Study on the mechanical properties of unloading damaged sandstone under cyclic loading and unloading
Hengbin Zhang1,2, Lehua Wang3,4, Jianlin Li1,2
1Key Laboratory of Geological Hazards on Three Gorges Reservoir Area, Ministry of Education, China Three Gorges University, Yichang City, 443002, Hubei Province, China.
Scientific Reports
|May 5, 2023
Summary
Unloading confining pressure significantly damages sandstone, reducing its mechanical properties. Cyclic loading exacerbates this, with microcrack extension being a key failure factor.
Area of Science:
- Rock Mechanics
- Geotechnical Engineering
- Materials Science
Background:
- Understanding rock mechanical behavior under stress is crucial for geotechnical engineering.
- Stress disturbance and unloading confining pressure are common factors affecting rock stability.
- Previous studies have explored rock failure but a comprehensive analysis of cyclic loading effects on unloading damaged rock is needed.
Purpose of the Study:
- To investigate the mechanical properties of sandstone under stress disturbance and unloading confining pressure.
- To analyze the evolutionary characteristics of dissipated energy and propose damage variables for sandstone under cyclic loading and unloading.
- To examine micro-crack development in sandstone from a microscopic perspective.
Main Methods:
- Conventional triaxial compression tests.
- Triaxial compression tests on unloading damaged sandstone.
- Cyclic loading and unloading tests on unloading damaged sandstone.
- Microscopic analysis of crack development.
Main Results:
- Sandstone exhibits brittle failure, primarily shear failure, under various stress paths.
- Cyclic loading significantly reduces load-bearing capacity, elastic modulus, and deformation modulus, especially with greater unloading damage.
- Unloading confining pressure is the dominant factor in specimen failure, with microcrack extension, particularly intergranular cracks, increasing with unloading quantity.
Conclusions:
- Cyclic loading and unloading tests reveal the complex mechanical response and fracture evolution of damaged sandstone.
- Unloading confining pressure is identified as the primary cause of failure, more so than cyclic loading itself.
- The findings provide insights for improving structural stability in environments with stress disturbance and unloading confining pressure.
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