Experimental study on crack propagation pattern and fracture process zone evolution based on far-field displacement...

Area of Science:

• Geotechnical Engineering
• Materials Science
• Rock Mechanics

Background:

• Understanding rock fracture mechanics is crucial for geological engineering and resource extraction.
• Characterizing the fracture process zone (FPZ) and crack propagation is key to predicting rock failure.
• Advanced imaging techniques are needed to visualize and quantify complex fracture phenomena.

Purpose of the Study:

• To investigate the length and migration velocity of the fracture process zone (FPZ) during rock loading and unloading.
• To analyze crack propagation patterns and velocities using digital image correlation (DIC) and scanning electron microscopy (SEM).
• To identify microscale features within the FPZ and their relation to crack behavior.

Main Methods:

• Utilizing digital image correlation (DIC) to measure far-field displacements and strains in rock specimens.
• Analyzing strain and displacement distributions to define distinct fracture zones (intact, crack propagation, FPZ).
• Employing scanning electron microscopy (SEM) to observe the microstructural characteristics of fracture surfaces.

Main Results:

• The fractured ligament was classified into intact, crack propagation, and FPZ based on displacement variations.
• FPZ length peaked at maximum load and subsequently decreased; FPZ migration velocity ranged from -48 to 1460 m/s.
• Crack propagation velocity varied between 24-700 m/s, with initial propagation regions showing more severe damage.

Conclusions:

• Rock fracture involves distinct zones with varying mechanical behaviors and microstructural features.
• The dynamic nature of the FPZ and crack propagation influences overall rock mass integrity.
• DIC and SEM provide complementary insights into the complex processes governing rock failure.