A circular borehole with hoop cracks in the borehole wall in an infinite rock mass is subjected to compressive stress of 60MPa and confining stress of 30MPa. The borehole is also free from any internal hydraulic pressure. The cracks are parallel to the borehole walls. The material properties of the rock mass and fractures are the same as in Examples 1 and 3.
The cracks are found to propagate and coalesce in a complex pattern. Both mode I and mode II failures are involved. The fracture propagation finally forms breakouts which have a failure pattern similar to that observed in the laboratory tests and field observations.
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TITLE
Complex fracture propagation to form borehole breakouts
SYMMETRY -- Model symmetry
4 0.00 0.00
MODULUS - Poisson's Ratio and Young's modulus
0.25 0.40E+11
TOUGHNESS -- Gic and Giic
50. 1000.
PROPERIES -- mat, kn. ks,phi,coh
1 0.10E+13 0.10E+13 30.0 0.00E+00
SWINDOW -- xll,xur,yll,yur,numx,numy
-2.00 2.00 -2.00 2.00 30 30
STRESSES -- sxx,syy,sxy
-.30E+08 -0.60E+08 0.00E+00
ARCH -- nume,xcen,ycen,diam,ang1,ang2,kode,ss,sn
12 0.0 0.0 2.0 0.0 90.0 1 0.00E+00 -0.00E+06
FRACTURE -- nume,xbeg,ybeg,xend,yend,kode,mat
2 1.144703678 0.11024287 1.134231801 0.1897846735 1
FRACTURE -- nume,xbeg,ybeg,xend,yend,kode,mat
2 1.077165893 0.402757543 1.046463904 0.476878704 5 1
FRACTURE -- nume,xbeg,ybeg,xend,yend,kode,mat
2 0.936221036 0.667824956 0.887381223 0.73147424 5 1
FRACTURE -- nume,xbeg,ybeg,xend,yend,kode,mat
2 0.731474264 0.887381204 0.667824981 0.936221018 5 1
FRACTURE -- nume,xbeg,ybeg,xend,yend,kode,mat
2 0.476878732 1.046463891 0.402757572 1.077165882 5 1
FRACTURE -- nume,xbeg,ybeg,xend,yend,kode,mat
2 0.189784703 1.134231796 0.1102429 1.144703675 5 1
CYCL 10000
ENDFILE
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