Authors: Mahendra Singh N K Samadhiya Ajit Kumar Vivek Kumar Bhawani Singh
Publish Date: 2015/01/21
Volume: 48, Issue: 4, Pages: 1387-1405
Abstract
Rocks encountered at many underground construction sites are laminated and exhibit directiondependent strength behavior It is also a wellestablished fact that the strength varies in a nonlinear manner with confining pressure There is a need of strength criterion which could capture the nonlinearity as well as the anisotropy in the triaxial strength behavior of the rocks It is essential that the criterion should be simple and must involve minimum testing to the extent possible Further the parameters of the criterion should have wide acceptability among the geotechnical fraternity In the present study a nonlinear strength criterion for transversely isotropic rocks is presented Critical state concept Barton Int J Rock Mech Mining Sci Geomech Abstr 139255–279 1976 has been used to define the curvature of the criterion With a correctly defined curvature and starting from a reference point UCS it is possible to accurately assess the triaxial strength for given confining pressure An experimental study conducted on triaxial strength behavior of three types of anisotropic rocks namely phyllite slate and orthoquartzite has been discussed A data base comprising more than 1140 triaxial tests conducted worldwide on anisotropic rocks has been compiled Statistical evaluation of goodness of fit of the proposed criterion to the data base has been carried out Further the predictive capabilities of the proposed criterion have been evaluated by determining the error in estimation of triaxial strength if only few triaxial test data are available for determining the criterion parameters The data base has also been back analyzed to assess the critical confining pressure for anisotropic rocks Statistically the critical confining pressure for anisotropic rocks can be taken nearly equal to 125 times the maximum UCS obtained by applying load either parallel or perpendicular to planes of anisotropy It is concluded that reasonable estimates of the triaxial strength of anisotropic rock can be made through the proposed criterion using minimum amount of triaxial test data available
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