Experimental Simulation and Numerical Modeling of Deformation and Damage Evolution of Pre-Holed Sandstones After Heat Treatment

Abstract

The deformation and damage evolution of sandstone after heat treatment greatly influence the efficient and safe development of deep geothermal energy extraction. To investigate this issue, laboratory confined compression tests and numerical simulations were conducted on pre-holed sandstone specimens after heat treatment. The laboratory test results show that the failure modes are closely related to the heat treatment temperature, with increasing treatment temperature, the failure modes change from mixed and shear modes to a splitting mode. The cracks always initiate from the sidewalls of the hole and then propagate. The failure process inside the hole proceeds as follows: calm period, particle ejection period, rock fragment exfoliation period and rock failure period. The specimens have different final failure features for the entire rock after heat treatment, but have the same failure features inside the hole. These phenomena can be explained by numerical simulations. The numerical simulations reveal that the failure modes in the numerical results agree very well with those observed in the experimental results. The damage zone always occurs at sidewalls of the hole and then propagates to the entire rock affected by shear or tensile damage. From 20°C to 200°C, thermal effect may promote shear damage and restrain tensile damage, while from 200°C to 800°C, thermal effect promotes tensile damage and restrains shear damage. Notably, the damage zone near the sidewalls of the hole has the same distribution range and pattern. Finally, the differences in the mechanisms due to increasing heat temperature are evaluated using scanning electron microscope (SEM) observations.

Deformation Rules for Surrounding Rock in Directional Weakening of End Roofs of Thin Bedrocks and Ultrathick Seams

“…A bench designed independently by China University of Mining and Technology was adopted to establish a similar simulation test model in which a high-speed static strain collection system was used to record the changes in the pressure cell data during the mining process, changes in rock formation displacement were observed with digital photographic measurement technology, and a hydraulic loading system was used to pressurize the overlying rock strata. PhotoInfor [18][19][20], a practical software system for digital photography measurement developed by China University of Mining and Technology, was used for digital image analysis. e test system is shown in Figure 3.…”

Introduction to the Special Issue on Modeling and Simulation of Fluid Flows in Fractured Porous Media: Current Trends and Prospects

“…This research promotes a good understanding of the effects of hole density and confining pressure on failure and mechanical behavior of porous geomaterials. Yang et al [10] investigated the deformation and damage evolution of sandstone after heat treatment through laboratory confined compression tests and numerical simulations in the paper titled "Experimental simulation and numerical modeling of deformation and damage evolution of pre-holed sandstones after heat treatment." From 20 • C to 200 • C, thermal effect may promote shear damage and restrain tensile damage, while from 200 • C to 800 • C, thermal effect promotes tensile damage and restrains shear damage.…”