Abstract:The borehole penetrating method can rapidly and accurately test the uniaxial compressive strength(UCS) of coal and rock mass. Based on the principle of this method,the underground testing apparatus for coal and rock mass strength with small borehole is developed. 34 pieces of coal and rock blocks are tested. The standard samples are drilled from the coal and rock blocks. The uniaxial compressive strengths of the samples are measured;the critical load of the penetrating needle is measured with the testing apparatus in the reserved borehole;and the coal and rock damage patterns on the borehole walls are analyzed. Then the relation between the UCS of coal and rock blocks and the critical load of the penetrating needle is determined. The experiment points out that the forms,depths and scopes of the damage pits caused by the needle in the borehole walls are closely related with coal and rock properties;the higher the coal and rock strength is,the smaller the damage area and the penetrated depth are,and the more regular the pit form is. The formula describing the relation between the penetrating needle critical load and the UCS of coal and rock mass is obtained by the regression of laboratory data combined with underground measurement data. Meanwhile,the discrete property of the critical load and its controlling measures are analyzed;and the influence of structural planes on the coal and rock mass strength and its testing methods are discussed. The in-situ tests are carried out in typical deep coal mining area—Xinwen coal mines. There are great differences among the strengths of roadway roof strata with different lithological characters;and the strata strengths are also different in various coal mines. The coal seam strengths vary and fluctuate considerably along the test borehole because of the broken zone around coal sides,coal heterogeneity and nonuniform distribution of structural weakness planes in coal mass. The supporting designs accord with the coal and rock mass conditions in underground mines on the basis of the in-situ measurement of coal and rock strengths;and the rationality and reliability of the roadway supporting designs are improved remarkably. The stability of the surrounding rock and roadway supporting states are obviously improved. Finally,the present problems of the borehole penetrating method are analyzed;and the improvement proposals are put forward.