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Author: Admin | 2025-04-28
The state of air drying. Use the following formula to calculate: where: ρd—rock density (g/cm3); md—sample weight (g); A—mean area (cm2); H—mean height (cm).② Uniaxial compression testObjective: To measure the compressive strength, elastic modulus, and Poisson’s ratio of rock. In detail, the loading speed is 4 mm/800 s; adopt the load parameter is 5 kN/grid; the displacement parameter is 0.02 mm/grid; the uniaxial compressive strength of rock is calculated according to the following: where: R—Uniaxial compressive strength of rock, MPa; P—Maximum damage load, kN; A—The cross-sectional area of the sample perpendicular to the loading direction, cm2.③ Splitting tensile testObjective: To measure the tensile strength of rock. The specification: Diameter × height = 50 mm × 50 mm; the loading speed is 5 mm/50 s; The following formula is used to calculate the tensile strength of rock: σ t = 2 × P π × d × h (3) where: σt—Tensile strength of rock, (MPa); P—Maximum load at the time of failure, (kN); d—Diameter of the rock sample (cm); h—The height of the rock sample, (cm).④ Shear testObjective: The shear strength, cohesion, and internal friction angle of the rock were measured. The specification: Length × width × height = 50 mm × 50 mm × 50 mm; the loading speed: 5 mm/50 s; the load parameter: 5 kN/grid. The normal stress and shear stress on the shear plane of the specimen are calculated according to the following formula respectively: σ = P × ( cos α + f × sin α ) B × H × 10 (4) τ = P × ( sin α + f × cos α ) B × H × 10 (5) where: P—The axial pressure of rock failure, kN; B, H—The width and height of the block, cm; α—Clamp shear angle, degree; f—Friction coefficient of the roller, f = 0.According to the σ and τ values of each group of samples, the shear strength c and φ of regular rock blocks are calculated by the least square estimation method.⑤ Deformation testThe rock deformation test measures the longitudinal and transverse deformation of the sample under the action of longitudinal pressure and then calculates the elastic modulus and Poisson’s ratio of the rock.Four samples were prepared in each group; the sample size was 5 × 5 × 10 cm, and the height-to-diameter ratio was 2:1. The sample of rock uniaxial deformation test is saturated. The elastic modulus and Poisson’s ratio are calculated as follows: where: E, μ—Elastic modulus (MPa) and Poisson’s ratio; σ50—Equal to 50% compressive strength stress value, MPa; εd50—The longitudinal strain value at σ50; εh50—The transverse σ50 strain value at σ50.The compressive strength of the backfill (cement−sand ratio 1:12) was tested
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