Mechanical Behaviors of Granite after Thermal Shock with Different Cooling Rates

Peng Xiao,Jun Zheng,Muhammad Kashif,Hong Tian,Bin Dou,Guodong Cui

doi:10.3390/en14133721

Abstract

During the construction of nuclear waste storage facilities, deep drilling, and geothermal energy development, high-temperature rocks are inevitably subjected to thermal shock. The physical and mechanical behaviors of granite treated with different thermal shocks were analyzed by non-destructive (P-wave velocity test) and destructive tests (uniaxial compression test and Brazil splitting test). The results show that the P-wave velocity (VP), uniaxial compressive strength (UCS), elastic modulus (E), and tensile strength (st) of specimens all decrease with the treatment temperature. Compared with air cooling, water cooling causes greater damage to the mechanical properties of granite. Thermal shock induces thermal stress inside the rock due to inhomogeneous expansion of mineral particles and further causes the initiation and propagation of microcracks which alter the mechanical behaviors of granite. Rapid cooling aggravates the damage degree of specimens. The failure pattern gradually transforms from longitudinal fracture to shear failure with temperature. In addition, there is a good fitting relationship between P-wave velocity and mechanical parameters of granite after different temperature treatments, which indicates P-wave velocity can be used to evaluate rock damage and predict rock mechanical parameters. The research results can provide guidance for high-temperature rock engineering.

Highlights

The utilization of fossil energy has several worrisome environmental implications, such as the greenhouse effect and acid rain
Mechanical of granite subjected to twovelocity different and ro there is athe good fittingbehaviors relationship between
P-wave thermal shocks have been studied based on mechanical experiments and an ultrasonic test mechanical parameters, so we can use the P-wave velocity test as a nondestructive ro technique

Summary

Introduction

The utilization of fossil energy has several worrisome environmental implications, such as the greenhouse effect and acid rain. In these circumstances, replacing gas and oil combustion with renewable energy resources can significantly reduce CO2 emissions and environmental pollution [1,2,3]. Clean renewable energy is the future direction of energy development and is attracting more and more attention [2,4]. Geothermal energy is a pollution-free and renewable energy source that has achieved rapid development [4,5,6]. During deep geothermal energy exploitation, it is important to circularly pump a working fluid into an underground fracture network to realize heat extraction. Hot dry rocks (HDR) with a temperature up to 400 ◦ C in a deep geothermal reservoir may be directly exposed to cool water and suffer great temperature gradients [8,9]

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Conclusion