TY  - JOUR
A1  - Zhu, Zhennan
A1  - Tian, Hong
A1  - Kempka, Thomas
A1  - Jiang, Guosheng
A1  - Dou, Bin
A1  - Mei, Gang
T1  - Mechanical behaviors of granite after thermal treatment under loading and unloading conditions
JF  - Natural resources research / sponsored by the International Association for Mathematical Geology
N2  - Understanding the mechanical behaviors of granite after thermal treatment under loading and unloading conditions is of utmost relevance to deep geothermal energy recovery. In the present study, a series of loading and unloading triaxial compression tests (20, 40 and 60 MPa) on granite specimens after exposure to different temperatures (20, 200, 300, 400, 500 and 600 degrees C) was carried out to quantify the combined effects of thermal treatment and loading/unloading stress conditions on granite strength and deformation. Changes in the microstructure of granite exposed to high temperatures were revealed by optical microscopy. The experimental results indicate that both, thermal treatment and loading/unloading stress conditions, degrade the mechanical behaviors and further decrease the carrying capacity of granite. The gradual degradation of the mechanical characteristics of granite after thermal treatment is mainly associated with the evolution of thermal micro-cracks based on optical microscopy observations. The unloading stress state induces the extension of tension cracks parallel to the axial direction, and thus, the mechanical properties are degraded. Temperatures above 400 degrees C have a more significant influence on the mechanical characteristics of granite than the unloading treatment, whereby 400 degrees C can be treated as a threshold temperature for the delineation of significant deterioration. This study is expected to support feasibility and risk assessments by means of providing data for analytical calculations and numerical simulations on granite exposed to high temperatures during geothermal energy extraction.
KW  - Granite
KW  - Thermal treatment
KW  - Unloading
KW  - Mechanical properties
KW  - Micro-structure
Y1  - 2021
U6  - https://doi.org/10.1007/s11053-021-09815-7
SN  - 1520-7439
SN  - 1573-8981
VL  - 30
IS  - 3
SP  - 2733
EP  - 2752
PB  - Springer Science + Business Media B.V.
CY  - New York, NY [u.a.]
ER  -