Mechanical Behavior of Shale Rock under Uniaxial Cyclic Loading and Unloading Condition

Abstract

In order to investigate the mechanical behavior of shale rock under cyclic loading and unloading condition, two kinds of incremental cyclic loading tests were conducted. Based on the result of the short-term uniaxial incremental cyclic loading test, the permanent residual strain, modulus, and damage evolution were analyzed firstly. Results showed that the relationship between the residual strains and the cycle number can be expressed by an exponential function. e deformation modulus E 50 and elastic modulus E S first increased and then decreased with the peak stress under the loading condition, and both of them increased approximately linearly with the peak stress under the unloading condition. On the basis of the energy dissipation, the damage variables showed an exponential increasing with the strain at peak stress. e creep behavior of the shale rock was also analyzed. Results showed that there are obvious instantaneous strain, decay creep, and steady creep under each stress level and the specimen appears the accelerated creep stage under the 4th stress of 51.16 MPa. Based on the characteristics of the Burgers creep model, a viscoelastic-plastic creep model was proposed through viscoplastic mechanics, which agrees very well with the experimental results and can better describe the creep behavior of shale rock better than the Burgers creep model. Results can provide some mechanics reference evidence for shale gas development.

Experimental Investigation of the Physical Properties and Microstructure of Slate under Wetting and Drying Cycles Using Micro-CT and Ultrasonic Wave Velocity Tests

“…After six cycles of wetting and drying treatments ( n = 6), the sample dry weight was reduced by 3.6, 5, 0.8, and 0.9 g for the four samples. The widely used empirical exponential equation for describing rock characterization and damage [ 4 , 45 , 46 , 47 ] was chosen for experimental data fitting. The results show that the relationship between sample weight and the number of wetting and drying cycles could be described satisfactorily by an exponential equation.…”

Mechanical Behavior and Damage Evolution for Granite Subjected to Cyclic Loading

“…erefore, all the damage parameters were only evaluated from the rst cycle to the last but one cycle in the literature [14,22]. However, it is known that the cumulative damage of the rock sample actually is not equal to 1.0 before the sample failure (i.e., before the last cycle).…”

Burger’s Bonded Model for Distinct Element Simulation of the Multi-Factor Full Creep Process of Soft Rock

“…Then, applying Burger's model into DEM, Li et al [14] studied the rheological behavior of soft rock; Guo et al [15] studied the time-dependent mechanics of sandstone. However, many creep tests of soft rock [14,[16][17][18][19][20] have shown that the full creep includes attenuated, steady, and accelerated creep. The classic Burger's model can only reveal the first two creep stages [21], which is weak in describing the damage process.…”