Beijing Key Laboratory of Urban Underground Space Engineering, University of Science and Technology Beijing
Civil and ResourceEngineering School, University of Science and Technology Beijing

In order to study the fatigue behavior of porous weakly cemented siltstone, a quantitative calculation method ofcharacteristic stress was established based on uniaxial step loading and unloading tests of siltstone. Then uniaxial cyclicloading and unloading tests of constant amplitude were carried out to study the volumetric strain, bulk compliance, andacoustic emission evolution of siltstone where the upper limit stress was in different stress ranges. The new method separatesvolumetric strain into the linear elastic strain of solid-phase dominated by rock skeleton, the non-linear elastic strainof gas-phase dominated by void, and the irreversible plastic strain. The peak points of gas-phase and plastic volumetric strain are taken as crack closure stress and crack initiation stress, besides the points of gas-phase volumetric strain and totalvolumetric strain changes from positive to negative are taken as crack damage stress and absolute dilatation stress, solvingthe problem that the calculation of characteristic stress is affected by subjective factors. The crack damage stress and absolutedilatancy stress determined by the new method can be regarded as the threshold stress of low-cycle and high-cycle fatiguefailure. When the upper limit stress is lower than the crack damage stress, the continuous friction and slippagebetween the skeleton particles and the microstructure rearrangement under cyclic loading and unloading result in the specimenbeing gradually compressed. As the times of cyclic loading-unloading increase, the residual volumetric strain, bulkcompliance, and cumulative acoustic emission count tend to be stable. When the upper limit stress is higher than the crackdamage stress, due to the generation of a large number of cracks, the residual volumetric strain and bulk compliance continueto decrease while the cumulative acoustic emission count continues to increase, resulting in a fatigue failure of thespecimen. The change of bulk compliance from positive to negative can be regarded as the early precursor of fatigue failure.The number of acoustic emission events NAE and k are approximately in a logarithmic-linear relationship. On thisbasis, it is proposed slope to describe the fracture pattern. The sudden increase of can be regarded as the early precursorand critical precursor of fatigue failure.

梁明纯，苗胜军，蔡美峰，等. 多孔弱胶结粉砂岩疲劳强度确定方法及疲劳破坏先兆[J]. 煤炭学报，2023，48（4）：1476−1486.
LIANG Mingchun， MIAO Shengjun， CAI Meifeng， et al. etermination method of fatigue strength and precursors of fatigue failure of porous weakly cemented siltstone[J]. ournal of China Coal Society，2023，48（4）：1476−1486.

LIANG Mingchun，MIAO Shengjun，CAI Meifeng，et al. Determination method of fatigue strength and precursors of fatigue failure of porous weakly cemented siltstone[J]. Journal of China Coal Society，2023，48(4)：1476−1486