Barton-Bandis model

The fracture parameters used in FRACOD models are listed in Table 2. The Barton-Bandis model has been applied to estimate the fracture properties for newly initiated fractures. 

Barton-Bandis model for newly Initiated fractures... 

The newly created fractures are also assumed to have the same friction angle and cohesion as the intact rock. Once sliding occurs, however, the cohesion will become zero. The dilation of the new fresh fracture is also estimated using the Barton-Bandis model. It is found that the dilation has major effect on the failure process. 

The equivalent continuum model used for the JNC model is developed by combining the crack tensor theory proposed by Oda (1986) and the constitutive model by Barton et al. (1985). This model simulates the anisotropy of the media by crack tensor theory and the non-linear mechanical and hydraulic behavior by the Barton-Bandis (BB) model. Thus, the properties are changed heterogeneously and anisotropically through the excavation process. The constitutive law is incorporated into the coupled THM code, THAMES (Ohnishi, et al., 1985). 

The Barton-Bandis (BB) model represents the change in the normal and shear stiffness due to the stress change by using JRC (Joint Roughness Coefficient) and JCS (Joint Compression Strength). By using the JRC and JCS (MPa) which is the mean values for each set /, the initial normal stiffness of joint, K i (MPa/mm), is calculated for each set /,... 

The mechanical and hydromechanical properties of the horizontal rock fractures were estimated using the Barton-Bandis Joint model (Barton and Bakhtar, 1983). In this context, the void aperture, by, is defined as the accessible volume per unit area of a fracture. The void aperture at a given effective normal stress is... 

The mechanically induced void aperture can be related to the current effective normal stress, tr, using Barton-Bandis hyperbolic normal closure model according to... 

The non-linear empirical Barton-Bandis (BB) joint model describes the Joint behaviour. The mean input values are given in Table 2. The initial mechanical aperture (o/ ,) at zero normal stress is calculated with the following empirical relationship (Bandise/a/. 1983) ... 

HM-analysis has been only considered for the medium-density case. The HM-modelling was performed with the UDEC-BB model. The empirical relations in the UDEC-BB model are described in Bandis et al. (1983) and Barton et al. (1985). The in-situ stress field (MPa) is described by the following equations (Nirex 1997c) ... 

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