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Uniaxial compression mechanical properties and damage constitutive model of limestone under osmotic pressure

To study the influence of osmotic pressure on the uniaxial compression mechanical properties of limestone, uniaxial compression tests were carried out on limestone specimens under different osmotic water pressure. The test results show that with the increase of osmotic pressure, the closure strain, yield strain and peak strain of limestone gradually increase, while the closure stress, yield stress, peak stress and elastic modulus gradually decrease. To describe the stress-strain response of limestone during uniaxial compression failure, the concepts of compaction factor and osmotic pressure influencing factor were proposed, and a constitutive model of rock compaction stage was established by integrating the relationship between the compaction factor and osmotic pressure influencing factor and the tangent modulus of compaction section. On this basis, combining the continuum damage mechanics theory, and assuming that the rock micro-unit strength obeys the compound power function distribution, a constitutive model reflecting the uniaxial compression mechanical properties of rock under osmotic pressure was established by the statistical method. The rationality of the model was verified using the results of the uniaxial compression test of limestone under different osmotic pressures. The results show that the test results under different osmotic pressures are in good agreement with the theoretical curves, and the model in this paper can reflect the stress-strain response of limestone before its failure under different osmotic pressures.