A dynamic damage constitutive model for a rock mass with non-persistent joints under uniaxial compression

Lat. Am. j. solids struct.

et al. 2020

The static and dynamic compression mechanical properties of the prefabricated artificial filled rock joints specimens with different fillings and different joint thicknesses are tested, respectively. Then, the strength, deformation, wave propagation and energy dissipation laws of the filled joints are analyzed. The experimental results show that the static and dynamic compression strength of filled joints increases with the strength of filling materials while decreases with the filling thickness. The deformation characteristics of filled joints under static and dynamic compression are positively correlated with the properties of filling materials and the thickness of filled joints. With the increasing of the filling thickness, the reflection coefficient increases while the transmission coefficient decreases. With the increase of the strength of the fillings, the reflection coefficient decreases while the transmission coefficient increases. The energy dissipation ratio decreases with the increase of the filliing thickness and increases with the increase of the strength of the filling material.

Section: Introductionmentioning

confidence: 99%

Experimental Study on Static and Dynamic Compression Mechanical Properties of Filled Rock Joints

Chai

Lat. Am. j. solids struct.

et al. 2020

“…These defects will evolve and develop under the action of external load, resulting in the strength reduction and performance deterioration of rock (Liu et al., 2018). Therefore, the constitutive model based on the damage mechanics theory accords with the characteristics of rock (Chan et al., 1997; Chen and Qiao 2018; Liu and Su 2016; Sun et al., 2018). In damage mechanics, the commonly used methods for defining the damage variable include the effective area method and the elastic modulus method (Krajcinovic and Silva, 1982; Krajcinovic and Sumarac, 1989; Sumarac and Krajcinovic, 1989; Wang et al., 2012).…”

Section: Creep Damage Constitutive Modelmentioning

confidence: 98%

Creep properties and damage constitutive model of salt rock under uniaxial compression

International Journal of Damage Mechanics

Zhang

Song

et al. 2019

101

To study the creep property of salt rock, uniaxial compression creep tests on salt rock specimens were carried out. The test results indicate that there is no steady creep of the salt rock used in this test in a strict sense. Even in the steady creep stage, the creep rate of salt rock changes continuously over time, but with a relatively smaller change range. When the axial stress does not exceed 9.5 MPa, the isochronous stress–strain curve of salt rock is approximately straight. While the axial stress exceeds 9.5 MPa, the isochronous stress–strain curve deflects to the strain axis, and the larger the axial stress, the more obvious the deflection. Thus, the long-term strength of the salt rock used in this test can be determined as 9.5 MPa. A mathematical expression for predicting the creep failure time of rock is proposed on the basis of assuming the change rule of rock strength over time conforms to the Usher function. Then starting from the variation in deformation modulus with respect to time in the creep process of salt rock, the elastic modulus of the damaged rock material is characterized by the deformation modulus, and the creep damage evolution equation of rock is established. Combined with the continuous damage mechanics theory, a new creep damage constitutive model for rock is proposed. The rationality of the model is verified using the uniaxial compression creep test results of salt rock. The results show that the new model can not only describe the attenuation and the steady creep of salt rock under low stress level, but also reflect the whole creep failure process under high stress level. The predicted curves under different axial stresses are all in good agreement with the test data.

“…Many studies have shown that before the appearance of macro-cracks due to loads, the mechanical properties of materials are affected by local micro-cracks (Chan et al., 1997; Ji et al., 2011; Liu and Su, 2016). According to the hypothesis of strain equivalence, the damage constitutive model of materials can be expressed as follows (Chen, 2020; Lemaitre, 1984; Xie et al., 2020) where trueE˜ is the elastic modulus of damaged materials, E is the elastic modulus of intact materials, and D is the damage variable.…”

Section: Damage Constitutive Model Of Salt Rockmentioning

confidence: 99%

Mechanical properties and damage constitutive model for uniaxial compression of salt rock at different loading rates

International Journal of Damage Mechanics

Zhang

Song

et al. 2021

To study the effect of loading rate on the mechanical properties of salt rock, uniaxial compression tests and acoustic emission tests at different loading rates were carried out on salt rock specimens. The test results show that with increases in loading rate, the peak stress of salt rock increases first and then essentially remains unchanged, and the elastic modulus increases gradually, while the strain at peak stress decreases gradually. Moreover, the Poisson’s ratio is independent of loading rate. The macroscopic failure modes of the salt rock specimens at different loading rates are all ‘X’-type conjugate shear failure. However, the loading rate is closely related to the degree of fracture, such that the smaller the loading rate is, the higher is the degree of fracture of salt rock. In order to describe the stress–strain behaviour in the process of salt rock failure, a damage variable expression represented by the deformation modulus was proposed, and a rock damage constitutive model was established according to the theory of continuum damage mechanics. The rationality of the damage constitutive model was verified by using the present uniaxial compression test results of salt rock and existing test data from the literature. The results show that the model can accurately describe the stress–strain response of rock in the failure process.