Creep Characteristics of Different Saturated States of Red Sandstone after Freeze-Thaw Cycles

Abstract

To investigate the creep mechanical characteristics of rocks in different saturated states after freeze-thaw cycles, samples with different saturations (30%, 50%, 70%, 90%, and 100%) were selected for nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), and uniaxial compression creep tests. The internal microscopic damage of the rock sample and mechanical characteristics under long-term loading are analyzed after the action of freeze-thaw cycles. The test results show that, as the saturation increases, the T2 spectrum distribution shifts to the right. The spectrum area gradually increases as the porosity increases. The critical saturation of freeze-thaw damage occurs when the saturation increases from 70% to 90%. It can be seen from the SEM image that the number of pores inside the rock samples gradually increases with increases in saturation, leading to the appearance of cracks. Under long-term loading, the saturation has a significant influence on the time-efficiency characteristics of sandstone freeze-thaw. As the saturation increases, the creep deformation gradually increases. After reaching 70%, the axial creep strain increases significantly. The rate of creep is accelerated, the creep failure stress is reduced, and the creep time under the last level of stress is significantly increased. A modified viscous-plastic body is connected in series to the basic Burgers model, the freeze-thaw-damage viscous element is introduced, and the creep parameters are fitted using test data. The results will provide a reference for long-term antifreeze design for rock engineering in cold areas.

Mesoscopic Freeze-Thaw Damage Evolution Characteristics of Fractured Sandstone at Different Saturations

“…Subsequently, the quality control method involved placing the rock sample in a thermostatic chamber to make the water uniformly volatilize until the rock sample reached the necessary saturation, which was set to either 60%, 70%, 80%, 90%, or 100%. The setting method was described by Che et al [34]. The formula is as follows:…”

Triaxial Compression Fracture Characteristics and Constitutive Model of Frozen–Thawed Fissured Quasi-Sandstone

“…Figure 10 is based on the results of the freeze-thaw and static loading tests shown in Table 3. Using Equations ( 14), (22), and (23), the theoretical curves of the total damage constitutive model of quasi-sandstone with four single-fissured angles subjected to static loading after freezing-thawing at different temperatures were calculated, and they are compared in Figure 10 with the experimental curves.…”

“…Because performing a uniaxial compression test is relatively easy, most previous research has focused on the mechanical behaviour of samples under uniaxial compression. The following conditions have mainly been considered: freeze-thaw times [18][19][20], moisture content [21,22], the geometric distribution of prefabricated or natural fissures [23][24][25][26], and loading patterns, such as cyclic loading and static-dynamic loading [27][28][29][30][31]. In the test process, computed tomography scanning can be used to observe better the micropropagation law of the cracks in frozen-thawed rock [32,33].…”

Investigation on damage creep constitutive model of rock under the coupled effect of freeze–thaw cycles and loading

“…21,22 Components combination models are constructed by combining elastic, plastic, and viscous elements in various serial and parallel configurations to form a new creep model. [23][24][25][26] Yang et al 27 proposed a statistical damage constitutive model of ice-rich frozen sandstone which can describe the random distribution of internal defects during the creep process. Zhang et al 28 proposed a viscoelastic-plastic creep model of rock based on the rheological theory; the model can simulate the creep properties of saturated rock.…”

“…Zhang et al 28 proposed a viscoelastic-plastic creep model of rock based on the rheological theory; the model can simulate the creep properties of saturated rock. Che et al 29 conducted uniaxial creep tests on red sandstone under different saturation levels, and the Burgers model was improved by introducing freeze-thaw damage-viscous elements. In addition, with the intensification of the energy crisis, the energy reserves become a critical indicator for the sustainable energy supply capacity.…”