|
Abstract Brittleness index and crack initiation stress，as the intrinsic reflection of mechanical properties for rock，reflect the heterogeneity and structural differences of rocks. Supposing that there exists a certain inevitable relationship between them，theoretical research and case study are conducted. Firstly，28 kinds of basic brittleness testing methods，based on ratio of uniaxial compressive strength to tensile strength，the whole stress-strain characteristics and hardness or soundness，are summarized. Secondly，the crack initiation mechanism for brittle rocks under uniaxial compression is studied. The method to determine crack initiation stress level is discussed by means of inflection points of crack volume strain curve；and the crack initiation stress level is defined as K. Finally，two cases are given to expose the function relationship between crack initiation stress and brittleness indices. Some conclusions are drawn as follows：(1) Based on the achievement of predecessors，by using the uniaxial compressive and tensile strengths，it is found that there exists a certain relation between crack initiation stress level and brittleness indices. (2) There are obvious function relationship between crack initiation stress level and brittleness indices B5，B6. To B5 is power function relation，and to B6 is linear function relation. The correlation coefficients are both greater than 85%，showing a strong correlation. (3) Brittleness index is redefined by crack initiation stress level，which can be obtained easily and quickly based on crack initiation stress level under uniaxial compression test. This study enriches the relationship between crack initiation stress and brittleness indices，and provides a new idea to determine the brittleness indices.
|
|
Received: 13 March 2013
|
|
|
|
2014, Vol. 33 
