and has since been extended by Golder Associates under the sponsorship of the Battelle-Office of Waste Technology Development (OWTD) of the U.S. Department of Energy Repository Technology Program (RTP). The program was designed to facilitate rock mechanics and hydrologic modeling of two and three dimensional discrete fracture networks. The discrete fracture network modeling approach has been implemented by a number of researchers over the past five years (Dershowitz, 1979; Long, 1983; Dershowitz, 1984; Robinson, 1985). The basic assumption of the approach is that the properties of fractured rock masses are determined by the behavior of individual fractures rather than by the rock mass as a continuum. As a result, the rock mass is modeled as a network of discrete elements representing the fractures (Figure 1). This approach has been applied to rock slope stability (see e.g., Einstein et.al, 1979), rock tunnel stability (Goodman and Shi, 1984), rock mass deformation (Dershowitz and Einstein, 1980), and more recently to groundwater flow (Long et al, 1985) and solute transport (Smith, Mase, and Schwartz, 1985). The approach of all of these models has been to define the rock mass by a specific conceptual model for rock fracture geometry, such as two dimensional Poisson (random) fibers, or Poisson disks. The philosophy of the of the JINX fracture network modeling package is to provide a common model within which many different conceptual models can be evaluated, under the assumption that different conceptual models are appropriate for different rock masses. At present, seven conceptual models have been implemented. For all of these models, JINX allows the same rock mechanics and hydrological analyses to be carried out.


  • The disk model (Figure 1) (Baecher, Lanney, and Einstein, 1978) in which fractures are represented by randomly located circular or eltpttcal disks.

  • The Veneztano (1979) polygon model (Figure 2), in which polygonal fractures are defined by a process of random (Potsson) lines on planes oriented according to any desired orientation distribution. Polygons on each plane are defined independently, so that there is no facility for defining fracture terminations at intersections.

  • The fracture model defined by Dershowitz (1984) (Figure 3), in which polygonal fractures are defined on fracture planes by a process of Poisson lines resulting from the intersection of fracture planes. This model can model fracture terminations at fracture intersections or intact rock, but requires that fracture termination and size be defined indirectly through the intensity of fracture planes.

The fundamental assumption of the JINX package is that different rock masses require different rock mass conceptual models. Figures 1 through 4 present the conceptual models implemented to date:

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