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Abstract In order to study the effect of natural weak plane on mechanical properties of rock，40 limestone intact specimens and specimens with the angle of natural continuous weak plane ranged from 53° to 90° are carried out longitudinal wave velocities，uniaxial and pseudo-triaxial compression. The tests indicate that：longitudinal wave velocities，dip of specimens with weak plane，and uniaxial compressive strength have no certain relationship. Failure modes of specimens have three types，sliding-failure along the weak plane，shearing-failure across the weak plane and comprehensive failure，when the angle of specimen with weak plane ranged from 65° to 80°，it takes place sliding-failure along the weak plane，its strength is obviously lower，when the angle of specimen with weak plane is less than 65° or greater than 80°，it takes place shearing-failure across the weak plane，the strength and the fracture angle approximately meet Coulomb strength criterion；Two specimens take comprehensive failure，the strength of comprehensive failure is between shearing-failure across the weak plane and sliding-failure along the weak plane. The filling material of weak plane of limestone is approximately to main body，which has same internal friction coefficient 0.944 with intact specimens. The material strength of 40 specimens that the strength of triaxial compression deducts confining pressure is between 30.3 and 177.1 MPa，the average is 121.3 MPa，the standard deviation is 32.6 MPa，which roughly conform to normal distribution；The orientation of the weakest plane of rock varies with specimen whose cohesion is significant difference，which makes significant different the strength and failure modes of triaxial compression.
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Received: 29 November 2010
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2011, Vol. 30 
