b Current responses to loading and unloading pressure with different intensities.
To characterize the stability and recoverability more directly, Fig. 9b demonstrates the current responses to loading and unloading pressure with different intensities.
While unloading, pressure release will lead to further transformation into amorphous Si or a mixture of bcc Si and rhombohedral Si phases depending on the unloading rate [19, 24].
Under the conditions of loading axial pressure, and unloading confining pressure (LAUC), the experimental results showed that, when the loading rates of the axial pressure were 0.10 kN/s, 0.14 kN/s, and 0.18 kN/s, the triaxial strength of the coal samples were 37.39 MPa, 39.52 MPa, and 45.68 MPa, respectively, which had increased by 5.7% and 22.2% with the increase in the loading rates.
In this study, the speed can be classified into three regions in text: the low speed region of unload confining pressure, the intermediate speed region and the high speed region.
Triaxial unloading confining pressure process was reducing confining pressure while increasing axial pressure.
Based on domestic-developed triaxial servo-controlled seepage equipment for thermal hydrological mechanical coupling of coal containing methane, an experimental study was carried out to investigate mechanical property and gas permeability of raw coal, under the situation of conventional triaxial compression and unloading confining pressure tests in different gas pressure conditions.
In accordance with the forcing process around the coal body of the protected coal seam, permeability experiments were performed under fixed axial displacement with unloading confining pressure (FADUCP) and fixed deviatoric stress with unloading confining pressure (FDSUCP) stress paths.
Cement sheath may deform plastically in the process of gas injection and lose airtightness if unloading casing pressure.
Some scholars have studied the mechanics and damage characteristics of sandy mudstone, metamorphic quartz sandstone and silty sandstone under triaxial compression and triaxial unloading confining pressure (Fang et al. 2015; Deng et al. 2016; Guo et al. 2016).
