Abstract:Single discontinuity theory is used to analyze the change of rock mass strength with the discontinuity inclinations;and the relationship between them is set up to explain the compression results. Then the results are used to the slates from the engineering of the west route of South-to-North Water Transfer Project,and the modeling results accord with the experiment ones. Some conclusions are drawn from the analysis as follows:(1) the single discontinuity theory can explain the phenomena of uniaxial and triaxial compression test on the slates;and the results can be used to the engineering;(2) the compression strength gets the minimal value when the discontinuity inclination is 51.7°;then it will increase towards two sides till reaching to the intact rock mass strength;(3) the deformation forms change with the different discontinuity inclinations,and the specimen can be damaged by sliding along discontinuities,shear failure and the combination of the two modes;and (4) the failure mode changes from the combined failure to shear failure when the confining pressure increases. The increment of the discontinuities number brings little effects to the rock mass strength.