Abstract
As an important property of rock material, brittleness plays a vital role in rock engineering. This paper raised the concept of elastic strain energy release rate and proposed an elastic strain energy release rate based brittleness index based on the most acceptable definition of brittleness. Mechanical and Nuclear Magnetic Resonance parameters of sandstone under various Freezing-Thawing (F-T) cycles are also acquired and analyzed. Then, the proposed brittleness index is used to compare with two recently proposed brittleness indices to verify its correctness and applicability. Finally, the brittleness index is applied to evaluate the brittle behavior of F-T cycles treated sandstone under uniaxial compression. The results show that elastic modulus, value of the postpeak modulus, and peak stress decrease with F-T cycles, and the porosity and microstructure develop with F-T cycles. The proposed brittleness index is highly related to F-T cycles, peak stress, porosity, and elastic modulus of sandstone that suffered recurrent F-T cycles. It declines exponentially with F-T cycles and porosity increase while growing exponentially with peak stress and elastic modulus increase.
Highlights
As a kind of geological weathering, Freezing- awing (F-T) cycles occur in many environments and usually cause negative effects in the real world
Physical and Mechanical Parameters. rough the uniaxial compression test and NMR test, mechanical parameters and physical parameters of the samples subjected to the recurrent F-T cycles were obtained. e physical parameter measured through NMR system in this paper is porosity, characterizing the inner damage and defects of the sandstone samples
Mechanical parameters obtained through the uniaxial compression test include elastic modulus, value of the postpeak modulus, peak stain, peak stress, residual stain, and residual stress
Summary
As a kind of geological weathering, Freezing- awing (F-T) cycles occur in many environments and usually cause negative effects in the real world. Brittleness is an important mechanical parameter that has a strong influence on the deformation and failure process of rock and on rock mass response to mining activities and slope engineering. It characterizes the brittleness of rock, and it is a complex property that is hard to be defined and calculated. Hucka and Das [4] proposed four definitions of brittleness and pointed out their deficiency. Meng et al [5] pointed out the most acceptable and understandable definition of brittleness, which is material terminating by fracture only slightly beyond the yield stress. Due to the complexity of brittleness description, uniform definition of brittleness has not formed yet
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