关键词: 磷块岩　, 变角剪切试验　, 力学特性　, 剪切破坏　, 改进Hoek-Brown准则

Abstract: Shear failure is one of the most common failure types in phosphate rock masses,and the shear angle signifi cantly influences its failure characteristics.A series of standard rock samples were prepared from the phosphate ore layer of the Second Phosphate Mine in Kunyang,and uniaxial compression,Brazilian splitting,and variable-angle shear tests were conduc ted to investigate the influence mechanism of the shear angle on the mechanical properties and failure modes of phosphorite. Based on the basic mechanical parameters obtained from laboratory tests,the rock brittleness was evaluated using the post-peak stress reduction rate of the full stress-strain curve and the ratio of the energy released at failure to the total energy stored before the peak.The basic mechanical parameters of the phosphorite rock mass were subsequently determined.The results indicate that:① With increasing shear angle,the normal stress,shear stress,rock strength,and peak load gradually decrease,and the stages of the stress-strain curve tend to shorten.In terms of failure morphology,at small shear angles,the rock undergoes ten sion-shear mixed failure with overall fragmentation;at large shear angles,shear failure dominates,and the failure surface is rela tively smooth.② The shear stress-displacement curve of phosphorite under compression-shear failure can be divided into three stages:compaction,elastic,and plastic deformation,which is similar to the full stress-strain curve under uniaxial compression. At the same shear stress level,the shear deformation stage of the specimen varies with the shear angle.③ The GSI value was determined based on a modified RMR method,and the empirical parameters in the Hoek-Brown criterion were improved ac cordingly to estimate the mechanical parameters of the phosphate ore layer.Compared with traditional methods,the mechanical parameters obtained by this approach are more accurate and consistent with engineering practice,providing an important referenceforengineeringdesignandconstruction.

Key words: phosphoriterock,variableangleshear test,mechanicalproperties,shear failure,improveHoek-Browncriteri on