## 3 Analysis of Experimental Results  
This study incorporates peak strength datasets from twelve distinct transversely isotropic rock formations, encompassing diverse lithologies and confining pressure conditions, to evaluate anisotropic strength criteria. The analyzed data draw from seminal experimental investigations including [PERSON] et al. [8]'s work on Bossier and Vaca Muerta shales, [PERSON] et al. [9]'s characterization of Angiers Schist, [PERSON] [9]'s analysis of Martinsburg Slate, and [PERSON] and [PERSON] [24]'s examinations of Austin Slate with Green-River Shale variants. Additional datasets derive from [PERSON] et al. [13]'s phyllite studies (Quartz, Carbona, and Micaceous types), [PERSON] and [PERSON] [9]'s Pernhyn Slate analysis, and [PERSON] et al. [9]'s Tournemire Shale experiments. All strength parameters are standardized in MPa units to enable direct lithological comparisons. These layered formations exhibit characteristic transverse isotropy--displaying quasi-isotropic behavior within bedding planes but marked directional dependence perpendicular to stratification. This mechanical anisotropy manifests in preferential failure along bedding planes under low-energy mechanical disruption, contrasting with enhanced resistance to cross-bedding deformation. The compiled datasets capture this fundamental anisotropy through controlled variations in bedding plane orientations relative to principal stress directions, providing a robust foundation for comparative analysis of strength criterion performance across geological materials.  
The strength of bedded rocks shows a transition zone at the relative angle between 0-\(\beta_{1}\) and \(\beta_{2}\)-90\({}^{\circ}\), wherein the failure mode is beyond the conception of the plane of weakness model, and is lower than both the intact rock and the plane of weakness in this transition caused by the mixed failure pattern.  
For relatively homogeneous lithological formations subjected to comparable confining pressure conditions, minimal strength disparity would be anticipated across different orientations. In contrast, transversely isotropic rocks demonstrate significant directional dependency, manifesting either U-curve or inverted V-shaped strength evolution patterns relative to bedding plane inclinations under equivalent confinement. This study's evaluation framework for twelve sets of peak strength predictions through anisotropic criteria necessitates preliminary quantification of lithological anisotropy. The coefficient of variation emerges as an effective statistical measure for characterizing material heterogeneity, particularly suitable for cross-comparisons between diverse lithotypes under varying confinement states. This dimensionless metric, derived from the ratio of the standard deviation to the arithmetic mean, enables standardized assessment of mechanical property fluctuations across measurement scales and unit systems, thereby facilitating analysis of stress-dependent anisotropic responses in stratified geological media.  
Figure 2 characterizes confinement-dependent anisotropy across twelve lithologies, all of which reveal a consistent pressure-sensitivity pattern, except for Micaceous Phyllite. The analyzed rock types demonstrate progressive anisotropy diminution with confinement reduction, exhibiting distinct pressure response phases: rapid anisotropy attenuation dominates at lower confining pressures, transitioning to pressure-insensitive behavior above critical confinement thresholds. Comparative analysis identifies Angiers Schist and Martinsburg Slate as exhibiting pronounced anisotropy, contrasting with Green River Shale variants showing the least anisotropic responses and minimal bedding angle sensitivity. Building on these lithological anisotropy profiles, subsequent analysis evaluates three dominant strength criteria against the experimental database to quantify their predictive capabilities in capturing confinement-modulated directional strength variations.